- Email: [email protected]
Benthic baselines — A case for international collaboration
V¢lume9/Number 12/December1978
Round-the-World News Hong Kong A large new sewerage outfall pipe which will discharge treated sewage at the rate of 100000 cu.ft a day only a quarter of a mile from Middle Island has given rise to fears that beaches at Repulse Bay and Deep Water Bay will be polluted. But Public Works Department officials have given assurances that tidal current movements will dilute and disperse the sewage and prevent it being washed ashore.
Bacteriological Pollution Reports The Water Research Centre at Stevenage, England, has prepared two r e p o r t s - T R 77 and TR 7 9 - w h i c h detail work that followed extensive field studies on pollution in British coastal water (see TR 68). TR 77 outlines the principles and procedures of sampling seawater at a coastal site for subsequent bacteriological examination. TR 79 describes elementary statistical procedures used to analyse the results and discusses bacterial counts in sewage and river discharges. Norway Norwegian fishery researchers are concerned that the whole of the Norwegian-Arctic stock of cod is in serious jeopardy even though a number of fishing-free zones have been established in both the Russian and Norwegian sectors of the Barents Sea and around the Spitzbergen Archipelago. These no-fishing zones have been found inadequate for the protection of young cod stocks because of serious overfishing in adjoining areas. Since the introduction of the economic zones it is no longer possible for fishery inspection vessels to maintain strict control over such things as mesh sizes used by Russian
trawlers operating in the USSR zone and the researchers are recommending a return to the principle of reciprocal inspection rights at sea. Norway will also next year seek the introduction of a cod quota for waters around East Greenland.
Greece Conservationists have persuaded the Greek Government to drop a plan to create a massive industrial complex in Navarino Bay, an area of outstanding natural beauty in south-western Greece. Environmentalist groups took court action to prevent the industrial project which would have inevitably led to pollution from proposed steel mills, paint factories and cement plants. Now the area earmarked for the abandoned scheme- Pylos - is to be developed for tourism.
North America 35 major environmental organizations in Canada and the United States have formed a coalition called the CanadianUS Environmental Council (CUSEC). Formed originally to consider issues related to oil and gas development, the group meets annually to discuss issues ranging from pollution of the Great Lakes to river diversion programmes and power station siting proposals.
Japan The Japanese Environment Agency has warned that pesticides with organic sulphur content, if sprayed from aircraft in large amounts over forests near the sea, may pose a serious threat to marine life. The Agency prepared a report on the residual toxicity in the water of agricultural chemicals after reviewing the results of related studies conducted by Ministry of Agriculture experimental stations.
Marine Pollution Bulletin, Vol. 9, pp. 317-320 Pergamon Press l t d . 1978 Printed in Great Britain
l
Viewpoint is a column which allows authors to express their own opinions about current events.
Benthic Baselines- A Case for International Collaboration J. R. LEWIS
In an earlier 'Viewpoint' (Mar. Pollut. Bull., 9, 1978, 64) I contended that monitoring of benthic communities for pollution effects or conservation management purposes necessitates an ability to discount natural events. Not only does this presuppose an ability to recognise these events as such but also leads on to the desirable ecological aim of sufficient understanding for reliable prediction. I now consider further what may be involved in attaining these recognitive and predictive abilities.
Dr. Lewis is Director of the Weilcome Marine Laboratory of Leeds University at Robin Hood's Bay. We have first to recognise the potential natural sources of community change. These may be physical or biological, local or geographical in character or scale. Inevitably, local scale factors are best known, and on the physical side such things as cyclical or irregular changes in water movement, salinity, sediment content, substrate mobility and so on are all recognised as the obvious potential sources of natural community change that any judicious monitoring programme takes into account. Clearly, the more extreme a n d / o r 317
Marine Pollution Bulletin
unpredictable the physical changes and the greater the disturbance to the flora and fauna the less suitable such habitats and communities are for the detection of anything but catastrophic man-made effects. Where less severe or cyclical patterns of physical disturbance have been identified and studied for several years deviations from a regular pattern of re-colonisation might afford a measure of abnormal local water quality c o n d i t i o n s - always assuming constancy of other morewidely operating factors. Of considerably more intrinsic interest and practical significance are those less dramatic physical changes that are biologically induced. Since these may occur in ostensibly stable or relatively stable habitats the resulting biological changes could well be misinterpreted. Whatever the type of species involved (polychaetes, molluscs, echinoderms) or the way they modify the habitat, they give rise to the same questions: what density is needed to have this effect; how soon after colonisation; if density-dependent, what influences density in the first place; how soon can repopulation by the same species occur; must other phases with other species intervene and for how long. Given an initial awareness that such events may occur and thereafter, time for study, the possibility of misinterpretation can be minimised. Overlapping with the above but of more widespread significance because they are not necessarily associated with physical changes are the general biological interactions such as predation, grazing, spatial exclusion and so on. These and the succeeding repopulation process are the agencies continuously moulding the composition of communities. The temporal sequences are highly variable both between communities and within them, depending upon the type, size, life-spans, modes of feeding and of reproduction, and so forth of the component species. Within stable or cyclically predictable environments we could expect to find, depending upon the relative competitive a n d / o r recuperative efficiencies of the species involved, communities which at one extreme exhibit roughly cyclical patterns of change related to normal seasonal processes or to the duration of lifespans, through to others exhibiting the greater biological stability that is imposed by a long-lived or recurrently successful ecological dominant. Unless, in the latter condition, the dominant(s) is (are) much more tolerant of pollutants than the associate, subordinate or dependent species, that condition clearly presents the least problems. Where changes are frequent the problems are much greater but one can, nevertheless, and with time, still learn their types and timescales and acquire the ability to s a y - t h e abundance of species 'A' will effect species 'B' and 'C' t h u s - o r the presence of 'X' is usually followed by 'Y'. The accelerating study of community dynamics which now characterises benthic ecology has elucidated many such relationships. It still leaves many communities, particularly in the shallow subtidal, for which little is known about their structure and dynamic properties, the range and timescales of their entirely natural changes. But at least there can be no excuse now for ignoring the probability that such matters must be 318
considered. And as it becomes increasingly apparent that many species have wide physical tolerances and have their local abundance determined more by biological interactions, so one can understand that patchiness, with all its attendant practical and interpretational problems, can occur in a homogeneous, stable habitat simply because chance factors (e.g. passage of predator or grazers) cause interactions and re-population rates to be out of phase very locally. The methods of benthic s t u d y - v i s u a l on rock, by grab or cores in sediments-inevitably focus on this local scale to an extent that is rare in the pelagial sphere. And the more stable or predictable the environment (e.g. bedrock vs coarse sediment) the more the biological factors may emerge as the over-riding sources of the biological changes which have to be discounted as natural. To reach this level of awareness for more communities would be a great a d v a n c e - h e n c e my previous suggestion that we ascertain the prevalence and dynamics of communities with key species. But there remains another level of change to contend with, especially in the context of chronic pollution. If these detailed, local studies are pursued long enough and to sufficient depth we find that the biological processes and activities which lead to or constitute the interactions between species vary in intensity, not only seasonally as expected, but also irregularly on annual or longer timescales. Hence the r e c o g n i t i o n - p e r h a p s almost intuitive by an experienced n a t u r a l i s t - o f 'a good recruitment year', 'poor growth this season', 'a steady decline' and SO o n .
The first clue to identification of the cause of poor recruitment, poor growth (it is 'poor' not 'good' which usually causes concern!) would be the spatial extent of the event or change in question. Yet broadscale or distant 'controls' seldom figure in surveillance programmes. A wide geographical spread may still reflect the outcome of a biological chain action but the greater the scale the more likely is the event an ultimate result of physical factors which, to have transcended all local physical changes, must be climatic or hydrographic in character. When such conditions have departed strongly from the normal the biological consequences have been obvious (e.g. the heavy mortalities of coastal benthos in the severe winter of 1962/63), but even if such extreme cases are rare they should surely warn us that the lesser, more frequent variations will also be influencing the rates or directions of most biological processes or activities to some degree and thereby influencing communities at a very basic level. Whether or not such 'influences' become 'controls' depends upon matters other than the size of the abnormality, and so it is now appropriate to consider these probable geographic factors. In the larger estuaries, approaching or within large enclosed waters (e.g. the Baltic) the variations in their distinctive hydrographic regimes, felt perhaps over a large area, add a complicating and perhaps over-riding dimension; but elsewhere, along open coasts, with normal or near constant salinities the main environmental gradients are broadly related to latitude, i.e. sunlight, air and sea temperatures.
Volume9/Number 12/December1978 Along these latter, roughly N/S gradients (modified regionally by coastal orientation and topography and by currents) individual species have their respective northern and southern limits. Some species may be prevented from occupying their full potential range by competitors with different tolerances and greater efficiency, while others will persist up to the point where they succumb directly through intolerance at some stage in their life cycle. Either way adverse physical conditions are ultimately responsible; either way we can expect the actual geographical limits and nearby abundances to fluctuate appreciably as physical conditions vary from year to year. Moving from the edge to the centre of distribution, from limiting to suboptimal and then optimal conditions we may hypothesize that total competitive efficiency will increase, that scarcity or fluctuating abundance imposed primarily by physical factors will give way to abundances and greater overall stability which are probably regulated solely by local intra- and interspecific processes, i.e. density-independent factors give way to density-dependent. But will this be so for all species at all times? Stability is influenced by both life spans and re-population rates and obviously will be highest in communities comprising or dominated by long-lived, sedentary species. But many coastal life-spans are s h o r t - o r are made so by biological p r e s s u r e s - a n d annual recruitment rates, which if constantly high would compensate for this, are proving to be surprisingly variable, even well away from the distributional limit. Admittedly we have only a few long runs of reproductive or recruitment data in coastal benthos, but they indicate both a relationship to 'latitudinal f a c t o r s ' - a s indeed there must b e - a n d our general ignorance about the mode of operation. These irregular and perhaps unexpected recruitment v a r i a t i o n s - w h i c h may then have diverse community consequences - lead to speculative explanations. Perhaps reproductive and recruitment processes and stages are so very sensitive to direct physical factors that constancy is never attainable - but is it just one or a series of factors? Or could it be, since the northern and southern controls must be d i f f e r e n t - i n value if not in t y p e - a n d possibly affect different phases at different seasons, that annual variation in the latitudinal extent over which unrelated events are felt variously exposes species, even near the centre of their range, to one or the other, or to both or neither set of adverse conditions? Whatever direct effects may exist we have also to allow that the many trophic and competitive relationships affecting the different stages of a species life cycle inevitably change through its geographical range, and involve species which in turn are responding independently to perhaps a different series of physical or biological factors. Such speculations bring us face to face with what I regard as the major ecological challenges in coastal ecology. We have a good idea of local physical factors influencing local distribution; we are well on the way to documenting the scale of local biological interactions; we now need to know how physical factors set geographical limits and the extent and manner by which
these same factors influence or even control a b u n d a n c e - a n d thereby community d y n a m i c s - a t different parts of a species total range. The importance of such influence or control will doubtless vary, even within the same community. There will surely be instances when local physical disturbance or heavy predation far outweigh any possible community effect arising, for example, from increased growth by one or two species in response to higher sea temperatures. But one can also appreciate that whereas the conspicuous, very local elimination of a species (by a storm or severe predation) can soon be made good by immigrant larvae, a failure of gonad maturation in that species because of a slight temperature change would, because it would probably be a widespread event, have very significant and equally widespread consequences. Yet such a failure could pass unnoticed unless specifically investigated. This, it seems to me, is the type of predictive ability we have to aim f o r - seeking back into biological chains for the point at which measurable physical events or conditions impinge directly upon particular species with sufficient impact to entrain population and community changes. It is not enough to say, as previously, " t h e presence of 'A' will affect 'B' and 'C' thus"; we should ask why 'A' is or is not abundant in the first place. If this seems remote from 'pollution' it will be so only if a pollution effect is regarded as something discrete in itself, waiting to be studied and measured, rather than as it should be, something to be set in or deduced from a broad ecological perspective. Population and community changes and trends occurred before there was pollution, they are discernible today above the scale of local factor effects, and in some cases their direction is contrary to that expected from pollutant data. The case for more detailed investigation of these changes and their relationships with broadscale climatic/hydrographic factors is very strong. In the end the importance of such factors for the particular locality/habitat/community with which one is concerned may prove to be slight, but in practice a 'negative' outcome would greatly simplify future interpretation. There is only one way in which broadscale factors can be investigated: by equally wide-ranging study. But the regular and often simultaneous observation and measurement of certain vital activities or events throughout the geographical range of a particular species or community is beyond the capability of a single team, no matter how mobile it is. In view of the wide distributions usually involved the only practical solution is international collaboration in co-ordinated programmes using the same or intercalibrated methods. At each of a chain of stations along a continental coastline would be recorded not simply the numerical changes in communities but rather the extent to which particular species ('key' if they exist and are known) fluctuate as a result of their reproductive or recruitment success or from competitive or trophic influences at a later stage. From the broadscale biological patterns of such events from year to year, one would hope to obtain correlations with physical fluctuations, and then by progressive selection and intensification of field and laboratory studies to identify the most sensitive links in 319
Marine Pollution Bulletin
community control mechanisms in the different geographical regions. Although this is the ultimate ecological o b j e c t i v e - a n d may or may not be attainable in different c a s e s - t h e data required for this purpose are also very useful in an immediately practical way. Simply to know what is happening on a broad front would enable teams engaged upon intensive local studies to put some of their own local observations into perspective; if the local conforms to the general one can say, with or without understanding of the actual cause, that the event is probably natural. The choice of habitats and communities to be studied would depend on a concensus about their broadscale 'importance'. There would however be a need to avoid those which are subject to severe, unpredictable physical disturbance and, although not essential, there would be obvious initial advantages in selecting those for which there are already data and understanding about local physical influences and biological interactions. The stations would doubtless be influenced by the distribution of laboratories but would also have to take into
account anomalies or discontinuities in the climatic/ hydrographic gradients, and the separate geographical limits of individual key species. Littoral and coastal benthic ecology have traditionally been local in scale for both practical and financial r e a s o n s - p o o r man's marine biology for the most part yet not without its achievements. Fishery and plankton scientists on the other hand obtain their data from as wide an area as seems appropriate and it is now time to emulate them, the more so since both the variability of physical conditions and the likelihood of artificial stresses are greatest near to the shoreline. International collaboration in the way proposed benefits all participating countries yet shares the load. By thinking 'extensive' rather than 'expensive' the door to a new level of ecological understanding in benthic communities could be opened at reasonable cost. Indeed, with many teams now working on a proliferation of base-line/surveillance schemes there is surely much duplication already in the communities and species being studied. Does there also have to be isolation?
Marine Pollution Bulletin, Vol. 9, pp. 320 321 Pergamon Press l.td. 1978. Prinled in Great Britain
Fishing for Anchovies off California REUBEN LASKER
U.S. Dept. Commerce, NOAA, National Marine Fisheries Service, Southwest Fisheries Center, La Jolla, California, U.S.A. The recently adopted Anchovy Fishery Management Plan (Pacific Fishery Management Council [PFMC], 1978) mandated by the Fishery Conservation and Management Act of 1976 which established the 200-mile fishery zone for the United States, provides a formula for setting an annual optimum catch of the northern anchovy, Engraulis mordax, by U.S. and foreign fishermen off the California coast. Like the Peruvian anchoveta and the Atlantic menhaden, the northern anchovy is mostly reduced to fish meal and oil and provides an important protein supplement for poultry and other animal feeds. The last two triennial surveys for fish eggs and larvae (1975 and 1978) by the California Cooperative Oceanic Fisheries Investigations (CalCOFI) provided data from which spawning biomass estimates were made. They showed that there was a significant decline in the total anchovy spawning biomass over the 3-year period, from 3.3 million metric tons to 1.2 million metric tons. Natural variability in the size of the anchovy central stock is well documented and this spawning stock size, 1.2 m tons, was last recorded in 1961 (PFMC, 1978). Information obtained from the fishery showed that the 1974 and 1975 year classes were very poor and 320
contributed to the decline in the whole anchovy population, although the 1976 year class was better than average. Until 1978, fishing on the anchovy was regulated by the Fish and Game Commission of the State of California and was held to a modest take, approximately 163 000 tons in 1975. With the advent of an unregulated Mexican fishery on the same stock south of the border, the 1977 catch totalled approximately 257000 tons (Mexico, 157000; U.S., 100000). A combination of heavy fishing on the spawning stock with the coincidence of a number of successively poor year classes has depressed other clupeoid stocks (Murphy, 1977). Whether a 257000 ton fishery can be considered to be 'heavy fishing' is unknown for this stock, but the Anchovy Plan would have restricted this much fishing if the spawning biomass had been known to be low for 1977; no assessment cruise was made in 1977, nor was the plan in effect at that time. So far Mexico has not adopted the U.S. plan, and fishes this stock without restriction. While fishing can be regulated in each country by political means, the causes of natural fluctuations in population size remain largely unknown although the so-called 'stock and recruitment problem' is an active area of research throughout the world.
Round-the-World News Hong Kong A large new sewerage outfall pipe which will discharge treated sewage at the rate of 100000 cu.ft a day only a quarter of a mile from Middle Island has given rise to fears that beaches at Repulse Bay and Deep Water Bay will be polluted. But Public Works Department officials have given assurances that tidal current movements will dilute and disperse the sewage and prevent it being washed ashore.
Bacteriological Pollution Reports The Water Research Centre at Stevenage, England, has prepared two r e p o r t s - T R 77 and TR 7 9 - w h i c h detail work that followed extensive field studies on pollution in British coastal water (see TR 68). TR 77 outlines the principles and procedures of sampling seawater at a coastal site for subsequent bacteriological examination. TR 79 describes elementary statistical procedures used to analyse the results and discusses bacterial counts in sewage and river discharges. Norway Norwegian fishery researchers are concerned that the whole of the Norwegian-Arctic stock of cod is in serious jeopardy even though a number of fishing-free zones have been established in both the Russian and Norwegian sectors of the Barents Sea and around the Spitzbergen Archipelago. These no-fishing zones have been found inadequate for the protection of young cod stocks because of serious overfishing in adjoining areas. Since the introduction of the economic zones it is no longer possible for fishery inspection vessels to maintain strict control over such things as mesh sizes used by Russian
trawlers operating in the USSR zone and the researchers are recommending a return to the principle of reciprocal inspection rights at sea. Norway will also next year seek the introduction of a cod quota for waters around East Greenland.
Greece Conservationists have persuaded the Greek Government to drop a plan to create a massive industrial complex in Navarino Bay, an area of outstanding natural beauty in south-western Greece. Environmentalist groups took court action to prevent the industrial project which would have inevitably led to pollution from proposed steel mills, paint factories and cement plants. Now the area earmarked for the abandoned scheme- Pylos - is to be developed for tourism.
North America 35 major environmental organizations in Canada and the United States have formed a coalition called the CanadianUS Environmental Council (CUSEC). Formed originally to consider issues related to oil and gas development, the group meets annually to discuss issues ranging from pollution of the Great Lakes to river diversion programmes and power station siting proposals.
Japan The Japanese Environment Agency has warned that pesticides with organic sulphur content, if sprayed from aircraft in large amounts over forests near the sea, may pose a serious threat to marine life. The Agency prepared a report on the residual toxicity in the water of agricultural chemicals after reviewing the results of related studies conducted by Ministry of Agriculture experimental stations.
Marine Pollution Bulletin, Vol. 9, pp. 317-320 Pergamon Press l t d . 1978 Printed in Great Britain
l
Viewpoint is a column which allows authors to express their own opinions about current events.
Benthic Baselines- A Case for International Collaboration J. R. LEWIS
In an earlier 'Viewpoint' (Mar. Pollut. Bull., 9, 1978, 64) I contended that monitoring of benthic communities for pollution effects or conservation management purposes necessitates an ability to discount natural events. Not only does this presuppose an ability to recognise these events as such but also leads on to the desirable ecological aim of sufficient understanding for reliable prediction. I now consider further what may be involved in attaining these recognitive and predictive abilities.
Dr. Lewis is Director of the Weilcome Marine Laboratory of Leeds University at Robin Hood's Bay. We have first to recognise the potential natural sources of community change. These may be physical or biological, local or geographical in character or scale. Inevitably, local scale factors are best known, and on the physical side such things as cyclical or irregular changes in water movement, salinity, sediment content, substrate mobility and so on are all recognised as the obvious potential sources of natural community change that any judicious monitoring programme takes into account. Clearly, the more extreme a n d / o r 317
Marine Pollution Bulletin
unpredictable the physical changes and the greater the disturbance to the flora and fauna the less suitable such habitats and communities are for the detection of anything but catastrophic man-made effects. Where less severe or cyclical patterns of physical disturbance have been identified and studied for several years deviations from a regular pattern of re-colonisation might afford a measure of abnormal local water quality c o n d i t i o n s - always assuming constancy of other morewidely operating factors. Of considerably more intrinsic interest and practical significance are those less dramatic physical changes that are biologically induced. Since these may occur in ostensibly stable or relatively stable habitats the resulting biological changes could well be misinterpreted. Whatever the type of species involved (polychaetes, molluscs, echinoderms) or the way they modify the habitat, they give rise to the same questions: what density is needed to have this effect; how soon after colonisation; if density-dependent, what influences density in the first place; how soon can repopulation by the same species occur; must other phases with other species intervene and for how long. Given an initial awareness that such events may occur and thereafter, time for study, the possibility of misinterpretation can be minimised. Overlapping with the above but of more widespread significance because they are not necessarily associated with physical changes are the general biological interactions such as predation, grazing, spatial exclusion and so on. These and the succeeding repopulation process are the agencies continuously moulding the composition of communities. The temporal sequences are highly variable both between communities and within them, depending upon the type, size, life-spans, modes of feeding and of reproduction, and so forth of the component species. Within stable or cyclically predictable environments we could expect to find, depending upon the relative competitive a n d / o r recuperative efficiencies of the species involved, communities which at one extreme exhibit roughly cyclical patterns of change related to normal seasonal processes or to the duration of lifespans, through to others exhibiting the greater biological stability that is imposed by a long-lived or recurrently successful ecological dominant. Unless, in the latter condition, the dominant(s) is (are) much more tolerant of pollutants than the associate, subordinate or dependent species, that condition clearly presents the least problems. Where changes are frequent the problems are much greater but one can, nevertheless, and with time, still learn their types and timescales and acquire the ability to s a y - t h e abundance of species 'A' will effect species 'B' and 'C' t h u s - o r the presence of 'X' is usually followed by 'Y'. The accelerating study of community dynamics which now characterises benthic ecology has elucidated many such relationships. It still leaves many communities, particularly in the shallow subtidal, for which little is known about their structure and dynamic properties, the range and timescales of their entirely natural changes. But at least there can be no excuse now for ignoring the probability that such matters must be 318
considered. And as it becomes increasingly apparent that many species have wide physical tolerances and have their local abundance determined more by biological interactions, so one can understand that patchiness, with all its attendant practical and interpretational problems, can occur in a homogeneous, stable habitat simply because chance factors (e.g. passage of predator or grazers) cause interactions and re-population rates to be out of phase very locally. The methods of benthic s t u d y - v i s u a l on rock, by grab or cores in sediments-inevitably focus on this local scale to an extent that is rare in the pelagial sphere. And the more stable or predictable the environment (e.g. bedrock vs coarse sediment) the more the biological factors may emerge as the over-riding sources of the biological changes which have to be discounted as natural. To reach this level of awareness for more communities would be a great a d v a n c e - h e n c e my previous suggestion that we ascertain the prevalence and dynamics of communities with key species. But there remains another level of change to contend with, especially in the context of chronic pollution. If these detailed, local studies are pursued long enough and to sufficient depth we find that the biological processes and activities which lead to or constitute the interactions between species vary in intensity, not only seasonally as expected, but also irregularly on annual or longer timescales. Hence the r e c o g n i t i o n - p e r h a p s almost intuitive by an experienced n a t u r a l i s t - o f 'a good recruitment year', 'poor growth this season', 'a steady decline' and SO o n .
The first clue to identification of the cause of poor recruitment, poor growth (it is 'poor' not 'good' which usually causes concern!) would be the spatial extent of the event or change in question. Yet broadscale or distant 'controls' seldom figure in surveillance programmes. A wide geographical spread may still reflect the outcome of a biological chain action but the greater the scale the more likely is the event an ultimate result of physical factors which, to have transcended all local physical changes, must be climatic or hydrographic in character. When such conditions have departed strongly from the normal the biological consequences have been obvious (e.g. the heavy mortalities of coastal benthos in the severe winter of 1962/63), but even if such extreme cases are rare they should surely warn us that the lesser, more frequent variations will also be influencing the rates or directions of most biological processes or activities to some degree and thereby influencing communities at a very basic level. Whether or not such 'influences' become 'controls' depends upon matters other than the size of the abnormality, and so it is now appropriate to consider these probable geographic factors. In the larger estuaries, approaching or within large enclosed waters (e.g. the Baltic) the variations in their distinctive hydrographic regimes, felt perhaps over a large area, add a complicating and perhaps over-riding dimension; but elsewhere, along open coasts, with normal or near constant salinities the main environmental gradients are broadly related to latitude, i.e. sunlight, air and sea temperatures.
Volume9/Number 12/December1978 Along these latter, roughly N/S gradients (modified regionally by coastal orientation and topography and by currents) individual species have their respective northern and southern limits. Some species may be prevented from occupying their full potential range by competitors with different tolerances and greater efficiency, while others will persist up to the point where they succumb directly through intolerance at some stage in their life cycle. Either way adverse physical conditions are ultimately responsible; either way we can expect the actual geographical limits and nearby abundances to fluctuate appreciably as physical conditions vary from year to year. Moving from the edge to the centre of distribution, from limiting to suboptimal and then optimal conditions we may hypothesize that total competitive efficiency will increase, that scarcity or fluctuating abundance imposed primarily by physical factors will give way to abundances and greater overall stability which are probably regulated solely by local intra- and interspecific processes, i.e. density-independent factors give way to density-dependent. But will this be so for all species at all times? Stability is influenced by both life spans and re-population rates and obviously will be highest in communities comprising or dominated by long-lived, sedentary species. But many coastal life-spans are s h o r t - o r are made so by biological p r e s s u r e s - a n d annual recruitment rates, which if constantly high would compensate for this, are proving to be surprisingly variable, even well away from the distributional limit. Admittedly we have only a few long runs of reproductive or recruitment data in coastal benthos, but they indicate both a relationship to 'latitudinal f a c t o r s ' - a s indeed there must b e - a n d our general ignorance about the mode of operation. These irregular and perhaps unexpected recruitment v a r i a t i o n s - w h i c h may then have diverse community consequences - lead to speculative explanations. Perhaps reproductive and recruitment processes and stages are so very sensitive to direct physical factors that constancy is never attainable - but is it just one or a series of factors? Or could it be, since the northern and southern controls must be d i f f e r e n t - i n value if not in t y p e - a n d possibly affect different phases at different seasons, that annual variation in the latitudinal extent over which unrelated events are felt variously exposes species, even near the centre of their range, to one or the other, or to both or neither set of adverse conditions? Whatever direct effects may exist we have also to allow that the many trophic and competitive relationships affecting the different stages of a species life cycle inevitably change through its geographical range, and involve species which in turn are responding independently to perhaps a different series of physical or biological factors. Such speculations bring us face to face with what I regard as the major ecological challenges in coastal ecology. We have a good idea of local physical factors influencing local distribution; we are well on the way to documenting the scale of local biological interactions; we now need to know how physical factors set geographical limits and the extent and manner by which
these same factors influence or even control a b u n d a n c e - a n d thereby community d y n a m i c s - a t different parts of a species total range. The importance of such influence or control will doubtless vary, even within the same community. There will surely be instances when local physical disturbance or heavy predation far outweigh any possible community effect arising, for example, from increased growth by one or two species in response to higher sea temperatures. But one can also appreciate that whereas the conspicuous, very local elimination of a species (by a storm or severe predation) can soon be made good by immigrant larvae, a failure of gonad maturation in that species because of a slight temperature change would, because it would probably be a widespread event, have very significant and equally widespread consequences. Yet such a failure could pass unnoticed unless specifically investigated. This, it seems to me, is the type of predictive ability we have to aim f o r - seeking back into biological chains for the point at which measurable physical events or conditions impinge directly upon particular species with sufficient impact to entrain population and community changes. It is not enough to say, as previously, " t h e presence of 'A' will affect 'B' and 'C' thus"; we should ask why 'A' is or is not abundant in the first place. If this seems remote from 'pollution' it will be so only if a pollution effect is regarded as something discrete in itself, waiting to be studied and measured, rather than as it should be, something to be set in or deduced from a broad ecological perspective. Population and community changes and trends occurred before there was pollution, they are discernible today above the scale of local factor effects, and in some cases their direction is contrary to that expected from pollutant data. The case for more detailed investigation of these changes and their relationships with broadscale climatic/hydrographic factors is very strong. In the end the importance of such factors for the particular locality/habitat/community with which one is concerned may prove to be slight, but in practice a 'negative' outcome would greatly simplify future interpretation. There is only one way in which broadscale factors can be investigated: by equally wide-ranging study. But the regular and often simultaneous observation and measurement of certain vital activities or events throughout the geographical range of a particular species or community is beyond the capability of a single team, no matter how mobile it is. In view of the wide distributions usually involved the only practical solution is international collaboration in co-ordinated programmes using the same or intercalibrated methods. At each of a chain of stations along a continental coastline would be recorded not simply the numerical changes in communities but rather the extent to which particular species ('key' if they exist and are known) fluctuate as a result of their reproductive or recruitment success or from competitive or trophic influences at a later stage. From the broadscale biological patterns of such events from year to year, one would hope to obtain correlations with physical fluctuations, and then by progressive selection and intensification of field and laboratory studies to identify the most sensitive links in 319
Marine Pollution Bulletin
community control mechanisms in the different geographical regions. Although this is the ultimate ecological o b j e c t i v e - a n d may or may not be attainable in different c a s e s - t h e data required for this purpose are also very useful in an immediately practical way. Simply to know what is happening on a broad front would enable teams engaged upon intensive local studies to put some of their own local observations into perspective; if the local conforms to the general one can say, with or without understanding of the actual cause, that the event is probably natural. The choice of habitats and communities to be studied would depend on a concensus about their broadscale 'importance'. There would however be a need to avoid those which are subject to severe, unpredictable physical disturbance and, although not essential, there would be obvious initial advantages in selecting those for which there are already data and understanding about local physical influences and biological interactions. The stations would doubtless be influenced by the distribution of laboratories but would also have to take into
account anomalies or discontinuities in the climatic/ hydrographic gradients, and the separate geographical limits of individual key species. Littoral and coastal benthic ecology have traditionally been local in scale for both practical and financial r e a s o n s - p o o r man's marine biology for the most part yet not without its achievements. Fishery and plankton scientists on the other hand obtain their data from as wide an area as seems appropriate and it is now time to emulate them, the more so since both the variability of physical conditions and the likelihood of artificial stresses are greatest near to the shoreline. International collaboration in the way proposed benefits all participating countries yet shares the load. By thinking 'extensive' rather than 'expensive' the door to a new level of ecological understanding in benthic communities could be opened at reasonable cost. Indeed, with many teams now working on a proliferation of base-line/surveillance schemes there is surely much duplication already in the communities and species being studied. Does there also have to be isolation?
Marine Pollution Bulletin, Vol. 9, pp. 320 321 Pergamon Press l.td. 1978. Prinled in Great Britain
Fishing for Anchovies off California REUBEN LASKER
U.S. Dept. Commerce, NOAA, National Marine Fisheries Service, Southwest Fisheries Center, La Jolla, California, U.S.A. The recently adopted Anchovy Fishery Management Plan (Pacific Fishery Management Council [PFMC], 1978) mandated by the Fishery Conservation and Management Act of 1976 which established the 200-mile fishery zone for the United States, provides a formula for setting an annual optimum catch of the northern anchovy, Engraulis mordax, by U.S. and foreign fishermen off the California coast. Like the Peruvian anchoveta and the Atlantic menhaden, the northern anchovy is mostly reduced to fish meal and oil and provides an important protein supplement for poultry and other animal feeds. The last two triennial surveys for fish eggs and larvae (1975 and 1978) by the California Cooperative Oceanic Fisheries Investigations (CalCOFI) provided data from which spawning biomass estimates were made. They showed that there was a significant decline in the total anchovy spawning biomass over the 3-year period, from 3.3 million metric tons to 1.2 million metric tons. Natural variability in the size of the anchovy central stock is well documented and this spawning stock size, 1.2 m tons, was last recorded in 1961 (PFMC, 1978). Information obtained from the fishery showed that the 1974 and 1975 year classes were very poor and 320
contributed to the decline in the whole anchovy population, although the 1976 year class was better than average. Until 1978, fishing on the anchovy was regulated by the Fish and Game Commission of the State of California and was held to a modest take, approximately 163 000 tons in 1975. With the advent of an unregulated Mexican fishery on the same stock south of the border, the 1977 catch totalled approximately 257000 tons (Mexico, 157000; U.S., 100000). A combination of heavy fishing on the spawning stock with the coincidence of a number of successively poor year classes has depressed other clupeoid stocks (Murphy, 1977). Whether a 257000 ton fishery can be considered to be 'heavy fishing' is unknown for this stock, but the Anchovy Plan would have restricted this much fishing if the spawning biomass had been known to be low for 1977; no assessment cruise was made in 1977, nor was the plan in effect at that time. So far Mexico has not adopted the U.S. plan, and fishes this stock without restriction. While fishing can be regulated in each country by political means, the causes of natural fluctuations in population size remain largely unknown although the so-called 'stock and recruitment problem' is an active area of research throughout the world.