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European fisheries
Marine Pollution Bulletin, Vo[. I I, pp. 31 I-315 Pergamon Press Ltd. 1980. Printed in Great Britain
Viewpoint is a column which allows authors to express their own opinions about current events.
European Fisheries D. H. CUSHING, F.R.S. Dr. Cushing was until recently Deputy Director at the Fisheries Laboratory at Lowestoft. He has taken part in the International Council for the Exploration of the Sea for a number of years and until recently was the UK member of the Advisory Committee on Fishstock Management (ACFM) of that body. In each country in Europe there are systems for collecting catch statistics and laboratories to estimate the effect of fishing upon the stocks. The International Council for the Exploration of the Sea (ICES) which was founded in 1902 is the regional body in which scientific advice is formulated as recommended by the Law of the Sea Conference. A number of Working Groups each comprized of scientists from Europe, USA and Canada meet in early summer and each examine the state of a stock or group of stocks, for example North Sea and Channel Flatfish. They write a report which assesses the state of the stocks with respect to a management objective (such as the maximum sustainable yield, MSY) and give a range of options in Total Allowable Catches (TACs), by which that objective may be achieved. Reports from the Working Groups are summarized and assessed in the Advisory Committee on Fisheries Management of ICES (ACFM), the members of which are national representatives and whose report is sent to each country's Delegate and to EEC. The Commission should recommend courses of action to the Council of Ministers, which includes agreement with third countries such as Norway and Spain, which are also represented in ICES. The management objective of ICES is the optimal sustainable yield (OSY), that is, a yield at somewhat less than the MSY in order to prevent an overshoot through the variability of stock estimates. There are precise definitions of such objectives, but for most purposes the self-evident one is to be preferred. The problem in European waters is to bring stocks to the MSY first, although there are some small stocks in northern waters exploited at the OSY. Table 1 shows the state of the stocks at the end of 1979. There are four categories of exploitation, underexploited, exploited at about the fight rate (at OSY or MSY), overexploited, and a ban on catches. A stock is considered to be overexploited if the fishing mortality suffered by the stock is greater than that needed to take the maximum sustainable yield; in some cases the present level of fishing mortality is two to three times greater than necessary. Of the 43 stocks examined in the Northeast Atlantic, catches are banned in 5, and 18 are overexploited. As might be expected the larger and commercially important stocks are those which tend to be overexploited. When we discuss overexploitation it is useful to distinguish between growth overfishing and recruitment overfishing. Many demersal fish grow as individuals by as much as an order of magnitude during their adult lives after
maturation. Provided that recruitment, the magnitude of the incoming year classes, remains constant under the pressure of fishing, the problem of growth overfishing is to maximize the two countervailing processes, the growth in weight of individuals and the loss in numbers from the population. A curve of field-per-recruit on fishing mortality has a distinct maximum in fishing mortality or the flat top of an asymptote in which case a practical maximum can be readily defined. In either case the management objective can be readily formulated and advice on how to achieve it can be given. But it requires that the small fish are caught as rarely as possible; in general fish should not be caught before they have matured. Very often this ideal is not realized and in discussing this problem fisheries biologists talk of the exploitation pattern, the distribution of fishing mortality with age, the maximal rate being exerted on the adult and larger fish. Recruitment overfishing occurs when the magnitude of recruitment declines as fishing intensity increases and stock must then decrease; a vicious circle is established which must lead to stock collapse and extinction of the fishery. It is no accident that the pelagic fish which do not grow very much during their adult lives tend to suffer more from recruitment overfishing: they do not lay as many eggs as demersal fish and hence the populations depend much more on the best survival between hatching and recruitment. The stocks from which catches are banned in the Northeast Atlantic are all herring stocks, with one exception, the cod stock off East Greenland (which has collapsed naturally as part of a climatic change). In general there are two failures in the management of the fisheries: (a) too many small fish have been caught, which has at least prevented the recovery of the herring stocks (and may have caused the collapses) and has inhibited the best exploitation of many of the demersal stocks; (b) too much fishing effort, too many fishermen and too many ships are deployed on the adult stocks. The first tends to generate recruitment overfishing and the second growth overfishing and sometimes both can occur in the same stock as perhaps today happens in the North Sea sole stock. We shall now consider some of the difficulties in exploitation pattern, the capture of small fish, which have caused poor management in European waters. One of the most remarkable developments since the Second World War in the North Sea has been the development of industrial fisheries. Throughout the world more than fifteen million tons of herring-like (or sardine-like) fishes are caught each year for 311
Marine Pollution Bulletin
TABLE 1 State of the stocks in the North-east Atlantic. Herring-like Fishes
Flat fishes
Cod-like Fishes
Mackerel
Perch-like Fishes
e~
-v O t~
e-
w.
~,
"7-. O
Barents Sea Norwegian Sea Greenland Iceland Faroes North Sea English Channel Celtic Sea Irish Sea W. Scotland Biscay - Shetland Key:
x ® • (3 ?
•
~
g
._
~-
'~
~9
n
®
• o
0 • •
•
•
® ®
®
• •
X
•
•
x
® ×
•
o
?
•
x
X
o
• •
•
•
®
x
®
Exploited at less than MSY Exploited at MSY Overexploited Catches banned Exploitation not yet understood
o
x ® • (3 ?
Total catches in 1977: 10 344 000 (7%) 7 2 582 000" (50%) 19 1 769 000 (34%) 5 130 000 (3°70) 1 304 000 (6070) 5 129 000
344 000 (9%) I 415 000 (36%) 1 769 000 (45%) 130 000 (3070) 304 000 (8070) 3 962 000
*Includes I 167 0 0 0 t o n s o f N o r w a y p o u t a n d s a n d e e l i n t h e N o r t h Sea.
conversion to fish meal for animal feeding stuffs. In the North Sea, Danish fishermen started their industrial fishery for immature herring in the early fifties perhaps as the result of a natural change in the recruitment pattern; by 1955, catches had reached about 100000 tons. During the early sixties, the Danish fishermen turned their attention to Norway pout, a small gadoid caught in the northern North Sea where young haddock and whiting live. In this period they also caught sprats in large quantities. In summer time, they fished for sandeels on the tops of banks off Norfolk, in the eastern North Sea and in the Northern North Sea. By 1974 Danish, Norwegian, Faroese and British fishermen were landing about 1.8 million tons of fish for industrial purposes. There is nothing wrong with an industrial fishery as such, but there are occasions when other fisheries may be damaged by the activities of industrial fishermen. The sandeel fishery probably does not damage another fishery, so far as we can see because the by-catches of other fish are low, probably less than 50/0. The first effect of industrial fisheries was that on the herring stocks. During the late fifties and the sixties, catches of immature herring reached as much as 200 000 tons per year in some years. The fishing mortality on the adult stock was high, perhaps two to three times as much as it should have been. The three spawning groups, Downs, Dogger and Buchan collapsed in sequence between the late fifties and the late sixties. Finally, the decline of recruitment as function of adult stock was established and the advice given by ICES was first a restricted quota and then in 1978, a ban on catches in the North Sea. The ban was established in a UK national measure which was subsequently adopted by EEC. We have not precise enough information to establish whether the collapse was due to the capture of immature fish in the industrial fishery or to the excessive fishing mortality on the 312
older fish; what we can say now is that the combination of both fisheries led inevitably to collapse. Similar collapses have occurred in the Norwegian Sea, where the AtlantoScandian herring stock collapsed under the pressure of an industrial fishery for immature fish and an avid purse seine fishery for the adults. The stock of herring in the Celtic Sea collapsed in the middle seventies as did that off the West coast of Scotland in the late seventies; in neither fishery was there a distinct fishery for immature fish although many must have been caught inadvertently. Four major herring stocks have collapsed and the cause has been recruitment overfishing. The purpose of the bans on the capture of herring is to allow the stocks to recover. In the North Sea, young herring are caught as by-catch in the sprat fishery in which perhaps 400 000 tons are caught each winter for industrial purposes. Recovery of the herring stock depends upon the appearance of a strong new year class, part of which must be caught in the sprat fishery. That proportion depends on the relative strengths of herring and sprat year classes and the worst combination is a poor sprat recruitment with a strong herring year class and then the by-catches are potentially high. Therefore the by-catches must be rigidly enforced to a level of 10% of each individual catch. Even then if the sprat catches are high considerable damage could be done to the chances of recovery of the herring stock. For example, a bycatch of 40 000 tons would represent about half the present stock of herring in the Southern North Sea (the total stock of herring in the North Sea is greater, 250 000-400 000 tons). The point here is that the recovering stocks depend on the distinct recruitments from three spawning groups and although this cannot be shown, the sprat fishery may select one of them. Hence the industrial fishery for juvenile herring in the past contributed considerably to the collapse
Volume 11/Number I l/November 1980
of the herring stocks and that for sprats at the present time must delay recovery to some degree. The industrial fishery for Norway pout lasts from August in one year, to March in the following year. In January, February and March catches of whiting in the past have been very high which has suggested the possibility of directed fishing for whiting having taken place. In October, November and December the young haddock of the year descend to the sea bed and mix with the Norway pout. In some years the catches in weight of immature haddock have exceeded those of the adults and indeed the potential capture of adult haddock and whiting have been much reduced in the past by this industrial fishery. It can be shown that the value of a haddock or whiting, had it been allowed to grow and enter the adult fishery, would have been between thirteen and fifteen times that in the industrial fishery. In the years before 1975 it was estimated that the loss to the adult fisheries amounted to about 100 000 tons of both haddock and whiting. The effect of this industrial fishery for Norway pout was to reduce the stock of adult haddock and whiting considerably and hence the best yield of weight was not available to fishermen. The Norway pout box is an area between 56 ° 30'N and 60 ° 0' N extending out to the median line between October and March (about 2°E); within this area the capture of Norway pout has been prohibited. It was established as a UK national measure and enforced by Fishery Protection vessels of the UK; during the history of the measure, there have been some boxes of different areas, some of which have been adopted by the EEC. The present box has been in force since 1978 and Scottish fishermen believe that it has been effective because they have noticed more young haddock and whiting in their catches since then. The effect of the Norway pout box on the Danish industrial fleets has been considerable. It was thought that they would have been able to divert their ships to the north of the box where Norway pout is abundant and where the stocks of young haddock and whiting are less. However, they were unable to do so presumably because the steaming distance was somewhat greater which indicates the rather slender economic margin on which the industrial fleets work. The Norwegian fishermen and Faroese fishermen were able to continue working outside the Norway pout box. The Danish fishermen have claimed that it is possible to catch Norway pout without haddock and whiting in deep water ( > 140 m) and there is some information to suggest that this is true. Indeed a recent ICES Working Group has analysed the available data and has concluded that it would be worth while conducting research at sea to establish where and when such catches could be made. This is an important point because if the industrial fishery for Norway pout can countinue without damaging the haddock and whiting stock, it should do so. The catches of Norway pout by the Danish fleet have been much reduced, partly by the Norway pout box and partly by their exclusion from the Norwegian sector of the North Sea, where it is unlikely that young haddock and young whiting live in quantity. A 5 o7oby-catch is enforced upon the fishermen by the Danish authorities; this measure, combined with reduced opportunities and a possible restricted fishery in deeper waters might well allow the industrial fishery to continue with least damage to the adult stocks of haddock and whiting. In recent years, Danish scientists have developed a
multispecies model. Eleven stocks in the North Sea were divided into three or four groups and within one group the food was shared in a particular way. If one stock within the group collapsed due to recruitment overfishing, then the food is diverted to one of the others and it must increase. During the sixties the herring and mackerel stocks collapsed and the cod-like fishes (including Norway pout) increased. Hence the excess of food released by herring and mackerel was perhaps diverted into cod-like fishes or into the industrial species such as Norway pout. Indeed an inverse relationship was established between herring and mackerel on the one hand and Norway pout and sandeel on the other, which, however, may have contained two time series independent of each other. In science there is no evidence yet that food switches from one stock to another within a group primarily because most of the excess food might well be taken up by planktonic predators which are more abundant than fishes. In management the implications would be more severe, that a stock could be exploited to extinction (or very low levels) and that this would not matter because it would be succeeded by another. If we are only interested in protein, as is an industrial fisherman, this would be a perfectly good system of management, in particular because it needs no administrative superstructure. However, because the system embraces most of the important commercial fish stocks, it requires that the industrial fishery takes precedence over any fishery for human consumption. In other words animals should eat prime fish before people do. But the demand for prime fish remains much higher than that for fish meal and the management objectives of ICES state that catches should be made at the optimal sustainable yield with the best exploitation p a t t e r n - which means that small and immature fish should not be taken because of the ever present and rampant danger of recruitment overfishing. There is nothing wrong with an industrial fishery even if the price of fish for industrial purposes is low. So long as people want to eat fish the price of that fish should be as low as possible, which means that the stocks should be as abundant as possible. The catch per unit of effort, the index of profit and of stock, should be as high as possible and then the price of fish would be as low as possible. It follows that stocks should be exploited at the maximum sustainable yield (in the loose definition used above) and that small fish should not be caught in industrial fisheries. In the North Sea industrial fisheries, that for sandeels in summer should continue freely, that for Norway pout might be prosecuted in a limited way in deep water and that for sprats might be restrained if it interferes with the best exploitation of the herring stock after it has recovered. One of the triumphs of fisheries research was to show that the maximum sustainable yield could be obtained in a single stock of demersal fish by merely increasing the mesh size rather than by putting fishermen out of work. However, most fishermen exploit a mixture of stocks which means that the mesh size appropriate to the smallest fish is the one that should be used; in the North Sea, the smallest fishes are haddock and sole. For some years ICES has recommended that the mesh sizes in the North Sea should go up from 70 to 90 mm. In northern waters, where fishes are rather bigger and the mix of stocks less complex, current meshes range between 120 mm and 150 mm, which would be those appropriate to plaice and cod in the North Sea were it possible to catch them without other fishes. 313
Marine Pollution Bulletin If the mesh sizes are right it is still possible to increase the number of ships and then the fishing mortality increases and the average size of fishes decreases. This is what happened during the thirties and mesh sizes decreased in order to maintain weight on the deck. At the present time too much effort is exerted in the North Sea and for similar reasons fishermen are loth to accept larger mesh sizes. Whenever an increased mesh size is introduced there is a short term loss before the new year class comes in of somewhat bigger fish. It is always hard to convince fishermen that a short term loss has to be accepted rather like a poor year class in order to reach the permanency of a long term gain. The procedure can be mitigated somewhat by trying to introduce an increase in mesh size when a big year class is coming into the fishery. However in the North Sea fishermen discard fish in rather large quantities. They tend to use mesh sizes which are effectively smaller than they should because they employ lifting devices which act as blinders. They obtain large weights on the deck but they retain only the larger fish which fetch the higher prices. Nearly always the market minimum size is greater than the minimum landing size which is linked to the mesh size. The solution to this problem is use larger mesh sizes, mesh sizes which match the market sizes. Then fish will not be discarded, dead. One might expect that fishermen who only wanted larger haddock, whiting or sole would use the mesh sizes needed to catch them. For some inexplicable reason they prefer the larger weight on deck with the additional labour of discarding dead small fish. Like part of the industrial fisheries, to discard young and immature fish is to abuse the exploitation pattern of the stocks. The little fish discarded should be allowed to grow into the adult fisheries just as should those caught in the industrial fisheries. The simple answer to this problem in the North Sea is to increase mesh sizes to 90 mm as soon as possible. In the Irish Sea and Celtic Sea there is another problem of exploitation pattern. French and Irish fishermen prefer to catch Nephrops, the Dublin Bay prawn (or scampi) with very small meshed nets of about 40 mm. In the North Sea the same animals can be caught perfectly well with meshes of 70 mm. There are two consequences (a) small Nephrops are caught in numbers which are much too great with the consequence that the average size has gone down (b) small whiting are discarded in large numbers; indeed in numbers more whiting have been discarded than caught in the Irish Sea. With increased mesh sizes (to 70 mm), the fishermen would suffer a short term loss of short duration and quite soon would start to catch larger animals. The price per unit weight of Nephrops increases very sharply with weight and the financial rewards to the Nephrops fishermen would be considerable. At the present time they catch large weight on deck and spend hours working through the catch for the large animals they want and discard the rest, dead. Hence an increase in mesh size to 70 mm in the Irish Sea and in the Celtic Sea would yield larger animals with less labour and catches of larger whiting which could be sold rather than discarded. A related problem is that of the hake. Hake were caught off Ireland and the west coast of Scotland by British fishermen who landed their catches predominantly in Milford Haven. During the late fifties and early sixties catches declined and now hake is not caught much by British 314
fishermen and the port of Milford has lost much of its fishing community. Part of the trouble was the efficient use of high headline trawls by French and Spanish fishermen, but another part was the exploitation of "needle" hake off the North coast of Spain and of very small hake by French Nephropstrawlers in La Grande Vasi~re. This is a mud bank off Brittany where the young hake grow up. A recent ICES Working Group has estimated that three quarters of the catch of hake in the Bay of Biscay is below the minimum landing size. Consequently the hake's exploitation pattern is being grossly abused. The "needle" hake fishery of long thin little fish is an old traditional one. That on La Grande Vasi~re is relatively new, having developed with the price of shrimp during the sixties. There is no reason why French Nephrops fishermen should not earn more money by catching larger shrimps with bigger mesh sizes because like their compatriots in the Irish and Celtic Seas they discard the bulk of their catches. An increase in mesh size in the Nephrops fishery and a reduction in the "needle" hake fishery would restore the hake stock and bring back potential catches to British fishermen. A further sample of a somewhat poor exploitation pattern is found in the mackerel fishery. Since about 1967 or so dense shoals of mackerel were found in Cornish waters in winter and catches increased there during the early seventies. When Russian and East European trawlers left European waters in 1977, very large catches were made by large British trawlers and were trans-shipped to Russian vessels. British catches off Cornwall and in the Minch have been in excess of 300 000 tons. In the Minch and on the Continental Shelf, the fish caught are large and old. Off Cornwall, however, a proportion of small fish is taken of between 25 cm and 30 cm in length. ICES has recommended that there be a closed area in Cornish waters in the western English Channel and in the Celtic Sea for much of the year; in other words fishing should be restricted to the midwinter period when the proportion of large fish is highest. Thus the exploitation pattern can be improved not only by increasing mesh sizes, but also by preventing the capture of small fish in a given area. Quite recently it has been shown that if the capture of small fish in Cornish waters were completely stopped (i.e. the area remained closed all the year round except for handliners and local trawlers) and if fishing were limited to the Continental Shelf and to the Minches, an extra 150 000 tons would be available to the fishermen. There is little danger that the mackerel stock would collapse in the immediate future because a strong year class is about to enter the fishery. However, if the present fishing mortality were sustained without a restraint on the capture of small fish in the Cornish area, the mackerel stock would collapse. This is the first time that fisheries biologists have been able to set down the conditions for collapse before it happens and it follows that the capture of small fish off Cornwall should be prevented because the alternative is to put between one third and one half of the international fishing fleet out of work (because there is little alternative employment). The capture of small fish should be eliminated in the North Sea demersal fisheries, in the hake fisheries and in the mackerel fishery. However, the improvement of exploitation pattern is only part of the conservation needed. The fishing mortality on cod, haddock and whiting in the North Sea is two to three times greater than it need be, even with a potential mesh size of 90 mm. Much the same is true
V o l u m e I l / N u m b e r I l / N o v e m b e r 1980
of the Arcto-Norwegian cod stock in the Barents Sea, of the sole stock in the North Sea and of cod and haddock stocks to the west of the British Isles. When the mesh size has reached its optimum size and the fishing mortality is still too high, catches must be reduced by quota or by effort regulation. In theory, effort regulation is the most desirable because fishing mortality is considered to be a direct function of fishing effort. This, however is very variable and statistics are lacking in many countries. When they declared a 200 mile limit, the Canadians cut foreign fishing effort by 40% and enforced it well, with the result that the cod stocks are recovering quickly. But this is a special case which does not apply to European waters from which the Russians and East Europeans have already been evicted. In European waters effort regulation on its own would be very difficult to manage. Total Allowable Catches (TACs) or catch quotas were introduced in ICNAF (International Commission for North West Atlantic Fisheries) in 1970 and into NEAFC (North East Atlantic Fisheries Commission) in 1974. Today all stocks of any value are under some sort of quota arrangements. In the absence of a Common Fisheries Policy, the EEC has not yet established quota regulations although quotas are published to which many, but not all, nations adhere. In the absence of quota regulation, the excess of catch over quota is always blamed on the foreigner. The fact that catches do not exceed quotas except in some well publicized instances is in itself evidence that fishing effort is much too high. But the next stage as consequence of
a Common Fisheries Policy must be the restriction of fishing by reduced quotas with monthly catch reporting. When quotas begin to bite with a system of enforcement linked to catch reports, there will be complaints, but they will be common and shared amongst fishermen of all nations. In The Fish Gate, published in 1943, Michael Graham stated the Great Law of Fishing, that free fishing becomes unprofitable. Therefore fishing effort has to be restrained in order that fishermen should make a living and that people can have steady supplies of fish at reasonable prices. One of the great dangers of management by the coastal state is that it could lead to overexploitation because most fish stock management has so far been international. There is no evidence yet that international management is to be preferred to that by the coastal state, but in European waters there is a very great opportunity to show that international management can be made to work. Not only do we need to control fishing effort by means of catch quota with monthly catch reporting, but the exploitation pattern needs to be improved in a number of fisheries. Michael Graham quotes the results of an experiment made at sea before the Second World War. Two ships were fishing alongside each other, one with the usual mesh of that period and the other with a slightly larger one; the larger mesh caught more large haddocks and fewer small ones and the trawler with the larger mesh earned slightly more. The fishermen's fears that an increase in mesh size will reduce their earnings are unjustified.
Marine Pollution Bulletin, Vol. I I, pp. 315-317
Pergamon Press Ltd. 1980.Printed in Great Britain
Pelagic Tar off Georgia and Florida m Relation to Physical Processes CAMILLE CORDES* LARRY ATKINSON,I- RICHARD LEE and JACK BLANTON
Skidway Institute of Oceanography, P.O. Box 13687, Savannah, Georgia31406, USA *Present address: S o u t h a m p t o n College, S o u t h a m p t o n , N e w York 11968, U S A t T o w h o m inquiries s h o u l d be a d d r e s s e d .
Following the Ixtoc I oil rig blowout in Campeche Bay we hypothesized that resulting tarballs should eventually appear in the Gulf Stream off Gerogia and that because of dynamic barriers in the innershelf little would reach nearshore areas. To test these hypotheses, surface tows to collect floating tar were taken off the coasts of Georgia and Florida in October and December, 1979. No tar was found within 40 km of the shore. All samples more than 40 km offshore contained some tar. The mean concentration was 0.82 mg m -2 with a range of 0.01-5.6 mg m -2. Closely spaced sampling showed extreme variation but trends were consistent. Perylene was the most abundant compound in the tarbails.
On 3 June 1979, the exploratory petroleum well Ixtoc I, located in Campeche Bay, Gulf of Mexico, experienced a blowout. More than 20 000 barrels per day of paraffin base crude oil spilled into the Gulf of Mexico. According to US Coast Guard sources, on 27 August 1979, heavy tarbaU concentrations were located about 120 miles southeast of Corpus Cristi. If the tar continued to travel with predominant currents, it would eventually be entrained in the Loop Current, exit the Gulf through the Straits of Florida and be advected north by the Gulf Stream. Levy & Walton (1976) define tarballs as oil which has been exposed to a variety of biological, chemical, physical and geological processes that alter its chemical composition 315
Viewpoint is a column which allows authors to express their own opinions about current events.
European Fisheries D. H. CUSHING, F.R.S. Dr. Cushing was until recently Deputy Director at the Fisheries Laboratory at Lowestoft. He has taken part in the International Council for the Exploration of the Sea for a number of years and until recently was the UK member of the Advisory Committee on Fishstock Management (ACFM) of that body. In each country in Europe there are systems for collecting catch statistics and laboratories to estimate the effect of fishing upon the stocks. The International Council for the Exploration of the Sea (ICES) which was founded in 1902 is the regional body in which scientific advice is formulated as recommended by the Law of the Sea Conference. A number of Working Groups each comprized of scientists from Europe, USA and Canada meet in early summer and each examine the state of a stock or group of stocks, for example North Sea and Channel Flatfish. They write a report which assesses the state of the stocks with respect to a management objective (such as the maximum sustainable yield, MSY) and give a range of options in Total Allowable Catches (TACs), by which that objective may be achieved. Reports from the Working Groups are summarized and assessed in the Advisory Committee on Fisheries Management of ICES (ACFM), the members of which are national representatives and whose report is sent to each country's Delegate and to EEC. The Commission should recommend courses of action to the Council of Ministers, which includes agreement with third countries such as Norway and Spain, which are also represented in ICES. The management objective of ICES is the optimal sustainable yield (OSY), that is, a yield at somewhat less than the MSY in order to prevent an overshoot through the variability of stock estimates. There are precise definitions of such objectives, but for most purposes the self-evident one is to be preferred. The problem in European waters is to bring stocks to the MSY first, although there are some small stocks in northern waters exploited at the OSY. Table 1 shows the state of the stocks at the end of 1979. There are four categories of exploitation, underexploited, exploited at about the fight rate (at OSY or MSY), overexploited, and a ban on catches. A stock is considered to be overexploited if the fishing mortality suffered by the stock is greater than that needed to take the maximum sustainable yield; in some cases the present level of fishing mortality is two to three times greater than necessary. Of the 43 stocks examined in the Northeast Atlantic, catches are banned in 5, and 18 are overexploited. As might be expected the larger and commercially important stocks are those which tend to be overexploited. When we discuss overexploitation it is useful to distinguish between growth overfishing and recruitment overfishing. Many demersal fish grow as individuals by as much as an order of magnitude during their adult lives after
maturation. Provided that recruitment, the magnitude of the incoming year classes, remains constant under the pressure of fishing, the problem of growth overfishing is to maximize the two countervailing processes, the growth in weight of individuals and the loss in numbers from the population. A curve of field-per-recruit on fishing mortality has a distinct maximum in fishing mortality or the flat top of an asymptote in which case a practical maximum can be readily defined. In either case the management objective can be readily formulated and advice on how to achieve it can be given. But it requires that the small fish are caught as rarely as possible; in general fish should not be caught before they have matured. Very often this ideal is not realized and in discussing this problem fisheries biologists talk of the exploitation pattern, the distribution of fishing mortality with age, the maximal rate being exerted on the adult and larger fish. Recruitment overfishing occurs when the magnitude of recruitment declines as fishing intensity increases and stock must then decrease; a vicious circle is established which must lead to stock collapse and extinction of the fishery. It is no accident that the pelagic fish which do not grow very much during their adult lives tend to suffer more from recruitment overfishing: they do not lay as many eggs as demersal fish and hence the populations depend much more on the best survival between hatching and recruitment. The stocks from which catches are banned in the Northeast Atlantic are all herring stocks, with one exception, the cod stock off East Greenland (which has collapsed naturally as part of a climatic change). In general there are two failures in the management of the fisheries: (a) too many small fish have been caught, which has at least prevented the recovery of the herring stocks (and may have caused the collapses) and has inhibited the best exploitation of many of the demersal stocks; (b) too much fishing effort, too many fishermen and too many ships are deployed on the adult stocks. The first tends to generate recruitment overfishing and the second growth overfishing and sometimes both can occur in the same stock as perhaps today happens in the North Sea sole stock. We shall now consider some of the difficulties in exploitation pattern, the capture of small fish, which have caused poor management in European waters. One of the most remarkable developments since the Second World War in the North Sea has been the development of industrial fisheries. Throughout the world more than fifteen million tons of herring-like (or sardine-like) fishes are caught each year for 311
Marine Pollution Bulletin
TABLE 1 State of the stocks in the North-east Atlantic. Herring-like Fishes
Flat fishes
Cod-like Fishes
Mackerel
Perch-like Fishes
e~
-v O t~
e-
w.
~,
"7-. O
Barents Sea Norwegian Sea Greenland Iceland Faroes North Sea English Channel Celtic Sea Irish Sea W. Scotland Biscay - Shetland Key:
x ® • (3 ?
•
~
g
._
~-
'~
~9
n
®
• o
0 • •
•
•
® ®
®
• •
X
•
•
x
® ×
•
o
?
•
x
X
o
• •
•
•
®
x
®
Exploited at less than MSY Exploited at MSY Overexploited Catches banned Exploitation not yet understood
o
x ® • (3 ?
Total catches in 1977: 10 344 000 (7%) 7 2 582 000" (50%) 19 1 769 000 (34%) 5 130 000 (3°70) 1 304 000 (6070) 5 129 000
344 000 (9%) I 415 000 (36%) 1 769 000 (45%) 130 000 (3070) 304 000 (8070) 3 962 000
*Includes I 167 0 0 0 t o n s o f N o r w a y p o u t a n d s a n d e e l i n t h e N o r t h Sea.
conversion to fish meal for animal feeding stuffs. In the North Sea, Danish fishermen started their industrial fishery for immature herring in the early fifties perhaps as the result of a natural change in the recruitment pattern; by 1955, catches had reached about 100000 tons. During the early sixties, the Danish fishermen turned their attention to Norway pout, a small gadoid caught in the northern North Sea where young haddock and whiting live. In this period they also caught sprats in large quantities. In summer time, they fished for sandeels on the tops of banks off Norfolk, in the eastern North Sea and in the Northern North Sea. By 1974 Danish, Norwegian, Faroese and British fishermen were landing about 1.8 million tons of fish for industrial purposes. There is nothing wrong with an industrial fishery as such, but there are occasions when other fisheries may be damaged by the activities of industrial fishermen. The sandeel fishery probably does not damage another fishery, so far as we can see because the by-catches of other fish are low, probably less than 50/0. The first effect of industrial fisheries was that on the herring stocks. During the late fifties and the sixties, catches of immature herring reached as much as 200 000 tons per year in some years. The fishing mortality on the adult stock was high, perhaps two to three times as much as it should have been. The three spawning groups, Downs, Dogger and Buchan collapsed in sequence between the late fifties and the late sixties. Finally, the decline of recruitment as function of adult stock was established and the advice given by ICES was first a restricted quota and then in 1978, a ban on catches in the North Sea. The ban was established in a UK national measure which was subsequently adopted by EEC. We have not precise enough information to establish whether the collapse was due to the capture of immature fish in the industrial fishery or to the excessive fishing mortality on the 312
older fish; what we can say now is that the combination of both fisheries led inevitably to collapse. Similar collapses have occurred in the Norwegian Sea, where the AtlantoScandian herring stock collapsed under the pressure of an industrial fishery for immature fish and an avid purse seine fishery for the adults. The stock of herring in the Celtic Sea collapsed in the middle seventies as did that off the West coast of Scotland in the late seventies; in neither fishery was there a distinct fishery for immature fish although many must have been caught inadvertently. Four major herring stocks have collapsed and the cause has been recruitment overfishing. The purpose of the bans on the capture of herring is to allow the stocks to recover. In the North Sea, young herring are caught as by-catch in the sprat fishery in which perhaps 400 000 tons are caught each winter for industrial purposes. Recovery of the herring stock depends upon the appearance of a strong new year class, part of which must be caught in the sprat fishery. That proportion depends on the relative strengths of herring and sprat year classes and the worst combination is a poor sprat recruitment with a strong herring year class and then the by-catches are potentially high. Therefore the by-catches must be rigidly enforced to a level of 10% of each individual catch. Even then if the sprat catches are high considerable damage could be done to the chances of recovery of the herring stock. For example, a bycatch of 40 000 tons would represent about half the present stock of herring in the Southern North Sea (the total stock of herring in the North Sea is greater, 250 000-400 000 tons). The point here is that the recovering stocks depend on the distinct recruitments from three spawning groups and although this cannot be shown, the sprat fishery may select one of them. Hence the industrial fishery for juvenile herring in the past contributed considerably to the collapse
Volume 11/Number I l/November 1980
of the herring stocks and that for sprats at the present time must delay recovery to some degree. The industrial fishery for Norway pout lasts from August in one year, to March in the following year. In January, February and March catches of whiting in the past have been very high which has suggested the possibility of directed fishing for whiting having taken place. In October, November and December the young haddock of the year descend to the sea bed and mix with the Norway pout. In some years the catches in weight of immature haddock have exceeded those of the adults and indeed the potential capture of adult haddock and whiting have been much reduced in the past by this industrial fishery. It can be shown that the value of a haddock or whiting, had it been allowed to grow and enter the adult fishery, would have been between thirteen and fifteen times that in the industrial fishery. In the years before 1975 it was estimated that the loss to the adult fisheries amounted to about 100 000 tons of both haddock and whiting. The effect of this industrial fishery for Norway pout was to reduce the stock of adult haddock and whiting considerably and hence the best yield of weight was not available to fishermen. The Norway pout box is an area between 56 ° 30'N and 60 ° 0' N extending out to the median line between October and March (about 2°E); within this area the capture of Norway pout has been prohibited. It was established as a UK national measure and enforced by Fishery Protection vessels of the UK; during the history of the measure, there have been some boxes of different areas, some of which have been adopted by the EEC. The present box has been in force since 1978 and Scottish fishermen believe that it has been effective because they have noticed more young haddock and whiting in their catches since then. The effect of the Norway pout box on the Danish industrial fleets has been considerable. It was thought that they would have been able to divert their ships to the north of the box where Norway pout is abundant and where the stocks of young haddock and whiting are less. However, they were unable to do so presumably because the steaming distance was somewhat greater which indicates the rather slender economic margin on which the industrial fleets work. The Norwegian fishermen and Faroese fishermen were able to continue working outside the Norway pout box. The Danish fishermen have claimed that it is possible to catch Norway pout without haddock and whiting in deep water ( > 140 m) and there is some information to suggest that this is true. Indeed a recent ICES Working Group has analysed the available data and has concluded that it would be worth while conducting research at sea to establish where and when such catches could be made. This is an important point because if the industrial fishery for Norway pout can countinue without damaging the haddock and whiting stock, it should do so. The catches of Norway pout by the Danish fleet have been much reduced, partly by the Norway pout box and partly by their exclusion from the Norwegian sector of the North Sea, where it is unlikely that young haddock and young whiting live in quantity. A 5 o7oby-catch is enforced upon the fishermen by the Danish authorities; this measure, combined with reduced opportunities and a possible restricted fishery in deeper waters might well allow the industrial fishery to continue with least damage to the adult stocks of haddock and whiting. In recent years, Danish scientists have developed a
multispecies model. Eleven stocks in the North Sea were divided into three or four groups and within one group the food was shared in a particular way. If one stock within the group collapsed due to recruitment overfishing, then the food is diverted to one of the others and it must increase. During the sixties the herring and mackerel stocks collapsed and the cod-like fishes (including Norway pout) increased. Hence the excess of food released by herring and mackerel was perhaps diverted into cod-like fishes or into the industrial species such as Norway pout. Indeed an inverse relationship was established between herring and mackerel on the one hand and Norway pout and sandeel on the other, which, however, may have contained two time series independent of each other. In science there is no evidence yet that food switches from one stock to another within a group primarily because most of the excess food might well be taken up by planktonic predators which are more abundant than fishes. In management the implications would be more severe, that a stock could be exploited to extinction (or very low levels) and that this would not matter because it would be succeeded by another. If we are only interested in protein, as is an industrial fisherman, this would be a perfectly good system of management, in particular because it needs no administrative superstructure. However, because the system embraces most of the important commercial fish stocks, it requires that the industrial fishery takes precedence over any fishery for human consumption. In other words animals should eat prime fish before people do. But the demand for prime fish remains much higher than that for fish meal and the management objectives of ICES state that catches should be made at the optimal sustainable yield with the best exploitation p a t t e r n - which means that small and immature fish should not be taken because of the ever present and rampant danger of recruitment overfishing. There is nothing wrong with an industrial fishery even if the price of fish for industrial purposes is low. So long as people want to eat fish the price of that fish should be as low as possible, which means that the stocks should be as abundant as possible. The catch per unit of effort, the index of profit and of stock, should be as high as possible and then the price of fish would be as low as possible. It follows that stocks should be exploited at the maximum sustainable yield (in the loose definition used above) and that small fish should not be caught in industrial fisheries. In the North Sea industrial fisheries, that for sandeels in summer should continue freely, that for Norway pout might be prosecuted in a limited way in deep water and that for sprats might be restrained if it interferes with the best exploitation of the herring stock after it has recovered. One of the triumphs of fisheries research was to show that the maximum sustainable yield could be obtained in a single stock of demersal fish by merely increasing the mesh size rather than by putting fishermen out of work. However, most fishermen exploit a mixture of stocks which means that the mesh size appropriate to the smallest fish is the one that should be used; in the North Sea, the smallest fishes are haddock and sole. For some years ICES has recommended that the mesh sizes in the North Sea should go up from 70 to 90 mm. In northern waters, where fishes are rather bigger and the mix of stocks less complex, current meshes range between 120 mm and 150 mm, which would be those appropriate to plaice and cod in the North Sea were it possible to catch them without other fishes. 313
Marine Pollution Bulletin If the mesh sizes are right it is still possible to increase the number of ships and then the fishing mortality increases and the average size of fishes decreases. This is what happened during the thirties and mesh sizes decreased in order to maintain weight on the deck. At the present time too much effort is exerted in the North Sea and for similar reasons fishermen are loth to accept larger mesh sizes. Whenever an increased mesh size is introduced there is a short term loss before the new year class comes in of somewhat bigger fish. It is always hard to convince fishermen that a short term loss has to be accepted rather like a poor year class in order to reach the permanency of a long term gain. The procedure can be mitigated somewhat by trying to introduce an increase in mesh size when a big year class is coming into the fishery. However in the North Sea fishermen discard fish in rather large quantities. They tend to use mesh sizes which are effectively smaller than they should because they employ lifting devices which act as blinders. They obtain large weights on the deck but they retain only the larger fish which fetch the higher prices. Nearly always the market minimum size is greater than the minimum landing size which is linked to the mesh size. The solution to this problem is use larger mesh sizes, mesh sizes which match the market sizes. Then fish will not be discarded, dead. One might expect that fishermen who only wanted larger haddock, whiting or sole would use the mesh sizes needed to catch them. For some inexplicable reason they prefer the larger weight on deck with the additional labour of discarding dead small fish. Like part of the industrial fisheries, to discard young and immature fish is to abuse the exploitation pattern of the stocks. The little fish discarded should be allowed to grow into the adult fisheries just as should those caught in the industrial fisheries. The simple answer to this problem in the North Sea is to increase mesh sizes to 90 mm as soon as possible. In the Irish Sea and Celtic Sea there is another problem of exploitation pattern. French and Irish fishermen prefer to catch Nephrops, the Dublin Bay prawn (or scampi) with very small meshed nets of about 40 mm. In the North Sea the same animals can be caught perfectly well with meshes of 70 mm. There are two consequences (a) small Nephrops are caught in numbers which are much too great with the consequence that the average size has gone down (b) small whiting are discarded in large numbers; indeed in numbers more whiting have been discarded than caught in the Irish Sea. With increased mesh sizes (to 70 mm), the fishermen would suffer a short term loss of short duration and quite soon would start to catch larger animals. The price per unit weight of Nephrops increases very sharply with weight and the financial rewards to the Nephrops fishermen would be considerable. At the present time they catch large weight on deck and spend hours working through the catch for the large animals they want and discard the rest, dead. Hence an increase in mesh size to 70 mm in the Irish Sea and in the Celtic Sea would yield larger animals with less labour and catches of larger whiting which could be sold rather than discarded. A related problem is that of the hake. Hake were caught off Ireland and the west coast of Scotland by British fishermen who landed their catches predominantly in Milford Haven. During the late fifties and early sixties catches declined and now hake is not caught much by British 314
fishermen and the port of Milford has lost much of its fishing community. Part of the trouble was the efficient use of high headline trawls by French and Spanish fishermen, but another part was the exploitation of "needle" hake off the North coast of Spain and of very small hake by French Nephropstrawlers in La Grande Vasi~re. This is a mud bank off Brittany where the young hake grow up. A recent ICES Working Group has estimated that three quarters of the catch of hake in the Bay of Biscay is below the minimum landing size. Consequently the hake's exploitation pattern is being grossly abused. The "needle" hake fishery of long thin little fish is an old traditional one. That on La Grande Vasi~re is relatively new, having developed with the price of shrimp during the sixties. There is no reason why French Nephrops fishermen should not earn more money by catching larger shrimps with bigger mesh sizes because like their compatriots in the Irish and Celtic Seas they discard the bulk of their catches. An increase in mesh size in the Nephrops fishery and a reduction in the "needle" hake fishery would restore the hake stock and bring back potential catches to British fishermen. A further sample of a somewhat poor exploitation pattern is found in the mackerel fishery. Since about 1967 or so dense shoals of mackerel were found in Cornish waters in winter and catches increased there during the early seventies. When Russian and East European trawlers left European waters in 1977, very large catches were made by large British trawlers and were trans-shipped to Russian vessels. British catches off Cornwall and in the Minch have been in excess of 300 000 tons. In the Minch and on the Continental Shelf, the fish caught are large and old. Off Cornwall, however, a proportion of small fish is taken of between 25 cm and 30 cm in length. ICES has recommended that there be a closed area in Cornish waters in the western English Channel and in the Celtic Sea for much of the year; in other words fishing should be restricted to the midwinter period when the proportion of large fish is highest. Thus the exploitation pattern can be improved not only by increasing mesh sizes, but also by preventing the capture of small fish in a given area. Quite recently it has been shown that if the capture of small fish in Cornish waters were completely stopped (i.e. the area remained closed all the year round except for handliners and local trawlers) and if fishing were limited to the Continental Shelf and to the Minches, an extra 150 000 tons would be available to the fishermen. There is little danger that the mackerel stock would collapse in the immediate future because a strong year class is about to enter the fishery. However, if the present fishing mortality were sustained without a restraint on the capture of small fish in the Cornish area, the mackerel stock would collapse. This is the first time that fisheries biologists have been able to set down the conditions for collapse before it happens and it follows that the capture of small fish off Cornwall should be prevented because the alternative is to put between one third and one half of the international fishing fleet out of work (because there is little alternative employment). The capture of small fish should be eliminated in the North Sea demersal fisheries, in the hake fisheries and in the mackerel fishery. However, the improvement of exploitation pattern is only part of the conservation needed. The fishing mortality on cod, haddock and whiting in the North Sea is two to three times greater than it need be, even with a potential mesh size of 90 mm. Much the same is true
V o l u m e I l / N u m b e r I l / N o v e m b e r 1980
of the Arcto-Norwegian cod stock in the Barents Sea, of the sole stock in the North Sea and of cod and haddock stocks to the west of the British Isles. When the mesh size has reached its optimum size and the fishing mortality is still too high, catches must be reduced by quota or by effort regulation. In theory, effort regulation is the most desirable because fishing mortality is considered to be a direct function of fishing effort. This, however is very variable and statistics are lacking in many countries. When they declared a 200 mile limit, the Canadians cut foreign fishing effort by 40% and enforced it well, with the result that the cod stocks are recovering quickly. But this is a special case which does not apply to European waters from which the Russians and East Europeans have already been evicted. In European waters effort regulation on its own would be very difficult to manage. Total Allowable Catches (TACs) or catch quotas were introduced in ICNAF (International Commission for North West Atlantic Fisheries) in 1970 and into NEAFC (North East Atlantic Fisheries Commission) in 1974. Today all stocks of any value are under some sort of quota arrangements. In the absence of a Common Fisheries Policy, the EEC has not yet established quota regulations although quotas are published to which many, but not all, nations adhere. In the absence of quota regulation, the excess of catch over quota is always blamed on the foreigner. The fact that catches do not exceed quotas except in some well publicized instances is in itself evidence that fishing effort is much too high. But the next stage as consequence of
a Common Fisheries Policy must be the restriction of fishing by reduced quotas with monthly catch reporting. When quotas begin to bite with a system of enforcement linked to catch reports, there will be complaints, but they will be common and shared amongst fishermen of all nations. In The Fish Gate, published in 1943, Michael Graham stated the Great Law of Fishing, that free fishing becomes unprofitable. Therefore fishing effort has to be restrained in order that fishermen should make a living and that people can have steady supplies of fish at reasonable prices. One of the great dangers of management by the coastal state is that it could lead to overexploitation because most fish stock management has so far been international. There is no evidence yet that international management is to be preferred to that by the coastal state, but in European waters there is a very great opportunity to show that international management can be made to work. Not only do we need to control fishing effort by means of catch quota with monthly catch reporting, but the exploitation pattern needs to be improved in a number of fisheries. Michael Graham quotes the results of an experiment made at sea before the Second World War. Two ships were fishing alongside each other, one with the usual mesh of that period and the other with a slightly larger one; the larger mesh caught more large haddocks and fewer small ones and the trawler with the larger mesh earned slightly more. The fishermen's fears that an increase in mesh size will reduce their earnings are unjustified.
Marine Pollution Bulletin, Vol. I I, pp. 315-317
Pergamon Press Ltd. 1980.Printed in Great Britain
Pelagic Tar off Georgia and Florida m Relation to Physical Processes CAMILLE CORDES* LARRY ATKINSON,I- RICHARD LEE and JACK BLANTON
Skidway Institute of Oceanography, P.O. Box 13687, Savannah, Georgia31406, USA *Present address: S o u t h a m p t o n College, S o u t h a m p t o n , N e w York 11968, U S A t T o w h o m inquiries s h o u l d be a d d r e s s e d .
Following the Ixtoc I oil rig blowout in Campeche Bay we hypothesized that resulting tarballs should eventually appear in the Gulf Stream off Gerogia and that because of dynamic barriers in the innershelf little would reach nearshore areas. To test these hypotheses, surface tows to collect floating tar were taken off the coasts of Georgia and Florida in October and December, 1979. No tar was found within 40 km of the shore. All samples more than 40 km offshore contained some tar. The mean concentration was 0.82 mg m -2 with a range of 0.01-5.6 mg m -2. Closely spaced sampling showed extreme variation but trends were consistent. Perylene was the most abundant compound in the tarbails.
On 3 June 1979, the exploratory petroleum well Ixtoc I, located in Campeche Bay, Gulf of Mexico, experienced a blowout. More than 20 000 barrels per day of paraffin base crude oil spilled into the Gulf of Mexico. According to US Coast Guard sources, on 27 August 1979, heavy tarbaU concentrations were located about 120 miles southeast of Corpus Cristi. If the tar continued to travel with predominant currents, it would eventually be entrained in the Loop Current, exit the Gulf through the Straits of Florida and be advected north by the Gulf Stream. Levy & Walton (1976) define tarballs as oil which has been exposed to a variety of biological, chemical, physical and geological processes that alter its chemical composition 315