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Long-term stability and change in the commercial groundfish longline fishing grounds of the northwest Atlantic
ELSEVIER
Fisheries Research 25 (1996) 139-154
Long-term stability and change in the commercial groundfish longline fishing grounds of the northwest Atlantic T.J. Kenchington Gadus Associates, R.R. #I. Musquodoboit Harbour, N.S., BOJZW, Canada
Abstract The fishing grounds in the northwest Atlantic Ocean that were exploited by commercial groundfish longline boats in the 188Os, in about 1940 and in 1990 are compared and examined for evidence of changes in fish distributions over multi-decadal time scales. In general, the grounds fished were notably similar at the three times, the halibut grounds being particularly stable. Moreover, most of the changes detected can be attributed to developments in markets, regulations or similar human concerns. However, the known withdrawal of haddock from the former limits of its range is seen as a change in the areas fished for that species. There is also some evidence for shorter-term changes in cod abundance on grounds near the entrance to the Gulf of St. Lawrence. It is suggested that the general stability in the grounds fished is consistent with the potential productivity of the resources having also remained stable, despite the great increase in fishing effort during the last century. The common assumption of stability in productivity that is implicit in most stock assessments is therefore supported, except for those stocks that are near the limits of their species’ range. Ke.vwords: Fishing grounds; Historical development; Longline; Northwest Atlantic;
Productivity
1. Introduction
Fisheries stock assessment necessarily involves some prediction of a resource’s future response to fishing effort. Like all predictions, these are extrapolations from past conditions. In most cases, they rely on an assumption of continuing underlying stability, not in fish production but in potential productivity in the absence of fishing effort. Such an assumption is almost impossible to test. Given the importance of this stability assumption and the lack of adequate tests, even uncertain indications of long-term stability in resource populations, or of the absence of such stability, are of considerable interest. One potential indicator is fish distribution. 0165-7836/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved SSDlO165-7836(95)00414-9
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Stability in distribution need not indicate stability in productivity, but marked distributional change certainly suggests the local absence of that stability. Thus, studies of distribution cannot confirm, but may serve to falsify, the stability assumption. Appropriate scientific data on the distributions of marine resources, based on regular research vessel surveys, have only been collected for a few decades. To judge the degree of stability in productivity over multi-decadal time scales, it is necessary to resort to studies of the distribution, not of the fish themselves, but of the commercial fishing grounds. Where appropriate data are available, such as with the Scanian herring fishery, such studies have reached back for several centuries with considerable success (Cushing, 1982). The locations of commercial fishing grounds are controlled by many factors, but these can usefully be grouped into three classes: biological factors, the interactions between the fish and the fishing gear, and human/technical factors. Commercial fishing can only be carried out in places where fish of appropriate types and sizes are sufficiently concentrated. Hence, the locations of the grounds are partly determined by the distributions of the resources, which are themselves controlled by biological factors. It is not, however, sufficient for the fish to be present in an area. They must be available to the types of fishing gear used if that area is to be fished. The characteristics of the gear and their interactions with the behaviour of the fish will therefore partly determine the locations of the grounds, while the environment may influence these interactions (some gadoids will not take baited hooks set on a muddy bottom, for example: Kenchington and Halliday, 1994). Finally, some grounds which could be fished will not be because they are too distant from landing ports, too exposed to bad weather or subject to some other technical or human constraint that has no direct connection to resource biology. Of these three classes, the biological factors concern the distribution of the fish and hence are the information desired when examining long-term resource stability. The technical factors are matters of human decisions which may be recorded, interpreted and understood with relative ease. The interactions between fish behaviour, fishing gear and the environment are, however, both complex and, in almost all cases, unknown. It is therefore impossible to judge the stability or otherwise of the distribution of a fish stock by comparing, for example, the grounds exploited by longlining in some earlier period with those now fished by otter trawling, even were the same species and sizes of fish targeted in each case. Thus, the radical changes in fishing methods during the twentieth century usually prevent useful comparisons between modern fishing grounds and those of earlier eras. Conclusions about the stability of the resources under intense modern fishing pressures cannot often be built on distributional studies. In the northwest Atlantic groundfish fisheries, however, many fishermen still use longline gear ’ that is unchanged in its fundamentals from that employed by dory schooner fishermen in the second half of the nineteenth century. The types of boats from which this gear is set have changed completely in the last hundred years and there have been other developments, in fish marketing for example, which have affected fishermen’s behaviour. However, the only technological changes relevant to the interactions between the fish and the gear have ’ The type of demersal hook-and-line fishing that is generally known as ‘longlining’ is commonly referred to as ‘trawling’ by Atlantic Canadian and New England fishermen, who term otter trawling ‘dragging’. They also call longline snoods ‘gangions’. In this paper, I use the internationally recognized terms, converting as necessary from the terminology of cited sources, while 1 modernize all place names.
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been: the adoption of circle hooks and other modern hook designs, some minor changes in the relative frequencies of different bait types, a shortening of the typical lengths of the snoods, and the general adoption of synthetic materials (Kenchington and Halliday, 1994). None of these changes seems likely to have affected the catching process sufficiently to have altered the distribution of the fishing grounds. Indeed, for over a century the longline fishermen have maintained their preference for only five principal target species: Atlantic cod (Gadus morhua) , haddock (Melanogrammus aeglejks) , Atlantic halibut (Hippoglossus hippoglossus) and, to a lesser extent, white hake (Urophycis tenuis) and tusk (Brosme brosme: Rathbun, 1887; McKenzie, 1942; McKenzie, 1946a; McKenzie, 1946b; Kenchington and Halliday, 1994; Halliday and Clark, 1995). Their mode of fishing, and hence the relationship between their chosen grounds and the distribution of the fish, seems likely to have been equally constant. Kenchington et al. (1994) and Kenchington and Halliday ( 1994) have presented maps of the grounds fished by Nova Scotian groundfish longliners in 1990, based on data gathered through extensive interviews of fishing captains. They have also reviewed comparable published accounts (based on interview or logbook data) concerning grounds fished in the past three decades (Halliday et al., 1986; Halliday and Sinclair, 1987; Sinclair, 1992). Since completion of their work, however, some earlier sources of information have come to light. In particular, Rathbun ( 1887) published a detailed, and partially illustrated, account of the grounds fished by the New England schooner fleet in about 1880, while McKenzie (1942), McKenzie ( 1946a) and McKenzie ( 1946b) presented some information on the location of fishing by both Canadian and New England vessels in 1938-40. With these additional sources, it is now possible to judge the stability of groundfish longline fishing grounds in the Canadian portion of the northwest Atlantic (Fig. I ) from 1880 to 1940 and thence to 1990. It is fortunate that this comparison should be possible since this particular area is notable for its high degree of inter-annual environmental variation (Weare, 1977; Petrie and Drinkwater, 1993). If the assumption of constant resource potential productivity is an acceptable approximation in the waters from Cape Cod to Grand Bank, it seems likely to be adequate in routine stock assessment calculations in many other sea areas. In this paper, the information from Rathbun ( 1887), McKenzie ( 1942), McKenzie (1946a), McKenzie (1946b), Kenchington et al. (1994) and other relevant sources is evaluated. The grounds fished at various times are then examined for evidence ofthe changes in distributions that would refute the assumption of stable potential productivity. The grounds themselves are not described here since that information is available in the cited sources.
2. The available data 2.1. Fishing grounds exploited by New England schooner$shermen
in about 1880
As part of G.B. Goode’s monumental survey of the fisheries of the United States, Rathbun ( 1887) compiled information on the locations of the fishing grounds. His account contains information from as late as 1885, but it also contains remarks on some areas fished in the
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Fig. 1. Map of the northwest Atlantic showing place names used in the text. The Scotian Shelf grounds (banks) indicated by numbers are: 1, Misaine; 2, Middle; 3, Western; 4, Emerald; 5, Sambro; 6, LaHave; 7, Roseway. ‘C.B.I.’ indicates Cape Breton Island (a part of Nova Scotia). The bathymetric contours shown are for 100 and 200 m depth.
1850s. For the New England fisheries his data were gathered from various sources, but particularly from the personal experience and knowledge of Capt. J.W. Collins, who served as a form of technical advisor to Goode. The reliability of Collins’ reports cannot be confirmed but there is little reason to doubt their major features. Rathbun ( 1887) presented his information in a verbal format, supplemented by charts for selected areas only. The latter are summarized in Fig. 2. Since the comparative data from later periods are exclusively from waters off Canada, only information of Rathbun ( 1887) on grounds in that area is used here. With the exception of part of the Bay of Fundy, all such grounds are a considerable distance from United States’ ports. Hence these data are almost exclusively from the offshore schooner fishery, although Rathbun ( 1887) did provide some information on inshore fishing by Nova Scotians. In the 188Os, New England schooner fishermen made some trips to West Greenland and even a few to the Iceland grounds. These distant grounds are not considered further in this paper. By 1880, there had been cod fisheries in the northwest Atlantic for about 400 years. For most of that time, however, the fish had been caught by handlining, usually from small boats based at shore stations. There had been only a limited amount of offshore fishing, which was carried out by handlining from fishing ships and schooners (Balcom, 1977; Balcom, 1984). The French introduced longline techniques to the Grand Banks cod fisheries in about 1789, but their activity ceased with the outbreak of war 4 years later (De Loture, 1957). It was not until the early 1840s that their resumed longlining came to the attention
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[.,&! . ..I 70”
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Fig. 2. Map showing some of the grounds
I 60”
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fished in about 1880 by New England longline fishermen, re-drawn
fromthe chartspreparedby Rathbun ( 1887). The crosses indicatesomespecific locations where particularly good halibut catches were taken in the late 1870s or early 1880s. Rathbun’s disagreed with his text.
charts were incomplete
and in places
of local fishermen (Perley, 1852; Goode, 1887) when, in an independent development, some inshore fishermen of Massachusetts began to set halibut longlines. Over the next few years longline gear was adopted by many New Englanders for both cod and halibut (Goode, 1887). By the end of the 184Os, many fishermen in what is now Canada had also taken up the new gear (Perley, 1852). As longlining became accepted, the New England offshore schooner fishery also adopted dory fishing, in which the lines were worked from small boats ( ‘dories’), with the schooner acting as a mother ship. With this further technological change, the cod fishermen began to exploit the offshore banks to a much greater extent than had previously been possible, resulting in a major change in the grounds commonly fished (Goode, 1887; Rathbun, 1887). By 1880, therefore, the offshore dory longline fishery for cod had been established for over 20 years; sufficient time for the better grounds to be discovered and, given the preceding four centuries of related development, for the fishery to achieve a quasi-stable state. While some areas had yet to be fully explored (Rathbun, 1887)) in general the grounds fished for this species in about 1880 should have been those optimal for the fishery of the time, and no major differences in the cod grounds between 1880 and 1990 should have resulted from the nineteenth-century fishermen lacking knowledge of their fish. In contrast, the New England offshore fishery for halibut only began in the 186Os, and the prolific deepwater grounds along the continental slope were not discovered until the 1870s. It is clear from the account of Rathbun (1887) that in 1880 this fishery was still in
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a ‘fishing-up’ phase: the fleet moving on as the available biomass on each newly discovered ground dropped from virgin levels. In consequence, both the biology of the halibut resource and human knowledge of its distribution were in a state of flux in 1880. The grounds fished at that time need not, therefore, be directly comparable with those of later decades. Only a few grounds were fished for haddock, hake or tusk by the New England fleet in the 1880s. The fisheries for these species seem to have been limited by restricted markets and the difficulty of preserving these fish during a long voyage to the port of landing; unlike cod, they do not salt well. Thus, the data of Rathbun (1887) on these grounds are of restricted value for present purposes. 2.2. Fishing grounds exploited by the Canadian offshorejshery
in the late 1930s
Half a century after the work of Rathbun ( 1887)) McKenzie (McKenzie, 1942; McKenzie, 1946a; McKenzie, 1946b) published some information on the grounds fished by the few trawlers and the considerable fleet of offshore schooners which then operated from Canadian ports *. His data were largely drawn from interviews with fishing captains conducted from 1938 to 1940. While he largely confined his attention to Canadian offshore boats, McKenzie also provided some information on the local inshore fisheries and on United States’ fishing in waters off the Canadian coast. Unfortunately, he presented most of his distributional data by statistical unit areas, which give only a crude, and sometimes misleading, indication of the actual grounds fished. He did provide one more precise map showing the principal offshore grounds for haddock, and this is re-drawn here as Fig. 3. By the late 1930s the New England offshore groundfish fisheries had largely converted from longlining to trawling. The Canadian fishery, in contrast, still relied on dory fishing from schooners for all of its salt cod, for the great majority of its fresh cod and halibut caught offshore, and for more than half of the fresh haddock taken there. Many Canadian inshore boats were mechanized by the 1930s although they still relied on handlines and longlines for groundfish fishing. Except for the haddock fisheries, McKenzie did not clearly distinguish between the grounds fished by the fresh-fishing schooners and those worked by the steam trawlers. There were few of the latter, however (only three in 1938-39, although more in 1940)) and they appear to have concentrated on haddock (and perhaps other species not pursued by the schooners), so McKenzie’s (McKenzie, 1942; McKenzie, 1946b) descriptions of the cod and halibut grounds can be taken to represent those exploited by dory schooners. Some supplementary data are available for this same general period. Specifically, Needler ( 193 1) provided a brief summary and accompanying map of the haddock grounds fished in 1918-25, although she did not distinguish those fished with different gears. Later, Close (no date) published a chart of the northwest Atlantic fishing grounds and an accompanying booklet. Unfortunately, his work relied heavily on that of Rathbun ( 1887)) often quoting it verbatim and out of chronological context. Moreover, Close (no date) included information on the trawling grounds which is not of present relevance. However, he did record a few original observations on the halibut grounds fished in 1928 which are of value here. *Newfoundland was not then a pact of Canada. Thus, the ‘Canadian’ offshore fishery of the 1930s was almost exclusively based in Nova Scotian ports.
i? J. Kenchington / Fisheries Research 25 (1996) 139-154
145
50"
..
‘“L,_
“*;
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40”
_,/:‘.-
I 70”
__<.fl’
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Fig. 3. Map showing the grounds most frequently fished by Canadian offshore haddock fishermen in 1938-1940, re-drawn from Fig. 3 of McKenzie ( 1946a). Some of the fishing on Western and Emerald banks was by otter trawlers, but otherwise the grounds shown were fished by dory schooners working longline gear.
2.3.
Fishing grounds exploited by Nova Scotian longliners in I990
Kenchington et al. ( 1994) published maps of the grounds fished by groundfish longliners with home ports in Canada’s Scotia-Fundy Region ’ using data derived from a survey of fishing captains. Their boats included small craft under 7 m in length and large offshore longliners of over 40 m. Most, however, were between 10 and 14 m long. Kenchington and Halliday (1994) have provided a full report on this survey, during which more than 300 fishermen were interviewed, including additional details on the grounds fished. The maps of Kenchington et al. (1994) of the grounds are summarized here as Fig. 4. Those maps did not distinguish between grounds fished lightly and those fished intensively, while the interviews provided only limited data on the seasons in which, and the species for which, particular grounds were fished. Otherwise the maps, and hence the present figure, are thought to have captured a reasonable record of the distribution of longline grounds fished by this fleet in 1990. These various sources together provide all that is known to science, with any certainty and detail, about the locations of longline grounds in the northwest Atlantic, None of them describes all such grounds, however. Moreover, as McKenzie (1946a) and Kenchington and Halliday ( 1994) make clear, fishermen from various ports and those with different ’ The coastline of the Scotia-Fundy Region extends from the northern tip of Cape Breton Island, along the Atlantic coast of Nova Scotia and around the Bay of Fundy to the international border with the United States.
T.J. Kenchington / Fisheries Research 25 (1996) 139-154
146
50”
j.‘. ..
r‘..
‘.
..:
45”
_ 7,_~;.-“.r.E
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Fig. 4. Map showing the grounds fished during 1990 by groundfish longliners from Canada’s Scotia-Fundy Region, re-drawn from the figures presented by Kenchington et al. ( 1994).
sizes of boats usually choose rather different places to fish. Those selected by the fleets studied by Rathbun ( 1887), McKenzie ( 1942), McKenzie ( 1946a), McKenzie ( 1946b) and Kenchington et al. (1994) cannot, therefore, be fully comparable. No better evidence is available, however, and so a cautious comparison must be attempted.
3. A comparison of the grounds fished 3.1. Cod grounds In the early 1880s the late 1930s and again in 1990, the various cod longbne fleets considered here each fished a broad swathe from Georges Bank and the Bay of Fundy to Grand Bank, reaching north to about 48”N latitude in the 1880s although not quite so far in 1990. Grand Bank was the major cod ground for the New England schooner fleet in the 188Os, as it was for the Canadian salt-fish schooners of the 1930s and for the larger (over 20 m length) Scotia-Fundy Region longliners in 1990. The offshore banks of the Scotian Shelf were almost equal in importance to Grand Bank in the 188Os, they were the main centre for the Canadian fresh-cod fishery 50 years later, and were the principal grounds for the smaller Scotia-Fundy longliners of modern times. The more westerly banks seem to have been particularly consistently fished, although the Canadian schooner fleet of the 1930s largely left them to the New Englanders (Rathbun, 1887; McKenzie, 1942; Kenchington et al., 1994).
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Neither Rathbun ( 1887), McKenzie ( 1942) nor Kenchington et al. ( 1994) reported more than a little cod longlining in the Gulf of St. Lawrence. None of them found any fishing by the fleets they studied off Labrador or the northeast coast of Newfoundland, except that Rathbun ( 1887) made some mention of the New Englanders’ final efforts in the shore fisheries there. Likewise, the minor banks of the central Scotian Shelf, from Misaine Bank to Sambro Bank, have never been reported as important cod grounds, nor has there been much longlining near the Nose of Grand Bank. Thus, at all three times the gross distribution of the cod longlining grounds exploited by these various fleets was strikingly similar. In some areas, however, there have been local differences in the grounds. Most of these can be explained as the consequences of human decisions and thus cannot be taken as evidence for underlying biological change. Flemish Cap, for example, was being explored by the New England fleet in the time of Rathbun (1887) but was not fished for cod with longlines in 1990. McKenzie ( 1942) unfortunately did not make clear whether the Canadian fleet fished there in the 1930s but for the 1950s and 1960s when the Portuguese dory schooner fleet and Norwegian longliners were active in the Grand Banks cod fisheries, the ICNAF Statistical Bulletins show only negligible hook-and-line effort on the Cap. The cod there are probably too small to justify an offshore longline fishery, and it seems unlikely that the exploratory New England fishery was continued once the true potential of the ground became known. Similarly, the apparent southward retreat of the cod grounds on Grand Bank is probably an artifact. The northern-most area fished by the New England schooners in the 1880s is now part of NAFO Division 3L. In 1990, the longline fleet had very limited cod quotas for that area, which they could take without going far into the Division, while a concentration of gillnetting around the Virgin Rocks (46”25’N) dissuaded the longline captains from going that far north (Kenchington and Halliday, 1994). Meanwhile, the modern fishery expended some small amount of effort on Green Bank (which was also fished in the 1930s) and on the grounds around Whale Deep and towards the Nose of Grand Bank, all of which areas Rathbun ( 1887) recorded as unfished and unexplored. This may be no more than an expansion of activity onto marginal grounds. Georges Bank has also seen an expansion of longline effort, though for different reasons. It has been fished for cod since the 183Os, but as late as the 1880s this was still exclusively a handline fishery (Goode, 1887; Rathbun, 1887). Cod longline gear began to be used on Georges at some point in the first half of the twentieth century, perhaps with the adoption of fully powered boats that could cope with the strong tides. By the 1960s Canadian fishermen were longlining on this Bank on much the same ground (Halliday et al., 1986) as they exploited in 1990. The preceding changes in the area fished cannot be taken as evidence of any biological instability. For the area from St. Pierre Bank to Sable Island Bank, however, the available descriptions of fishing grounds do suggest possible changes in cod distributions, albeit on an inter-annual rather than multi-decadal time scale. St. Pierre Bank had been an important ground for the early cod longline fishery, but was abandoned in the late 1870s. There was some renewal of interest by the New Englanders in 1883 and 1884. In the late 1930s. the next period for which data are available, it was the single most important bank for Canadian fresh cod
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fishing, accounting for nearly 30% of the catch. It was still being fished by Scotia-Fundy Region longliners in 1990, although its relative importance had greatly declined. On the Scotian Shelf, Banquereau seems to have once been an important cod ground although the state of the fishery there in the 1880s is unclear-Goode ( 1887) claimed that it was “extensively resorted to” for cod, and the text of Rathbun ( 1887) agreed. However, his chart of this bank bore the legend “Not much fished on at present by Americans”, and his appendix supported that position. Perhaps the cod fishery on Banquereau had died away between 1880 and 1885. By 1940, however, this bank was second in importance only to St. Pierre Bank for the Canadian fresh cod fishery, and was sometimes exploited by the saltfish schooners also. It was still important to cod longliners in the mid-1980s (Sinclair, 1992; Kenchington and Halliday, 1994)) but was of lesser interest to the fleet by 1990. Likewise, Rathbun ( 1887) noted that the Sable Island area (then known as ‘Western Bank’ and incorporating the modern Middle, Sable Island, Western and Emerald banks) was one of the most important grounds in the northwest Atlantic for the New England fleet of the 1880s. The winter cod fishery was particularly concentrated on Emerald and Western banks, but in the spring and early summer the fishing moved eastward to the vicinity of Sable Island itself (near the eastern end of the bank to which it has given its name). These four banks were still important to the Canadian fresh-cod fleet in the 1930s the combined catch from the whole area being some 35% of the total, and McKenzie (1942) noted the same seasonal movement of the fleet as Rathbun ( 1887) had. The salt-fish schooners also exploited Western Bank regularly, making their first trip of each season there before heading to Grand Bank for the summer. During the following four decades, this area seems to have declined in importance, although as late as 1984-85 the analysis by Sinclair ( 1992) of logbook data showed some scattered longlining for cod across Sable Island Bank. By 1990, Sable Island and Middle banks had been all but abandoned by the cod longline fleet. The former was reported to yield little but skate (Ruju spp.) . Even on Western and Emerald banks cod was by then only a bycatch of the haddock fishery (Kenchington and Halliday, 1994). In the opinions of many longline captains, these changes in the grounds resulted from a severe decrease in cod availability which they believed was the result of local, intense trawling during the 1980s (Kenchington and Halliday, 1994). While that remains a plausible hypothesis, the variable availability of cod across Banquereau and St. Pierre Bank that is suggested by the report of Rathbun ( 1887)) and which is unlikely to have been caused by the low fishing efforts of the time, suggests that the cod may not be consistently productive on these banks. There is no obvious environmental cause of reduced stability in this area. In the last half century, water temperature and salinity variations on Banquereau have been similar to, but weaker than, those on the western Scotian Shelf (Petrie and Drinkwater, 1993). St. Pierre Bank and Banquereau do, however, receive migratory cod from the Gulf of St. Lawrence in winter, although the extent of this migration varies from year to year (Moguedet, 1991; Hanson and Nielsen, 1992). Moreover, on St. Pierre Bank cod have recently shown an apparent movement to great depths, beyond the range of the longline grounds (Moguedet, 1991). It is possible that inter-annual variations in migratory patterns or depth distributions, rather than in productivity per se, led to the variations in cod availability that Rathbun (1887) observed.
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The offshore Scotian Shelf banks further to the westward have not shown this variability. However, Roseway Bank, which lies closer to the land, has seen a marked decline in longlining in recent years. It was fished in the 1880s (although more by Nova Scotian than New England boats), as indeed it was in the 1930s and as late as 1985 (Halliday and Sinclair, 1987). This activity had all but ceased by 1990 (Kenchington et al., 1994), most likely because local catch rates had been depressed by intensive fishing-apparently a common problem on the Nova Scotian inshore grounds (Kenchington and Halliday, 1994). Thus, with the possible exceptions of the St. Pierre Bank-Sable Island area and Roseway Bank, the cod longline grounds have shown general stability over the past century, with local changes driven by purely human factors. On a few exceptional banks there do seem to have been changes in cod abundance, which may simply be the result of intense local fishing effort but which may alternatively have been driven by changes in underlying biological productivity. 3.2. Haddock grounds The long-term trend in haddock longlining grounds is radically different from that seen in the cod grounds and does show a profound change in resource productivity over a multidecadal time scale. In the 1880s the New England haddock fishery was confined to the area from LaHave Bank westwards, presumably being constrained by the need to land these fish fresh in Massachusetts ports. These haddock seem to have mostly been caught in winter, particularly on Browns Bank, and may have been exploited more by handlining than by longlining (Goode, 1887; Rathbun, 1887). Over the following half-century, Canada developed a major haddock fishery. By the late 193Os, about half of these fish were taken from coastal waters, particularly in the Bay of Fundy but also in Sydney Bight and elsewhere along the shore. These haddock were mostly taken by longlining from small boats, but there was also a significant trap fishery and, in some areas, the dory schooners worked close to the land. Offshore, meanwhile, over two thousand tons per year were caught on St. Pierre Bank by the schooners, nearly as much was taken from Western Bank (largely by trawlers), and lesser amounts were caught on each of the other offshore Scotian Shelf banks. In addition, there were small, if geographically extensive, haddock fisheries on Grand Bank and in the Gulf of St. Lawrence. The fish in the latter area were seasonal migrants which withdrew from the Gulf for the winter. In this period United States’ boats fished off Canada for haddock, primarily from Browns to LaHave banks, much as in the time of Rathbun ( 1887)) although they also worked other grounds from the Bay of Fundy to St. Pierre Bank (McKenzie, 1946a) and they presumably fished off their own shores too. Much of their haddock catch in the 1930s was taken by trawling. The map of haddock grounds, presented by Needler ( 193 1)) which did not distinguish longlining areas from trawling ones, nor the grounds preferred by Canadian and United States’ captains, shows that these fisheries already worked essentially the same grounds in 19 18-25 as they did in the late 1930s plus others further to the westward which McKenzie (1946a) did not consider. St. Pierre Bank had not, however, developed the relative importance in the early 1920s that it achieved 15 years later.
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By 1990, the haddock longline fishery had essentially contracted to the Scotian Shelf and, except for minor bycatches, to areas from Western Bank westwards, including inshore waters. The fishery had not only withdrawn from St. Pierre Bank (average landing in 198791 by all hook-and-line gears, 77 tons: Halliday and Clark, 1995), but also from the Gulf of St. Lawrence (average landing 1 ton), Sydney Bight (average landing 98 tons) and, to a large extent, from the Bay of Fundy (separate catch data not available). In the western offshore areas haddock production has been more persistent, and by 1990 this species was often the predominant catch of the groundfish longliners, in terms of value if not of volume. All of the western banks were, of course, fished by Canadians, the former United States fishery having been displaced by the extension of jurisdiction in 1977. In most cases, the areas fished on these banks do not seem to have changed between 1940 and 1990 (Fig. 3 and Fig. 4). However, while the famed Browns Bank winter haddock fishery (Rathbun, 1887; McKenzie, 1946a) continued into the 1980s (Halliday and Sinclair, 1987)) late in that decade the shoal water of the bank was abandoned and the fleet moved into the deeper gully between the bank and the land (Kenchington et al., 1994). There has also been an equivalent reduction in haddock longlining on Roseway Bank to that noted above for cod. Many longline captains believe that intensive trawling has caused these local changes by depleting the haddock resources and modifying bottom habitats (Kenchington and Halliday, 1994). The reasons for the major contraction in the exploitable range of haddock are not fully known. After the interviews of McKenzie (1946a) but before the northern grounds were abandoned, a trawl fishery actually expanded on Grand Bank and achieved its peak catches in 1955. Hodder (1966) and Templeman et al. (1978) have shown that the subsequent contraction from St. Pierre and Grand banks resulted, in part, from a long period of generally poor recruitment after 1956, probably as a result of adverse environmental conditions. There was a prolonged cooling trend in these waters from the early 1950s to the late 1960s (Petrie and Drinkwater, 1993). These grounds were certainly at the northern and eastern limits for this species, where the haddock might be expected to be vulnerable to cooling. Intensive fishing on the declining resource no doubt played a part too, particularly in retarding the recovery of the haddock during the warming trend of the 1970s (Petrie and Drinkwater, 1993). Whether such an explanation can also account for the disappearance of haddock from the Gulf of St. Lawrence and the Bay of Fundy is unknown. 3.3. Halibut grounds The New England fishermen discovered the deepwater halibut grounds (which can be at depths of 500 fathoms or more: Kenchington et al., 1994) in the 187Os,having previously fished this species both on the continental shelf as far east as Grand Bank and in inshore waters (Rathbun, 1887). They explored the continental slope, heading gradually eastward as they fished down each patch in turn. By the early 1880s they were fishing the slope from the edge of Georges Bank all the way to the Tail of Grand Bank and up its southeastern side to about 44’N, as well as the edges of the Northeast Channel (between Georges and Browns banks) and the Laurentian Channel (between St. Pierre Bank and Banquereau). These deepwater grounds have remained unchanged over the past century, except that they now extend all the way to Flemish Cap, presumably as a result of further exploration.
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Moreover, the continental slope along the southern edge of St. Pierre Bank and the southwestern edges of Green and Grand banks, which Rathbun ( 1887) noted as the most important area for this species, was almost the sole ground for the small Canadian deepwater halibut fishery of the late 1930s (McKenzie, 1946b) and was still identified as a prime area by the halibut longline fishermen of 1990 (Kenchington and Halliday, 1994). In his one original contribution of present relevance, Close (no date) noted the importance of the edges of Green Bank and of Banquereau for halibut in 1928. Besides this deepwater fishing by New England schooners, Rathbun ( 1887) made passing mention of an inshore fishery for halibut by small Nova Scotian boats. This continued into the 1930s and thence to the 1990s (McKenzie, 1946b; Kenchington et al., 1994). Thus, although the halibut was an almost unknown, virgin resource shortly before the time of Rathbun (1887), there has been remarkable stability in the grounds fished for it during the last century. There is certainly no evidence here of any distributional change in the northwest Atlantic halibut resource. 3.4. Hake and tusk grounds Rathbun ( 1887) mentioned that some white hake were taken on the deepwater halibut grounds off LaHave and Emerald banks. This continued in 1990, with the halibut longliners taking hake both as halibut bait and for landing (Kenchington and Halliday, 1994). Rathbun (1887) also reported that hake, tusk and pollock (Pollachius h-ens) were caught on Roseway Bank, although mostly by Nova Scotian vessels rather than New Englanders. The latter did fish hake and pollock on Browns. The general reduction in effort on Roseway Bank, noted above for cod, has affected this fishing for hake and tusk also, while they were at most a bycatch on Browns by 1990. Meanwhile, pollock have become no more than a minor bycatch of the longline fisheries, being pursued with gillnets instead (Kenchington and Halliday, 1994). Finally, Rathbun ( 1887) noted a small hake fishery in the Bay of Fundy, where local boats caught these fish in an area aptly known as ‘The Mud’. During the following century, this fishery expanded across the mouth of the Bay and, in 1990, it was the only significant longline activity in that area. A second hake fishery on muddy bottom also arose on the central Scotian Shelf. The growth of these specialized hake fisheries was presumably driven by market changes, and there is no reason to suppose that it was linked to any change in the abundance of the resource.
4. Discussion This comparison of the longline grounds fished over the past century suggests that the halibut grounds have been essentially stable since they were first discovered, and that the cod longline grounds appear to have been equally stable in their gross features although there have been more local changes which may not all be explicable as the simple consequences of human decisions. The haddock grounds have seen similar local changes but also a major contraction from eastern and northern areas. What little is known of the hake and tusk grounds is insufficient to support any conclusions about their long-term stability.
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It remains possible that the absence of more fundamental changes in the cod grounds is an artifact of the available data. Firstly, the cited sources all imply that the Gulf of St. Lawrence grounds have been of little significance to the longline fisheries. It might have been otherwise had Rathbun ( 1887) included the grounds fished by Canadians in his descriptions, had McKenzie ( 1942) considered the activity of the inshore fleet, or had Kenchington et al. ( 1994) mapped the areas exploited by boats based in Canada’s Gulf Region. That fleet landed an average of 11700 tons of hook-caught cod per year in 198791, virtually all of it being taken in the Gulf of St. Lawrence, whereas under 300 tons of the 32 500 landed by Scotia-Fundy Region hook-and-line boats came from those waters (Halliday and Clark, 1995). The distinction resulted from management regulations which largely prevented inter-Regional movements by these fleets (Parsons, 1993; Kenchington and Halliday, 1994). The development of this local longlining in the Gulf over the past century and more has most probably been the result of technological diffusion, rather than any change in cod distributions. A second, and perhaps more dramatic, change in the grounds fished has been concealed by the chance dates of the three principal studies cited here. Grand Bank was the major source of cod for the New England fleet in 1880 (Rathbun, 1887). By 1940, it was the principal source of cod for the Canadian salt fishery, although the bulk of the national catch was landed fresh and was not caught so far to the eastward (McKenzie, 1942). Thereafter, the offshore salt fishery declined and, had the survey of Kenchington and Halliday ( 1994) been carried out in 1970 or 1980, it would have found no Nova Scotian cod longlining on Grand Bank at all. In the mid-1980s, however, the offshore salt-fish industry re-appeared (although the catch is now returned fresh and salted ashore) and with it the fishery on Grand Bank. This renewed fishery was specifically targeted on the very large cod traditionally available in that area, which size of fish is required for efficient salting, as it probably also is for the profitable operation of the large longline boats necessary when fishing the Grand Banks (Kenchington and Halliday, 1994). These very large fish may have been scarce on Grand Bank in the wake of the intense trawl fishing of the early 1970s. Only with the reduction in effort that following the extension of Canadian jurisdiction in 1977 may sufficient fish have survived to reach these large sizes, and hence to make this type of fishing profitable again. If this is indeed the reason for the abandonment of, and return to, the Grand Bank grounds, it implies an expected response of the stock to extreme fishing pressure rather than any change in the underlying biological productivity. Lastly, and perhaps more seriously, the lack of a comprehensive description of inshore fishing grounds before modern times prevents any discussion of changes in those areas in earlier decades. This is unfortunate, since one of the few significant reported changes in the longline grounds in recent years has been a general withdrawal from coastal waters (Kenchington and Halliday, 1994; Kenchington et al., 1994). The general decline in fishing on Roseway Bank, which has been noted above but which is also clear in a comparison of maps of longline effort in 1960-72 (Halliday et al., 1986) with those of Halliday and Sinclair (1987) for 1982-84 and Kenchington et al. ( 1994) for 1990, may represent part of this trend; Roseway is the only near-shore bank on the Scotian Shelf which was consistently fished by the fleets whose grounds were recorded in the 1880s and 1930s. Assuming that the decline in inshore fish is real, it is not known whether it results from severe depletion of inshore stock components or simply a range contraction by a homogeneous resource
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which has drawn the fish onto preferable, offshore grounds. The latter would not violate the assumption of stable potential productivity in the assessed stock units, though the former might, while both imply a real loss of inshore productivity. In conclusion, despite the enormous increase in fishing effort on the groundfish resources of the northwest Atlantic in the past hundred years, the areas preferred for fishing with longlines in 1990 were much the same as they had been in 1880 and 1940. The present analysis has detected the known contraction in the range of haddock, while providing a reminder that it affected the Gulf of St. Lawrence and the Bay of Fundy as well as St. Pierre and Grand banks. It has also indicated a possible pattern of inter-annual variability in cod productivity on the eastern Scotian Shelf and St. Pierre Bank which may merit further investigation. Otherwise, all of the changes in the cod and haddock grounds can readily be explained as the direct effects of heavy fishing pressure on recruited year classes or of human and technical factors. The halibut grounds do not appear to have responded even to these. This comparison of fishing grounds over the past century has therefore failed to reject the common assumption of underlying stability in resource productivity, as it applies to northwest Atlantic cod and halibut, although this assumption is clearly untenable for haddock near the margin of their natural range. This apparent stability in cod and halibut productivity has been maintained in waters that are known to have the highest inter-annual variability in sea-surface temperature of any area in the temperate and tropical Atlantic (Weare, 1977). This degree of variability is seen in several data sets, and appears to be driven by changes in the strength of the Labrador Current (Petrie and Drinkwater, 1993). Since the common assumption of stable potential productivity, which underlies most stock assessments, appears generally realistic in this highly variable region, it may therefore be accepted in other sea areas provided that the species in question is not living near the limits of its natural range.
Acknowledgements I once again thank the many fishermen who provided information on their fishing grounds during our interview survey, and the various members of the Department of Fisheries and Oceans staff who have assisted with the interpretation of those data, particularly Glen Harrison, Mark Showell, Alan Sinclair, Dr. Ken Frank and Ken Drinkwater. My text was greatly improved by the comments of an anonymous referee. Finally, and most particularly, I am indebted to Dr. Ralph Halliday for initiating our survey and for his guidance throughout the work. This paper was initially prepared while the senior author was on an FAO/UNDP mission to the Marine Fisheries and Technology Station at Cox’s Bazar, Bangladesh.
References Balcom, B.A., 1977. History of the Lunenburg Fishing Industry. Lunenburg Marine Museum Society and Nova Scotia Museum, Lunenburg, 71 pp. Balcom, B.A., 1984. The Cod Fishery of Isle Royale, 1713-58. Studies in Archaeology, Architecture and History, Parks Canada, Ottawa, 88 pp.
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Close, A., no date. The North Atlantic and Gulf of St. Lawrence Fishing Grounds. Privately published, London, 28 pp + chart. Cushing, D.H., 1982. Climate and Fisheries. Academic Press, London, 373 pp. De Loture, R., 1957. History of the great fishery of Newfoundland. US Fish Wildlife Serv., Spec. Sci. Rep. Fish., 213: 147. Goode, G.B., 1887. The Fisheries and Fishery Industries of the United States. Section V. History and Methods of the Fisheries. Government Printing Office, Washington, DC, Vol. 1,808 pp. Halliday, R.G. and Clark, K.J., 1995. The Scotia-Fundy Region groundfish hook and line fisheries: A digest of quantities and sizes landed, and comparisons with other gear types. Can. Manuscr. Rep. Fish. Aquat. Sci., 2271: 178. Hahiday, R.G. and Sinclair, A.F., 1987. Fishing grounds of groundfish longliners from the Cape Sable Island area, southwestern Nova Scotia, in 1982-84. NAFO Sci. Count. Stud., 11: 75-80. Halliday, R.G., McGlade, J., Mohn, R., O’Boyle, R.N. and Sinclair, M., 1986. Resource and fishery distributions in the Gulf of Maine area in relation to the Subarea415 boundary. NAFO Sci. Count. Stud., 10: 67-92. Hanson, J.M. and Nielsen, G.A., 1992. Catches of 4T-Vn (Jan.-Apr.) cod in the 4Vs winter fishery, 1980-1992. Canadian Atlantic Fisheries Scientific Advisory Committee, Research Document 92/5 1. Hodder, V.M., 1966. Trends in the haddock fishery of ICNAF Subarea 3. ICNAF Res. Bull., 3: 55-63. Kenchington, T.J. and Halliday, R.G., 1994. A survey of fishing practices in the Scotia-Fundy Region groundfish longline fisheries. Can. Manuscr. Rep. Fish. Aquat. Sci., 2225: 642. Kenchington, T.J., Hahiday, R.G. and Harrison, G.D., 1994. Fishing grounds exploited in 1990 by groundfish longliners based in Canada’s Scotia-Fundy Region. NAFO Sci. Count. Stud., 20: 65-84. McKenzie, R.A., 1942. Canadian Atlantic offshore cod fishery east of Halifax. Bull. Fish. Res. Board Can., 61: 13. McKenzie, R.A., 1946a. The haddock fishery of grounds fished by Canadians. Bull. Fish. Res. Board Can., 69: 30. McKenzie, R.A., 1946b. The Canadian Atlantic halibut fishery. Bull. Fish. Res. Board Can., 71: 29. Moguedet, P., 1991. Variation in cod stock abundance in NAFO Subdivision 3Ps in the period 1978-1990. NAFO SCR Dot. 9 1/ 114, Serial No. N2007. Needler, A.B., 1931. The haddock. Bull. Fish. Res. Board Can., 25: 28. Parsons, L.S., 1993 Management of marine fisheries in Canada. Can. Bull. Fish. Aquat. Sci., 225: 763. Perley, M.H., 1852. Reports on the Sea and River Fisheries of New Brunswick. Queens Printer, Fredericton, 294 PP. Petrie, B. and Drinkwater, K., 1993. Temperature and salinity variability on the Scotian Shelf and in the Gulf of Maine 1945-1990. J. Geophys. Res., 98: 20079-20089. Rathbun, R., 1887. The Fisheries and Fishery Industries of the United States. Section III. The Fishing Grounds of North America. Government Printing Office, Washington, DC, xviii + 177 + xxxii pp. Sinclair, A.F., 1992. Fish distribution and partial recruitment: The case of the eastern Scotian Shelf cod. J. Northwest Atl. Fish. Sci., 13: 15-24. Templeman, W., Hodder, V.M. and Wells, R., 1978. Age, growth, year-class strength, and mortality of the haddock, Melanogrammus aeglejnus, on the southern Grand Bank and their relation to the haddock fishery of this area. ICNAFRes. Bull., 13: 31-52. Weare., B.C., 1977. Empirical orthogonal analysis of Atlantic Ocean surface temperatures. Q. J. R. Met. Sot., 103: 467-478.
Fisheries Research 25 (1996) 139-154
Long-term stability and change in the commercial groundfish longline fishing grounds of the northwest Atlantic T.J. Kenchington Gadus Associates, R.R. #I. Musquodoboit Harbour, N.S., BOJZW, Canada
Abstract The fishing grounds in the northwest Atlantic Ocean that were exploited by commercial groundfish longline boats in the 188Os, in about 1940 and in 1990 are compared and examined for evidence of changes in fish distributions over multi-decadal time scales. In general, the grounds fished were notably similar at the three times, the halibut grounds being particularly stable. Moreover, most of the changes detected can be attributed to developments in markets, regulations or similar human concerns. However, the known withdrawal of haddock from the former limits of its range is seen as a change in the areas fished for that species. There is also some evidence for shorter-term changes in cod abundance on grounds near the entrance to the Gulf of St. Lawrence. It is suggested that the general stability in the grounds fished is consistent with the potential productivity of the resources having also remained stable, despite the great increase in fishing effort during the last century. The common assumption of stability in productivity that is implicit in most stock assessments is therefore supported, except for those stocks that are near the limits of their species’ range. Ke.vwords: Fishing grounds; Historical development; Longline; Northwest Atlantic;
Productivity
1. Introduction
Fisheries stock assessment necessarily involves some prediction of a resource’s future response to fishing effort. Like all predictions, these are extrapolations from past conditions. In most cases, they rely on an assumption of continuing underlying stability, not in fish production but in potential productivity in the absence of fishing effort. Such an assumption is almost impossible to test. Given the importance of this stability assumption and the lack of adequate tests, even uncertain indications of long-term stability in resource populations, or of the absence of such stability, are of considerable interest. One potential indicator is fish distribution. 0165-7836/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved SSDlO165-7836(95)00414-9
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Stability in distribution need not indicate stability in productivity, but marked distributional change certainly suggests the local absence of that stability. Thus, studies of distribution cannot confirm, but may serve to falsify, the stability assumption. Appropriate scientific data on the distributions of marine resources, based on regular research vessel surveys, have only been collected for a few decades. To judge the degree of stability in productivity over multi-decadal time scales, it is necessary to resort to studies of the distribution, not of the fish themselves, but of the commercial fishing grounds. Where appropriate data are available, such as with the Scanian herring fishery, such studies have reached back for several centuries with considerable success (Cushing, 1982). The locations of commercial fishing grounds are controlled by many factors, but these can usefully be grouped into three classes: biological factors, the interactions between the fish and the fishing gear, and human/technical factors. Commercial fishing can only be carried out in places where fish of appropriate types and sizes are sufficiently concentrated. Hence, the locations of the grounds are partly determined by the distributions of the resources, which are themselves controlled by biological factors. It is not, however, sufficient for the fish to be present in an area. They must be available to the types of fishing gear used if that area is to be fished. The characteristics of the gear and their interactions with the behaviour of the fish will therefore partly determine the locations of the grounds, while the environment may influence these interactions (some gadoids will not take baited hooks set on a muddy bottom, for example: Kenchington and Halliday, 1994). Finally, some grounds which could be fished will not be because they are too distant from landing ports, too exposed to bad weather or subject to some other technical or human constraint that has no direct connection to resource biology. Of these three classes, the biological factors concern the distribution of the fish and hence are the information desired when examining long-term resource stability. The technical factors are matters of human decisions which may be recorded, interpreted and understood with relative ease. The interactions between fish behaviour, fishing gear and the environment are, however, both complex and, in almost all cases, unknown. It is therefore impossible to judge the stability or otherwise of the distribution of a fish stock by comparing, for example, the grounds exploited by longlining in some earlier period with those now fished by otter trawling, even were the same species and sizes of fish targeted in each case. Thus, the radical changes in fishing methods during the twentieth century usually prevent useful comparisons between modern fishing grounds and those of earlier eras. Conclusions about the stability of the resources under intense modern fishing pressures cannot often be built on distributional studies. In the northwest Atlantic groundfish fisheries, however, many fishermen still use longline gear ’ that is unchanged in its fundamentals from that employed by dory schooner fishermen in the second half of the nineteenth century. The types of boats from which this gear is set have changed completely in the last hundred years and there have been other developments, in fish marketing for example, which have affected fishermen’s behaviour. However, the only technological changes relevant to the interactions between the fish and the gear have ’ The type of demersal hook-and-line fishing that is generally known as ‘longlining’ is commonly referred to as ‘trawling’ by Atlantic Canadian and New England fishermen, who term otter trawling ‘dragging’. They also call longline snoods ‘gangions’. In this paper, I use the internationally recognized terms, converting as necessary from the terminology of cited sources, while 1 modernize all place names.
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been: the adoption of circle hooks and other modern hook designs, some minor changes in the relative frequencies of different bait types, a shortening of the typical lengths of the snoods, and the general adoption of synthetic materials (Kenchington and Halliday, 1994). None of these changes seems likely to have affected the catching process sufficiently to have altered the distribution of the fishing grounds. Indeed, for over a century the longline fishermen have maintained their preference for only five principal target species: Atlantic cod (Gadus morhua) , haddock (Melanogrammus aeglejks) , Atlantic halibut (Hippoglossus hippoglossus) and, to a lesser extent, white hake (Urophycis tenuis) and tusk (Brosme brosme: Rathbun, 1887; McKenzie, 1942; McKenzie, 1946a; McKenzie, 1946b; Kenchington and Halliday, 1994; Halliday and Clark, 1995). Their mode of fishing, and hence the relationship between their chosen grounds and the distribution of the fish, seems likely to have been equally constant. Kenchington et al. (1994) and Kenchington and Halliday ( 1994) have presented maps of the grounds fished by Nova Scotian groundfish longliners in 1990, based on data gathered through extensive interviews of fishing captains. They have also reviewed comparable published accounts (based on interview or logbook data) concerning grounds fished in the past three decades (Halliday et al., 1986; Halliday and Sinclair, 1987; Sinclair, 1992). Since completion of their work, however, some earlier sources of information have come to light. In particular, Rathbun ( 1887) published a detailed, and partially illustrated, account of the grounds fished by the New England schooner fleet in about 1880, while McKenzie (1942), McKenzie ( 1946a) and McKenzie ( 1946b) presented some information on the location of fishing by both Canadian and New England vessels in 1938-40. With these additional sources, it is now possible to judge the stability of groundfish longline fishing grounds in the Canadian portion of the northwest Atlantic (Fig. I ) from 1880 to 1940 and thence to 1990. It is fortunate that this comparison should be possible since this particular area is notable for its high degree of inter-annual environmental variation (Weare, 1977; Petrie and Drinkwater, 1993). If the assumption of constant resource potential productivity is an acceptable approximation in the waters from Cape Cod to Grand Bank, it seems likely to be adequate in routine stock assessment calculations in many other sea areas. In this paper, the information from Rathbun ( 1887), McKenzie ( 1942), McKenzie (1946a), McKenzie (1946b), Kenchington et al. (1994) and other relevant sources is evaluated. The grounds fished at various times are then examined for evidence ofthe changes in distributions that would refute the assumption of stable potential productivity. The grounds themselves are not described here since that information is available in the cited sources.
2. The available data 2.1. Fishing grounds exploited by New England schooner$shermen
in about 1880
As part of G.B. Goode’s monumental survey of the fisheries of the United States, Rathbun ( 1887) compiled information on the locations of the fishing grounds. His account contains information from as late as 1885, but it also contains remarks on some areas fished in the
T.J. Kenchington / Fisheries Research 25 (1996) 139-154
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50”
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Fig. 1. Map of the northwest Atlantic showing place names used in the text. The Scotian Shelf grounds (banks) indicated by numbers are: 1, Misaine; 2, Middle; 3, Western; 4, Emerald; 5, Sambro; 6, LaHave; 7, Roseway. ‘C.B.I.’ indicates Cape Breton Island (a part of Nova Scotia). The bathymetric contours shown are for 100 and 200 m depth.
1850s. For the New England fisheries his data were gathered from various sources, but particularly from the personal experience and knowledge of Capt. J.W. Collins, who served as a form of technical advisor to Goode. The reliability of Collins’ reports cannot be confirmed but there is little reason to doubt their major features. Rathbun ( 1887) presented his information in a verbal format, supplemented by charts for selected areas only. The latter are summarized in Fig. 2. Since the comparative data from later periods are exclusively from waters off Canada, only information of Rathbun ( 1887) on grounds in that area is used here. With the exception of part of the Bay of Fundy, all such grounds are a considerable distance from United States’ ports. Hence these data are almost exclusively from the offshore schooner fishery, although Rathbun ( 1887) did provide some information on inshore fishing by Nova Scotians. In the 188Os, New England schooner fishermen made some trips to West Greenland and even a few to the Iceland grounds. These distant grounds are not considered further in this paper. By 1880, there had been cod fisheries in the northwest Atlantic for about 400 years. For most of that time, however, the fish had been caught by handlining, usually from small boats based at shore stations. There had been only a limited amount of offshore fishing, which was carried out by handlining from fishing ships and schooners (Balcom, 1977; Balcom, 1984). The French introduced longline techniques to the Grand Banks cod fisheries in about 1789, but their activity ceased with the outbreak of war 4 years later (De Loture, 1957). It was not until the early 1840s that their resumed longlining came to the attention
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143
50"
0 45”
40”
“_,IC.’
[.,&! . ..I 70”
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Fig. 2. Map showing some of the grounds
I 60”
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fished in about 1880 by New England longline fishermen, re-drawn
fromthe chartspreparedby Rathbun ( 1887). The crosses indicatesomespecific locations where particularly good halibut catches were taken in the late 1870s or early 1880s. Rathbun’s disagreed with his text.
charts were incomplete
and in places
of local fishermen (Perley, 1852; Goode, 1887) when, in an independent development, some inshore fishermen of Massachusetts began to set halibut longlines. Over the next few years longline gear was adopted by many New Englanders for both cod and halibut (Goode, 1887). By the end of the 184Os, many fishermen in what is now Canada had also taken up the new gear (Perley, 1852). As longlining became accepted, the New England offshore schooner fishery also adopted dory fishing, in which the lines were worked from small boats ( ‘dories’), with the schooner acting as a mother ship. With this further technological change, the cod fishermen began to exploit the offshore banks to a much greater extent than had previously been possible, resulting in a major change in the grounds commonly fished (Goode, 1887; Rathbun, 1887). By 1880, therefore, the offshore dory longline fishery for cod had been established for over 20 years; sufficient time for the better grounds to be discovered and, given the preceding four centuries of related development, for the fishery to achieve a quasi-stable state. While some areas had yet to be fully explored (Rathbun, 1887)) in general the grounds fished for this species in about 1880 should have been those optimal for the fishery of the time, and no major differences in the cod grounds between 1880 and 1990 should have resulted from the nineteenth-century fishermen lacking knowledge of their fish. In contrast, the New England offshore fishery for halibut only began in the 186Os, and the prolific deepwater grounds along the continental slope were not discovered until the 1870s. It is clear from the account of Rathbun (1887) that in 1880 this fishery was still in
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a ‘fishing-up’ phase: the fleet moving on as the available biomass on each newly discovered ground dropped from virgin levels. In consequence, both the biology of the halibut resource and human knowledge of its distribution were in a state of flux in 1880. The grounds fished at that time need not, therefore, be directly comparable with those of later decades. Only a few grounds were fished for haddock, hake or tusk by the New England fleet in the 1880s. The fisheries for these species seem to have been limited by restricted markets and the difficulty of preserving these fish during a long voyage to the port of landing; unlike cod, they do not salt well. Thus, the data of Rathbun (1887) on these grounds are of restricted value for present purposes. 2.2. Fishing grounds exploited by the Canadian offshorejshery
in the late 1930s
Half a century after the work of Rathbun ( 1887)) McKenzie (McKenzie, 1942; McKenzie, 1946a; McKenzie, 1946b) published some information on the grounds fished by the few trawlers and the considerable fleet of offshore schooners which then operated from Canadian ports *. His data were largely drawn from interviews with fishing captains conducted from 1938 to 1940. While he largely confined his attention to Canadian offshore boats, McKenzie also provided some information on the local inshore fisheries and on United States’ fishing in waters off the Canadian coast. Unfortunately, he presented most of his distributional data by statistical unit areas, which give only a crude, and sometimes misleading, indication of the actual grounds fished. He did provide one more precise map showing the principal offshore grounds for haddock, and this is re-drawn here as Fig. 3. By the late 1930s the New England offshore groundfish fisheries had largely converted from longlining to trawling. The Canadian fishery, in contrast, still relied on dory fishing from schooners for all of its salt cod, for the great majority of its fresh cod and halibut caught offshore, and for more than half of the fresh haddock taken there. Many Canadian inshore boats were mechanized by the 1930s although they still relied on handlines and longlines for groundfish fishing. Except for the haddock fisheries, McKenzie did not clearly distinguish between the grounds fished by the fresh-fishing schooners and those worked by the steam trawlers. There were few of the latter, however (only three in 1938-39, although more in 1940)) and they appear to have concentrated on haddock (and perhaps other species not pursued by the schooners), so McKenzie’s (McKenzie, 1942; McKenzie, 1946b) descriptions of the cod and halibut grounds can be taken to represent those exploited by dory schooners. Some supplementary data are available for this same general period. Specifically, Needler ( 193 1) provided a brief summary and accompanying map of the haddock grounds fished in 1918-25, although she did not distinguish those fished with different gears. Later, Close (no date) published a chart of the northwest Atlantic fishing grounds and an accompanying booklet. Unfortunately, his work relied heavily on that of Rathbun ( 1887)) often quoting it verbatim and out of chronological context. Moreover, Close (no date) included information on the trawling grounds which is not of present relevance. However, he did record a few original observations on the halibut grounds fished in 1928 which are of value here. *Newfoundland was not then a pact of Canada. Thus, the ‘Canadian’ offshore fishery of the 1930s was almost exclusively based in Nova Scotian ports.
i? J. Kenchington / Fisheries Research 25 (1996) 139-154
145
50"
..
‘“L,_
“*;
!I
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40”
_,/:‘.-
I 70”
__<.fl’
I 65”
I 60”
I 55”
I 50”
I 45”
Fig. 3. Map showing the grounds most frequently fished by Canadian offshore haddock fishermen in 1938-1940, re-drawn from Fig. 3 of McKenzie ( 1946a). Some of the fishing on Western and Emerald banks was by otter trawlers, but otherwise the grounds shown were fished by dory schooners working longline gear.
2.3.
Fishing grounds exploited by Nova Scotian longliners in I990
Kenchington et al. ( 1994) published maps of the grounds fished by groundfish longliners with home ports in Canada’s Scotia-Fundy Region ’ using data derived from a survey of fishing captains. Their boats included small craft under 7 m in length and large offshore longliners of over 40 m. Most, however, were between 10 and 14 m long. Kenchington and Halliday (1994) have provided a full report on this survey, during which more than 300 fishermen were interviewed, including additional details on the grounds fished. The maps of Kenchington et al. (1994) of the grounds are summarized here as Fig. 4. Those maps did not distinguish between grounds fished lightly and those fished intensively, while the interviews provided only limited data on the seasons in which, and the species for which, particular grounds were fished. Otherwise the maps, and hence the present figure, are thought to have captured a reasonable record of the distribution of longline grounds fished by this fleet in 1990. These various sources together provide all that is known to science, with any certainty and detail, about the locations of longline grounds in the northwest Atlantic, None of them describes all such grounds, however. Moreover, as McKenzie (1946a) and Kenchington and Halliday ( 1994) make clear, fishermen from various ports and those with different ’ The coastline of the Scotia-Fundy Region extends from the northern tip of Cape Breton Island, along the Atlantic coast of Nova Scotia and around the Bay of Fundy to the international border with the United States.
T.J. Kenchington / Fisheries Research 25 (1996) 139-154
146
50”
j.‘. ..
r‘..
‘.
..:
45”
_ 7,_~;.-“.r.E
40” I
I
I
I
I
I
70”
65”
60”
55”
50”
45”
Fig. 4. Map showing the grounds fished during 1990 by groundfish longliners from Canada’s Scotia-Fundy Region, re-drawn from the figures presented by Kenchington et al. ( 1994).
sizes of boats usually choose rather different places to fish. Those selected by the fleets studied by Rathbun ( 1887), McKenzie ( 1942), McKenzie ( 1946a), McKenzie ( 1946b) and Kenchington et al. (1994) cannot, therefore, be fully comparable. No better evidence is available, however, and so a cautious comparison must be attempted.
3. A comparison of the grounds fished 3.1. Cod grounds In the early 1880s the late 1930s and again in 1990, the various cod longbne fleets considered here each fished a broad swathe from Georges Bank and the Bay of Fundy to Grand Bank, reaching north to about 48”N latitude in the 1880s although not quite so far in 1990. Grand Bank was the major cod ground for the New England schooner fleet in the 188Os, as it was for the Canadian salt-fish schooners of the 1930s and for the larger (over 20 m length) Scotia-Fundy Region longliners in 1990. The offshore banks of the Scotian Shelf were almost equal in importance to Grand Bank in the 188Os, they were the main centre for the Canadian fresh-cod fishery 50 years later, and were the principal grounds for the smaller Scotia-Fundy longliners of modern times. The more westerly banks seem to have been particularly consistently fished, although the Canadian schooner fleet of the 1930s largely left them to the New Englanders (Rathbun, 1887; McKenzie, 1942; Kenchington et al., 1994).
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Neither Rathbun ( 1887), McKenzie ( 1942) nor Kenchington et al. ( 1994) reported more than a little cod longlining in the Gulf of St. Lawrence. None of them found any fishing by the fleets they studied off Labrador or the northeast coast of Newfoundland, except that Rathbun ( 1887) made some mention of the New Englanders’ final efforts in the shore fisheries there. Likewise, the minor banks of the central Scotian Shelf, from Misaine Bank to Sambro Bank, have never been reported as important cod grounds, nor has there been much longlining near the Nose of Grand Bank. Thus, at all three times the gross distribution of the cod longlining grounds exploited by these various fleets was strikingly similar. In some areas, however, there have been local differences in the grounds. Most of these can be explained as the consequences of human decisions and thus cannot be taken as evidence for underlying biological change. Flemish Cap, for example, was being explored by the New England fleet in the time of Rathbun (1887) but was not fished for cod with longlines in 1990. McKenzie ( 1942) unfortunately did not make clear whether the Canadian fleet fished there in the 1930s but for the 1950s and 1960s when the Portuguese dory schooner fleet and Norwegian longliners were active in the Grand Banks cod fisheries, the ICNAF Statistical Bulletins show only negligible hook-and-line effort on the Cap. The cod there are probably too small to justify an offshore longline fishery, and it seems unlikely that the exploratory New England fishery was continued once the true potential of the ground became known. Similarly, the apparent southward retreat of the cod grounds on Grand Bank is probably an artifact. The northern-most area fished by the New England schooners in the 1880s is now part of NAFO Division 3L. In 1990, the longline fleet had very limited cod quotas for that area, which they could take without going far into the Division, while a concentration of gillnetting around the Virgin Rocks (46”25’N) dissuaded the longline captains from going that far north (Kenchington and Halliday, 1994). Meanwhile, the modern fishery expended some small amount of effort on Green Bank (which was also fished in the 1930s) and on the grounds around Whale Deep and towards the Nose of Grand Bank, all of which areas Rathbun ( 1887) recorded as unfished and unexplored. This may be no more than an expansion of activity onto marginal grounds. Georges Bank has also seen an expansion of longline effort, though for different reasons. It has been fished for cod since the 183Os, but as late as the 1880s this was still exclusively a handline fishery (Goode, 1887; Rathbun, 1887). Cod longline gear began to be used on Georges at some point in the first half of the twentieth century, perhaps with the adoption of fully powered boats that could cope with the strong tides. By the 1960s Canadian fishermen were longlining on this Bank on much the same ground (Halliday et al., 1986) as they exploited in 1990. The preceding changes in the area fished cannot be taken as evidence of any biological instability. For the area from St. Pierre Bank to Sable Island Bank, however, the available descriptions of fishing grounds do suggest possible changes in cod distributions, albeit on an inter-annual rather than multi-decadal time scale. St. Pierre Bank had been an important ground for the early cod longline fishery, but was abandoned in the late 1870s. There was some renewal of interest by the New Englanders in 1883 and 1884. In the late 1930s. the next period for which data are available, it was the single most important bank for Canadian fresh cod
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fishing, accounting for nearly 30% of the catch. It was still being fished by Scotia-Fundy Region longliners in 1990, although its relative importance had greatly declined. On the Scotian Shelf, Banquereau seems to have once been an important cod ground although the state of the fishery there in the 1880s is unclear-Goode ( 1887) claimed that it was “extensively resorted to” for cod, and the text of Rathbun ( 1887) agreed. However, his chart of this bank bore the legend “Not much fished on at present by Americans”, and his appendix supported that position. Perhaps the cod fishery on Banquereau had died away between 1880 and 1885. By 1940, however, this bank was second in importance only to St. Pierre Bank for the Canadian fresh cod fishery, and was sometimes exploited by the saltfish schooners also. It was still important to cod longliners in the mid-1980s (Sinclair, 1992; Kenchington and Halliday, 1994)) but was of lesser interest to the fleet by 1990. Likewise, Rathbun ( 1887) noted that the Sable Island area (then known as ‘Western Bank’ and incorporating the modern Middle, Sable Island, Western and Emerald banks) was one of the most important grounds in the northwest Atlantic for the New England fleet of the 1880s. The winter cod fishery was particularly concentrated on Emerald and Western banks, but in the spring and early summer the fishing moved eastward to the vicinity of Sable Island itself (near the eastern end of the bank to which it has given its name). These four banks were still important to the Canadian fresh-cod fleet in the 1930s the combined catch from the whole area being some 35% of the total, and McKenzie (1942) noted the same seasonal movement of the fleet as Rathbun ( 1887) had. The salt-fish schooners also exploited Western Bank regularly, making their first trip of each season there before heading to Grand Bank for the summer. During the following four decades, this area seems to have declined in importance, although as late as 1984-85 the analysis by Sinclair ( 1992) of logbook data showed some scattered longlining for cod across Sable Island Bank. By 1990, Sable Island and Middle banks had been all but abandoned by the cod longline fleet. The former was reported to yield little but skate (Ruju spp.) . Even on Western and Emerald banks cod was by then only a bycatch of the haddock fishery (Kenchington and Halliday, 1994). In the opinions of many longline captains, these changes in the grounds resulted from a severe decrease in cod availability which they believed was the result of local, intense trawling during the 1980s (Kenchington and Halliday, 1994). While that remains a plausible hypothesis, the variable availability of cod across Banquereau and St. Pierre Bank that is suggested by the report of Rathbun ( 1887)) and which is unlikely to have been caused by the low fishing efforts of the time, suggests that the cod may not be consistently productive on these banks. There is no obvious environmental cause of reduced stability in this area. In the last half century, water temperature and salinity variations on Banquereau have been similar to, but weaker than, those on the western Scotian Shelf (Petrie and Drinkwater, 1993). St. Pierre Bank and Banquereau do, however, receive migratory cod from the Gulf of St. Lawrence in winter, although the extent of this migration varies from year to year (Moguedet, 1991; Hanson and Nielsen, 1992). Moreover, on St. Pierre Bank cod have recently shown an apparent movement to great depths, beyond the range of the longline grounds (Moguedet, 1991). It is possible that inter-annual variations in migratory patterns or depth distributions, rather than in productivity per se, led to the variations in cod availability that Rathbun (1887) observed.
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The offshore Scotian Shelf banks further to the westward have not shown this variability. However, Roseway Bank, which lies closer to the land, has seen a marked decline in longlining in recent years. It was fished in the 1880s (although more by Nova Scotian than New England boats), as indeed it was in the 1930s and as late as 1985 (Halliday and Sinclair, 1987). This activity had all but ceased by 1990 (Kenchington et al., 1994), most likely because local catch rates had been depressed by intensive fishing-apparently a common problem on the Nova Scotian inshore grounds (Kenchington and Halliday, 1994). Thus, with the possible exceptions of the St. Pierre Bank-Sable Island area and Roseway Bank, the cod longline grounds have shown general stability over the past century, with local changes driven by purely human factors. On a few exceptional banks there do seem to have been changes in cod abundance, which may simply be the result of intense local fishing effort but which may alternatively have been driven by changes in underlying biological productivity. 3.2. Haddock grounds The long-term trend in haddock longlining grounds is radically different from that seen in the cod grounds and does show a profound change in resource productivity over a multidecadal time scale. In the 1880s the New England haddock fishery was confined to the area from LaHave Bank westwards, presumably being constrained by the need to land these fish fresh in Massachusetts ports. These haddock seem to have mostly been caught in winter, particularly on Browns Bank, and may have been exploited more by handlining than by longlining (Goode, 1887; Rathbun, 1887). Over the following half-century, Canada developed a major haddock fishery. By the late 193Os, about half of these fish were taken from coastal waters, particularly in the Bay of Fundy but also in Sydney Bight and elsewhere along the shore. These haddock were mostly taken by longlining from small boats, but there was also a significant trap fishery and, in some areas, the dory schooners worked close to the land. Offshore, meanwhile, over two thousand tons per year were caught on St. Pierre Bank by the schooners, nearly as much was taken from Western Bank (largely by trawlers), and lesser amounts were caught on each of the other offshore Scotian Shelf banks. In addition, there were small, if geographically extensive, haddock fisheries on Grand Bank and in the Gulf of St. Lawrence. The fish in the latter area were seasonal migrants which withdrew from the Gulf for the winter. In this period United States’ boats fished off Canada for haddock, primarily from Browns to LaHave banks, much as in the time of Rathbun ( 1887)) although they also worked other grounds from the Bay of Fundy to St. Pierre Bank (McKenzie, 1946a) and they presumably fished off their own shores too. Much of their haddock catch in the 1930s was taken by trawling. The map of haddock grounds, presented by Needler ( 193 1)) which did not distinguish longlining areas from trawling ones, nor the grounds preferred by Canadian and United States’ captains, shows that these fisheries already worked essentially the same grounds in 19 18-25 as they did in the late 1930s plus others further to the westward which McKenzie (1946a) did not consider. St. Pierre Bank had not, however, developed the relative importance in the early 1920s that it achieved 15 years later.
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By 1990, the haddock longline fishery had essentially contracted to the Scotian Shelf and, except for minor bycatches, to areas from Western Bank westwards, including inshore waters. The fishery had not only withdrawn from St. Pierre Bank (average landing in 198791 by all hook-and-line gears, 77 tons: Halliday and Clark, 1995), but also from the Gulf of St. Lawrence (average landing 1 ton), Sydney Bight (average landing 98 tons) and, to a large extent, from the Bay of Fundy (separate catch data not available). In the western offshore areas haddock production has been more persistent, and by 1990 this species was often the predominant catch of the groundfish longliners, in terms of value if not of volume. All of the western banks were, of course, fished by Canadians, the former United States fishery having been displaced by the extension of jurisdiction in 1977. In most cases, the areas fished on these banks do not seem to have changed between 1940 and 1990 (Fig. 3 and Fig. 4). However, while the famed Browns Bank winter haddock fishery (Rathbun, 1887; McKenzie, 1946a) continued into the 1980s (Halliday and Sinclair, 1987)) late in that decade the shoal water of the bank was abandoned and the fleet moved into the deeper gully between the bank and the land (Kenchington et al., 1994). There has also been an equivalent reduction in haddock longlining on Roseway Bank to that noted above for cod. Many longline captains believe that intensive trawling has caused these local changes by depleting the haddock resources and modifying bottom habitats (Kenchington and Halliday, 1994). The reasons for the major contraction in the exploitable range of haddock are not fully known. After the interviews of McKenzie (1946a) but before the northern grounds were abandoned, a trawl fishery actually expanded on Grand Bank and achieved its peak catches in 1955. Hodder (1966) and Templeman et al. (1978) have shown that the subsequent contraction from St. Pierre and Grand banks resulted, in part, from a long period of generally poor recruitment after 1956, probably as a result of adverse environmental conditions. There was a prolonged cooling trend in these waters from the early 1950s to the late 1960s (Petrie and Drinkwater, 1993). These grounds were certainly at the northern and eastern limits for this species, where the haddock might be expected to be vulnerable to cooling. Intensive fishing on the declining resource no doubt played a part too, particularly in retarding the recovery of the haddock during the warming trend of the 1970s (Petrie and Drinkwater, 1993). Whether such an explanation can also account for the disappearance of haddock from the Gulf of St. Lawrence and the Bay of Fundy is unknown. 3.3. Halibut grounds The New England fishermen discovered the deepwater halibut grounds (which can be at depths of 500 fathoms or more: Kenchington et al., 1994) in the 187Os,having previously fished this species both on the continental shelf as far east as Grand Bank and in inshore waters (Rathbun, 1887). They explored the continental slope, heading gradually eastward as they fished down each patch in turn. By the early 1880s they were fishing the slope from the edge of Georges Bank all the way to the Tail of Grand Bank and up its southeastern side to about 44’N, as well as the edges of the Northeast Channel (between Georges and Browns banks) and the Laurentian Channel (between St. Pierre Bank and Banquereau). These deepwater grounds have remained unchanged over the past century, except that they now extend all the way to Flemish Cap, presumably as a result of further exploration.
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Moreover, the continental slope along the southern edge of St. Pierre Bank and the southwestern edges of Green and Grand banks, which Rathbun ( 1887) noted as the most important area for this species, was almost the sole ground for the small Canadian deepwater halibut fishery of the late 1930s (McKenzie, 1946b) and was still identified as a prime area by the halibut longline fishermen of 1990 (Kenchington and Halliday, 1994). In his one original contribution of present relevance, Close (no date) noted the importance of the edges of Green Bank and of Banquereau for halibut in 1928. Besides this deepwater fishing by New England schooners, Rathbun ( 1887) made passing mention of an inshore fishery for halibut by small Nova Scotian boats. This continued into the 1930s and thence to the 1990s (McKenzie, 1946b; Kenchington et al., 1994). Thus, although the halibut was an almost unknown, virgin resource shortly before the time of Rathbun (1887), there has been remarkable stability in the grounds fished for it during the last century. There is certainly no evidence here of any distributional change in the northwest Atlantic halibut resource. 3.4. Hake and tusk grounds Rathbun ( 1887) mentioned that some white hake were taken on the deepwater halibut grounds off LaHave and Emerald banks. This continued in 1990, with the halibut longliners taking hake both as halibut bait and for landing (Kenchington and Halliday, 1994). Rathbun (1887) also reported that hake, tusk and pollock (Pollachius h-ens) were caught on Roseway Bank, although mostly by Nova Scotian vessels rather than New Englanders. The latter did fish hake and pollock on Browns. The general reduction in effort on Roseway Bank, noted above for cod, has affected this fishing for hake and tusk also, while they were at most a bycatch on Browns by 1990. Meanwhile, pollock have become no more than a minor bycatch of the longline fisheries, being pursued with gillnets instead (Kenchington and Halliday, 1994). Finally, Rathbun ( 1887) noted a small hake fishery in the Bay of Fundy, where local boats caught these fish in an area aptly known as ‘The Mud’. During the following century, this fishery expanded across the mouth of the Bay and, in 1990, it was the only significant longline activity in that area. A second hake fishery on muddy bottom also arose on the central Scotian Shelf. The growth of these specialized hake fisheries was presumably driven by market changes, and there is no reason to suppose that it was linked to any change in the abundance of the resource.
4. Discussion This comparison of the longline grounds fished over the past century suggests that the halibut grounds have been essentially stable since they were first discovered, and that the cod longline grounds appear to have been equally stable in their gross features although there have been more local changes which may not all be explicable as the simple consequences of human decisions. The haddock grounds have seen similar local changes but also a major contraction from eastern and northern areas. What little is known of the hake and tusk grounds is insufficient to support any conclusions about their long-term stability.
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It remains possible that the absence of more fundamental changes in the cod grounds is an artifact of the available data. Firstly, the cited sources all imply that the Gulf of St. Lawrence grounds have been of little significance to the longline fisheries. It might have been otherwise had Rathbun ( 1887) included the grounds fished by Canadians in his descriptions, had McKenzie ( 1942) considered the activity of the inshore fleet, or had Kenchington et al. ( 1994) mapped the areas exploited by boats based in Canada’s Gulf Region. That fleet landed an average of 11700 tons of hook-caught cod per year in 198791, virtually all of it being taken in the Gulf of St. Lawrence, whereas under 300 tons of the 32 500 landed by Scotia-Fundy Region hook-and-line boats came from those waters (Halliday and Clark, 1995). The distinction resulted from management regulations which largely prevented inter-Regional movements by these fleets (Parsons, 1993; Kenchington and Halliday, 1994). The development of this local longlining in the Gulf over the past century and more has most probably been the result of technological diffusion, rather than any change in cod distributions. A second, and perhaps more dramatic, change in the grounds fished has been concealed by the chance dates of the three principal studies cited here. Grand Bank was the major source of cod for the New England fleet in 1880 (Rathbun, 1887). By 1940, it was the principal source of cod for the Canadian salt fishery, although the bulk of the national catch was landed fresh and was not caught so far to the eastward (McKenzie, 1942). Thereafter, the offshore salt fishery declined and, had the survey of Kenchington and Halliday ( 1994) been carried out in 1970 or 1980, it would have found no Nova Scotian cod longlining on Grand Bank at all. In the mid-1980s, however, the offshore salt-fish industry re-appeared (although the catch is now returned fresh and salted ashore) and with it the fishery on Grand Bank. This renewed fishery was specifically targeted on the very large cod traditionally available in that area, which size of fish is required for efficient salting, as it probably also is for the profitable operation of the large longline boats necessary when fishing the Grand Banks (Kenchington and Halliday, 1994). These very large fish may have been scarce on Grand Bank in the wake of the intense trawl fishing of the early 1970s. Only with the reduction in effort that following the extension of Canadian jurisdiction in 1977 may sufficient fish have survived to reach these large sizes, and hence to make this type of fishing profitable again. If this is indeed the reason for the abandonment of, and return to, the Grand Bank grounds, it implies an expected response of the stock to extreme fishing pressure rather than any change in the underlying biological productivity. Lastly, and perhaps more seriously, the lack of a comprehensive description of inshore fishing grounds before modern times prevents any discussion of changes in those areas in earlier decades. This is unfortunate, since one of the few significant reported changes in the longline grounds in recent years has been a general withdrawal from coastal waters (Kenchington and Halliday, 1994; Kenchington et al., 1994). The general decline in fishing on Roseway Bank, which has been noted above but which is also clear in a comparison of maps of longline effort in 1960-72 (Halliday et al., 1986) with those of Halliday and Sinclair (1987) for 1982-84 and Kenchington et al. ( 1994) for 1990, may represent part of this trend; Roseway is the only near-shore bank on the Scotian Shelf which was consistently fished by the fleets whose grounds were recorded in the 1880s and 1930s. Assuming that the decline in inshore fish is real, it is not known whether it results from severe depletion of inshore stock components or simply a range contraction by a homogeneous resource
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which has drawn the fish onto preferable, offshore grounds. The latter would not violate the assumption of stable potential productivity in the assessed stock units, though the former might, while both imply a real loss of inshore productivity. In conclusion, despite the enormous increase in fishing effort on the groundfish resources of the northwest Atlantic in the past hundred years, the areas preferred for fishing with longlines in 1990 were much the same as they had been in 1880 and 1940. The present analysis has detected the known contraction in the range of haddock, while providing a reminder that it affected the Gulf of St. Lawrence and the Bay of Fundy as well as St. Pierre and Grand banks. It has also indicated a possible pattern of inter-annual variability in cod productivity on the eastern Scotian Shelf and St. Pierre Bank which may merit further investigation. Otherwise, all of the changes in the cod and haddock grounds can readily be explained as the direct effects of heavy fishing pressure on recruited year classes or of human and technical factors. The halibut grounds do not appear to have responded even to these. This comparison of fishing grounds over the past century has therefore failed to reject the common assumption of underlying stability in resource productivity, as it applies to northwest Atlantic cod and halibut, although this assumption is clearly untenable for haddock near the margin of their natural range. This apparent stability in cod and halibut productivity has been maintained in waters that are known to have the highest inter-annual variability in sea-surface temperature of any area in the temperate and tropical Atlantic (Weare, 1977). This degree of variability is seen in several data sets, and appears to be driven by changes in the strength of the Labrador Current (Petrie and Drinkwater, 1993). Since the common assumption of stable potential productivity, which underlies most stock assessments, appears generally realistic in this highly variable region, it may therefore be accepted in other sea areas provided that the species in question is not living near the limits of its natural range.
Acknowledgements I once again thank the many fishermen who provided information on their fishing grounds during our interview survey, and the various members of the Department of Fisheries and Oceans staff who have assisted with the interpretation of those data, particularly Glen Harrison, Mark Showell, Alan Sinclair, Dr. Ken Frank and Ken Drinkwater. My text was greatly improved by the comments of an anonymous referee. Finally, and most particularly, I am indebted to Dr. Ralph Halliday for initiating our survey and for his guidance throughout the work. This paper was initially prepared while the senior author was on an FAO/UNDP mission to the Marine Fisheries and Technology Station at Cox’s Bazar, Bangladesh.
References Balcom, B.A., 1977. History of the Lunenburg Fishing Industry. Lunenburg Marine Museum Society and Nova Scotia Museum, Lunenburg, 71 pp. Balcom, B.A., 1984. The Cod Fishery of Isle Royale, 1713-58. Studies in Archaeology, Architecture and History, Parks Canada, Ottawa, 88 pp.
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Close, A., no date. The North Atlantic and Gulf of St. Lawrence Fishing Grounds. Privately published, London, 28 pp + chart. Cushing, D.H., 1982. Climate and Fisheries. Academic Press, London, 373 pp. De Loture, R., 1957. History of the great fishery of Newfoundland. US Fish Wildlife Serv., Spec. Sci. Rep. Fish., 213: 147. Goode, G.B., 1887. The Fisheries and Fishery Industries of the United States. Section V. History and Methods of the Fisheries. Government Printing Office, Washington, DC, Vol. 1,808 pp. Halliday, R.G. and Clark, K.J., 1995. The Scotia-Fundy Region groundfish hook and line fisheries: A digest of quantities and sizes landed, and comparisons with other gear types. Can. Manuscr. Rep. Fish. Aquat. Sci., 2271: 178. Hahiday, R.G. and Sinclair, A.F., 1987. Fishing grounds of groundfish longliners from the Cape Sable Island area, southwestern Nova Scotia, in 1982-84. NAFO Sci. Count. Stud., 11: 75-80. Halliday, R.G., McGlade, J., Mohn, R., O’Boyle, R.N. and Sinclair, M., 1986. Resource and fishery distributions in the Gulf of Maine area in relation to the Subarea415 boundary. NAFO Sci. Count. Stud., 10: 67-92. Hanson, J.M. and Nielsen, G.A., 1992. Catches of 4T-Vn (Jan.-Apr.) cod in the 4Vs winter fishery, 1980-1992. Canadian Atlantic Fisheries Scientific Advisory Committee, Research Document 92/5 1. Hodder, V.M., 1966. Trends in the haddock fishery of ICNAF Subarea 3. ICNAF Res. Bull., 3: 55-63. Kenchington, T.J. and Halliday, R.G., 1994. A survey of fishing practices in the Scotia-Fundy Region groundfish longline fisheries. Can. Manuscr. Rep. Fish. Aquat. Sci., 2225: 642. Kenchington, T.J., Hahiday, R.G. and Harrison, G.D., 1994. Fishing grounds exploited in 1990 by groundfish longliners based in Canada’s Scotia-Fundy Region. NAFO Sci. Count. Stud., 20: 65-84. McKenzie, R.A., 1942. Canadian Atlantic offshore cod fishery east of Halifax. Bull. Fish. Res. Board Can., 61: 13. McKenzie, R.A., 1946a. The haddock fishery of grounds fished by Canadians. Bull. Fish. Res. Board Can., 69: 30. McKenzie, R.A., 1946b. The Canadian Atlantic halibut fishery. Bull. Fish. Res. Board Can., 71: 29. Moguedet, P., 1991. Variation in cod stock abundance in NAFO Subdivision 3Ps in the period 1978-1990. NAFO SCR Dot. 9 1/ 114, Serial No. N2007. Needler, A.B., 1931. The haddock. Bull. Fish. Res. Board Can., 25: 28. Parsons, L.S., 1993 Management of marine fisheries in Canada. Can. Bull. Fish. Aquat. Sci., 225: 763. Perley, M.H., 1852. Reports on the Sea and River Fisheries of New Brunswick. Queens Printer, Fredericton, 294 PP. Petrie, B. and Drinkwater, K., 1993. Temperature and salinity variability on the Scotian Shelf and in the Gulf of Maine 1945-1990. J. Geophys. Res., 98: 20079-20089. Rathbun, R., 1887. The Fisheries and Fishery Industries of the United States. Section III. The Fishing Grounds of North America. Government Printing Office, Washington, DC, xviii + 177 + xxxii pp. Sinclair, A.F., 1992. Fish distribution and partial recruitment: The case of the eastern Scotian Shelf cod. J. Northwest Atl. Fish. Sci., 13: 15-24. Templeman, W., Hodder, V.M. and Wells, R., 1978. Age, growth, year-class strength, and mortality of the haddock, Melanogrammus aeglejnus, on the southern Grand Bank and their relation to the haddock fishery of this area. ICNAFRes. Bull., 13: 31-52. Weare., B.C., 1977. Empirical orthogonal analysis of Atlantic Ocean surface temperatures. Q. J. R. Met. Sot., 103: 467-478.