Statement of Senator Lisa A. Murkowski
Subcommittee on Fish, Wildlife & Water
Committee on Environment & Public Works
Hearing on Section 7 of the Endangered Species Act
Mr. Chairman, count me among those who believe the Section 7 consultation process needs major surgery.
Today’s witnesses will testify ably about the pros and cons of the Section 7 consultation process required by the Endangered Species Act, but will probably focus on experiences with freshwater or terrestrial species. But those are not the only areas where Section 7 comes into play.
Alaska’s fishing industry has recently had a very instructive encounter with the consultation process, which I would like to summarize for the record.
Steller sea lions, a marine mammal species, are managed by the National Marine Fisheries Service (NMFS). In 1975, the population in Alaska was estimated at more than 100,000 animals. By 1989, it had fallen to about 25,000. In 1990, Stellers were listed as threatened. In 1993, critical habitat was designated, and in 1997, the western population in the Aleutian Islands was declared to be “endangered.”
Under the Act, the status of the sea lion population triggered a section 7 consultation to consider the effects of fisheries. Since the fisheries are also managed by the National Marine Fisheries Service, this created the odd situation where the agency responsible for the fisheries was consulting with itself over its responsibility for the marine mammals.
From 1979 to 1998, NMFS repeatedly found that the fisheries did not adversely affect sea lions. But that wasn’t satisfactory to Greenpeace and other interests, which filed a lawsuit. After the lawsuit was filed, the agency suddenly reversed course. In late 1998, it issued a new biological opinion under section 7 which for the first time found “jeopardy” for the Alaska pollock fishery.
The finding was based on an untested theory popular among the agency’s marine mammal scientists, which supposed that fishing could cause localized depletion of pollock or disturb sea lion feeding patterns. Unfortunately, it ignored much of the available science, including evidence that largely exonerated fishing from blame for the sea lion decline, and demonstrated that sea lion stocks were healthiest where fishing activity was heaviest.
Despite that, it became the guiding principle for the agency, triggering five years of court battles, causing the agency to adopt “reasonable and prudent alternatives” which devastated whole communities dependent on fishing, and spawning two more biological opinions in an attempt to get the issue back on a reasonably even scientific keel.
What makes this case notable is not the outcome, but how badly the process itself was allowed to spin out of control, even though the National Marine Fisheries Service was both the agency conducting the action and the agency consulting on it.
Evidence that indicated fisheries were unlikely to harm sea lions was largely ignored. In 1989, again in 1994, and yet again in 1996, research by scientists looking for a link between pollock fishing and the sea lion decline had failed to yield the expected results. Although declines were found in some areas of heavy fishing, there were also sharp declines in areas with little or no fishing. Other scientists, publishing in 1991 and 1992, questioned the supposed link more directly. A 1991 paper by two of NMFS’ top fishery scientists actually seemed to indicate that there is an inverse relationship between pollock and sea lions. In fact, more recent work may even suggest that attempting to ensure less fishing and more pollock may have been the worst thing to do, because a pollock diet is less nutritious than one that includes fish of other species.
The failure of process in this case is that such a deeply questionable document as the 1998 biological opinion was accepted as gospel. Those responsible for overseeing the work failed to ensure that it was either justified or complete before it was accepted, and those who attempted to provide perspective on it were shut out of the process.
Worst of all, once such an error has been made, it may take many years and many dollars before it can be corrected.
Mr. Chairman, natural resource managers sometimes use the term “precautionary principle” to describe a better-safe-than-sorry approach to management. It should describe a reasonable effort to ensure that all information is considered and reasonable precautions are taken where there is uncertainty. It should not be an excuse for catering to the preconceived notion of one interest over another. The Section 7 process should be emblematic of the precautionary principle at its best, not at its worst.
Finally, Mr. Chairman, let me note that the National Marine Fisheries Service has, since the events I described, made a significant effort to improve its practices and prevent such abuses. That is laudable.
However, those efforts have been voluntary. The fact is that the potential for abuse remains inherent in the statute as it is currently written.
Conservation of species demands sound, objective science that examines all sides of an issue, not a subjective approach that caters to whims. To the extent that the law allows the latter to occur, it is at fault, and change is needed.
Mr. Chairman, I ask that I be allowed to place in the record a paper by Dr. Dayton L. Alverson, which discusses the scientific issues surrounding the Steller sea lion matter.
Thank you for undertaking to address this important issue, and for the opportunity to discuss an example of Alaska’s experience with the Section 7 process.
ATTACHMENT TO TESTIMONY
THE STELLER SEA LION AND POLLOCK
Perspective on Fisheries Interaction
DAYTON L. ALVERSON
At the onset of the 1990's there was a growing concern regarding the observed declines in the Steller sea lion (Eumetopias jubatus) throughout much of the North Pacific. A species of marine mammal whose population levels in the Kenai-to-Kiska region had reached levels exceeding 100thousand animals had declined from roughly 105thousand animals in 1975 to about 25,000 animals in 1989 (NMFS, 1992) Figure1.
The magnitude of the SSL decline led the National Marine Fisheries Service (NMFS) to declare SSL a threatened species in 1990, and later the western population endangered (1997), throughout much of the Gulf of Alaska and along the Aleutian Islands. With the listing of the SSL, NMFS became obligated by the Endangered Species Act to ensure that its proposed activities, including fisheries management, are not likely to jeopardize the continued existence of the SSL, or to result in the destruction or adverse modification of SSL "critical habitat."
NMFS is currently evaluating the potential impacts of pollock fisheries in the Gulf of Alaska and the Bering Sea, and particularly the proposed 1999 pollock management measures, on the western population of SSL, and on what NMFS has designated as "critical habitat" for SSL. In this evaluation, NMFS must consider whether the fisheries reasonably may be expected, directly or indirectly, to reduce appreciably the likelihood of both the survival and recovery of SSLs by reducing the reproduction, numbers, or distribution of the species. The effects of the pollock fisheries must be considered together with the effects of other activities that are interrelated or interdependent with the fishery. If NMFS were to conclude the pollock fishery is likely to jeopardize SSL, then NMFS must also consider how the adverse effects occur, as a precursor to considering whether the effects can be avoided through reasonable and prudent alternatives.
Initial Hypotheses For The Cause of SSL Decline Focused on Pollock Fisheries, But More Recent Work Suggests Causes Unrelated To The Fisheries.
In making a decision about jeopardy, NMFS must consider the "best available scientific and commercial data." A review of the available literature indicates that a variety of causes may be contributing to the decrease in SSL populations, and that the available data do not support the hypothesis that the pollock fishery is the cause of adverse effects to the SSL population.
Early views by many marine mammal scientists were that the expanded commercial fisheries, particularly in the Northeast Pacific for groundfish, were contributing to a food shortage for the SSL population. This argument, however, was called into question when it became apparent that the biomass of the dominant prey species, pollock, of the SSL during the 1980's trended upward and that more pollock rather than less was available to the SSL during its population decline.
Concurrently with NMFS' designation of the SSL as a threatened species, a number of hypotheses began to emerge regarding factors leading to the species population collapse. The NMFS Recovery Team (NMFS, 1992) identified 12 potential factors that were considered possible contributors to SSL declining population (Table 1), but it became increasingly apparent that most marine mammal scientists, close to the data, felt that malnutrition was a prime suspect.
During the late 1980's and early 1990's a variety of papers surfaced in scientific and gray literature noting the importance of pollock in the diet of SSL and the relationship between pollock and the commercial fisheries (see Fritz, et al., 1991; Loughlin and Merrick, 1989; Lowery, et al., 1989; Merrick, et al., 1987; Calkins, 1988; and Loughlin and Merrick, 1989). Although the issue of pollock in the diet of the SSL and the relationship between the commercial trawl fisheries as discussed by these authors differed, several major themes emerged from these early studies: (a)pollock was the major prey of sea lions and reference data included observation dating back prior to the decline in the SSL population; (b)the decline in the SSL could be associated with a significant growth in the commercial fisheries of the region; (c)the fisheries of the region caused a decline in the prey as the result of localized reductions in pollock abundance or fishing resulted in the fragmentation of pollock schools thus making it more difficult for SSL to feed; and (d)environmental factors were not considered a significant factor contributing to the SSL decline (Loughlin, 1987) Table1. Many of these views were embodied in the NMFS Sea Lion Recovery Team report of 1992.
The attempt to relate fishing activity to the decline in the SSL population dates well back into the 1980's when a number of papers focused on the heavy dependence of SSL on pollock in their diet (Trites, et al. in press). Efforts to associate the decline in SSL with fisheries soon became evident. In 1989, Loughlin and Merrick (1989) published a paper comparing sea lion counts and pollock catches for eight major rookeries and tested for time lagged effects. The results were perhaps surprising to the investigators in that few significant correlations were detected and they were both positive and negative. Later, Ferrero and Fritz (1994) tested the hypotheses that commercial catches of pollock were correlated with SSL abundance using additional rookeries and data collected after 1987 from the region between Kodiak Island and the Western Aleutian Islands. They too failed to find a relationship between the SSL abundance and pollock harvest using the available data. A third attempt, by Sampson (1996) found large winter catches of pollock occurred near sea lion rookeries that suffered large declines in the 1980's, but the report also showed sharp declines in SSLs in the late 1980's in areas where no winter catches of pollock had occurred. Sampson also was unable to relate the decline to the amount of fishing effort, total catches of groundfish, or catches of Pacific cod and Atka mackerel.
Nevertheless, the commentary and views of most marine mammal scientists remained largely unchallenged at the onset of the 1990's and the majority of those present at a workshop held in Anchorage, Alaska, (Alaska Sea Grant, 1991) came to the conclusion that lack of prey and nutrition was the most important factor contributing to the SSL decline. However, the Marasco and Aron (1991) paper on the character of changes in the Alaskan groundfish fisheries and a lengthy review of commercial fishing and the Steller sea lion by Alverson (1992) surfaced interesting questions suggesting alternative and broader interpretations of the decline of SSL populations.
The Marasco and Aron paper, which provided biomass data for pollock in the Bering Sea, made it obvious that the trends in pollock and SSL abundance were not directly related, in fact they appeared to be inversely related. Alverson (1992) suggested that: (1)available scientific evidence did not support the conclusion that pollock were important in the diet of SSL prior to the 1970's; (2)the possibility that the abundance of major forage items for sea lions shifted following the mid 1970's; (3)that prior to the significant growth of the pollock populations in the Bering Sea and Gulf of Alaska (during the 1970's) small fatty fish species such as capelin, sandlances and herring, probably formed the major elements of the diet of SSL throughout most of the Gulf of Alaska; (4)there was evidence (Wooster, personal comm.) of a major environmental shift in North Pacific ocean during the mid 1970's; and (5)that pollock were unlikely to provide the quality of nutrition that was provided by small fatty fish species. Alverson (1992) also suggested that an alternate hypothesis to the pollock commercial fishery interaction--that a loss of nutritional support for SSL had occurred as the result of the declining abundance of small forage species and the increased reliance on pollock, a species with low fat content.
Trites, et al. (1998) commenting on the relationship between the SSL and commercial fisheries puts a philosophical touch to the debate noting that there might appear to be superficial correlations between commercial fisheries and impacts on sea lion abundance However, as several authors have pointed out, life is never so simple. For example, sea lions are healthiest in southeast Alaska, an area that has the highest fishing vessel activity in the Gulf. Out in the Aleutians sea lion declines occurred at a time of little fishing activity. Recently Trites and his colleagues at the University of British Columbia (1998) noted (in reference to a NMFS management proposal) "we were surprised to learn that the leading hypothesis is lack of available prey." This hypothesis suggests that the SSL are starving to death; a statement that is not supported by field observations. The authors noted that if there is a relationship between SSL abundance it may be more subtle than gross statistics reveal.
In a news release from the Alaska Sea Grant program, researchers postulated that fishing is less a factor with respect to SSLs, because pollock stocks overall are high and the industry doesn't target young pollock. Dr. Jeremay Collie, a fishery researcher at the University of Alaska noted "in one sense, the findings exonerate the industry. We discussed pollock, but could only conclude that pollock stocks are up and sea lion are down."
It Is Highly Unlikely That Pollock Were An Important Item In The Diets Of SSLs During The Period Of SSL High Abundance.
The belief that pollock has traditionally been the dominate prey of the SSL seems to have gone through a rather radical shift during the past decade. Merrick, (1995) for example, confines his comments on data supporting the feeding pattern of SSL to the period of 1975 and forward, noting that these data constitute the only complete set available for comparison of temporal or area specific trends. Later Merrick (1995) provides evidence of a major shift in the availability of food for SSL, noting capelin abundance was high in the 1970's, but has since declined. Capelin also disappeared from seabird's diets in the Pribilof Islands and Gulf of Alaska beginning around 1978. Analysis of the pattern of scales deposition in sediment at Skan Bay on the north side of Unalaska (Eastern Aleutians) indicates that some small forage fish (myctophids and lumpsuckers) disappeared from the area in about 1978. The Bering Sea biomass of some other demersal species consumed by sea lions (sculpin and eelpouts) appear to have decreased from the late 1970's to the mid 1980's.
Dr. Michael Castellini, a marine mammal biologist at the University of Alaska, observed in the Alaska Sea Grant News (Alaska Sea Grant 1991) "there seems little doubt that [the decline of Stellers] is somehow related." The news report, however, goes on to say researchers " believe shortages of herring, capelin, sand lance, eulachon and other small forage fish favored as prey may have triggered the deaths of Steller sea lions and caused birth rates to drop." Castellini goes on to note "something has clearly changed in the environment and the consequences of these changes has been more pollock but fewer pollock of the age-classes preferred by sea lion."
Merrick, et al, (1997) noted that even during the period of decline there has been a significant shift in the diets of SSL. The occurrence of cod-like species in scats and stomachs from the declining sea lion population in the Kodiak Island area has increased from 32% in the 1976-1978 to 60% in 1985-1986. Small schooling fish occurrence decreased from 18% in 1975 to 6% in 1990-1993. Various authors have joined to support the hypothesis that a major change in the environment occurred in the mid 1970's resulting in a shift in the food supply for SSL (e.g., Alverson, 1992; Merrick, 1995; Boyd, 1995; NRC, 1996; Springer, in press; Pritcher, et al., in press). Pritcher, et al. (in press) for example concluded that there is strong evidence that a major oceanic regime shift, characterized by increased water temperature, began in the North Pacific, including the Gulf of Alaska, about 1975-1976. This regime shift apparently affected both biomass and composition of SSL prey with abrupt changes noted after 1978. Populations of small forage species such as capelin, eulachon, and Pacific sand fish declined greatly while larger, predator fishes such as walleye pollock and cod and flatfishes increased.
Boyd (1995) notes that major shifts in forage food available to the SSL have occurred during the period of the SSL decline, but the causes of these shifts are uncertain (and probably always will be), and may be due to (1)changes in the climatic/ oceanographic conditions, (2)stochastic or chaotic behavior in the main pathways of carbon flux, and (3)human intervention either through the removal of fish or sea lions or both. Some of the shifts in dominate forage species may have been fostered by climatic changes, harvesting of whales, herring, Pacific ocean perch or a combination of the above. Evidence that declines in SSL are related to groundfish or other fisheries of the region are weak, at best.
Recent Studies Increasingly Point To The Quality Of Prey,
Rather Than The Abundance Of Prey, As The Major Contributor To SSL Declines.
Trites, et al. (1998) noted that in discussing the relationship between the SSL and their decline there is a tendency to only emphasize the amount of individual fish species available to SSL or quantity removed from the environment. Little or no consideration is given to the diversity or quality of prey available to them. Pollock, the dominant prey currently available to SSL, are being consumed at the highest rates in the areas where the greatest SSL declines are noted. Further, these authors state that pollock are generally poor in energy or nutritional content. "They have about half the energy content as herring and have less usable energy due to various cost of digestion." According to Dr.David Rosen (UBC), during one trial, captive sea lions were fed exclusively on pollock and despite the fact that sea lions were fed essentially all the pollock they desired they actually lost body mass. "You're talking 16-18 kg in only two weeks. That's a major loss of weight for an animal that only weighs about 100 kg."
Merrick (1995) also raises the possibility of the nutritional problems associated with pollock, noting that diets of SSL in areas of the Aleutians, with the highest rates of population decline, had little diversity and were typically dominated by pollock. This was in sharp contrast to the observations of the diet of healthy SSL population in Southeast Alaska which included diversity of species including fatty fishes.
The debate over the effects of under-nutrition and its impacts on adults and young, at times, seem confusing and counterintuitive. For example, Merrick, et al., (1995) in a study comparing pup masses between rookeries and increasing and decreasing populations was surprised to find that the pup masses in the areas where populations were decreasing were significantly larger than those in areas with increasing populations. The large size of pups in the areas of decreasing populations suggest that pup condition was not compromised in the first months postpartum.. A reduced juvenile population implies that pregnant and early postpartum females in those populations are not having difficulty finding prey. It was also observed that the greater pup mass at the rookeries with reduced populations could be a density dependent response to reduced competition between females for food.
These findings seem somewhat at odds with results reported by Calkin, et al., (1998) who found that growth of female sea lions, as measured by standard length, auxiliary girth, and mass, was reduced between the 1970's and 1980's supporting the under-nutrition hypothesis. Pritcher, et al., (1998) in an investigation of pregnancy rates in females and under-nutrition concluded a significant decline had occurred between early and late (within year) pregnancy rates during the 1970's and 1980's (100% to 67% in the 1970's) and ( 95% to 55%) in the 1980's. The between-period decline was not significant, nevertheless, they concluded that there is considerable evidence suggesting nutritional stress affecting reproductive performance of the SSL during both 1970's and the 1980's. Additionally Calkins, et al., (1998) state "The findings of reduced body size between samples of SSL's collected in the mid 1970's and the mid 1980's seemingly indicate a reduced carrying capacity because of either a reduced abundance of or availability of prey and/or in prey composition to less nutritious species." In this case it would seem to indicate that carrying capacity declined even more rapidly than the population, but these authors note that a direct link has not been demonstrated between under-nutrition and the actual decline in numbers.
In regard to the nutritional hypothesis, Boyd (1995) concludes that "circumstantial evidence exist to suggest that changes in food availability could have been a cause of the decline, but that this may no longer be the main cause. Density-dependent responses, in terms of population size and the condition of pups, are possibly being observed amongst SSLs in the Eastern Aleutians. " Also with respect to pollock forming the dominate portion of food of SSLs, there is strong evidence which supports that pollock have constituted a significant percentage of their diet since the mid 1970's (Merrick, 1995). Prior to the early 1970's there is growing evidence that small forage species (herring, capelin, candlefish, and sandfish) were the key food items (Alverson, 1992; Merrick, 1995; Pritcher, et al. 1998). There is additional evidence that the shift to pollock during the late 1970's may have had the result of SSL opting for prey having much lower nutritional value than the small forage species which they had depended upon during years of high abundance (Trites, et al. 1998).
Pollock Fisheries Do Not Directly Compete With SSL for Pollock, And The Fisheries May Indirectly Increase The Portion Of The Pollock Population Targeted By SSL.
While research suggests the SSL are now reliant upon pollock as prey, the pollock fisheries and SSL are targeting different portions of the pollock population. Merrick and Calkins (1994), Merrick, et al. (1997) and other investigators have examined the importance of small, two year old and younger pollock, in the diet of SSL. The dominance of young fish in the examined stomachs seems well established. Merrick (1995) examined and found a relationship between the 1 and 2 year old pollock and the decline in SSL populations in the Eastern Aleutian Island area, but the trend in young fish prior to 1979 is not noted. However, Hallowed (1991) shows that the recruitment of age2 pollock increased more than 400% in the Gulf during this period, yet according to the Final Recovery Plan for the SSL (NMFS, 1991) the SSL population did not respond to the increase in young fish, but declined significantly. Merrick's data also can be used to show that although there was some decline in the numbers of 2year old pollock during the 1980's in the Gulf, the actual numbers of young pollock per surviving SSL increased 28%. Further, no supporting evidence has surfaced which suggest that the commercial fishery, which largely harvest 3-9 year old fish, has had any demonstrated impact on juvenile pollock abundance.
In a report currently under preparation by Consortium scientists (Trites personal comm.), ecosystem modeling failed to account for changes that occurred between 1950 and 1980 through trophic interactions alone. These scientists (Trites, personal comm.) concluded that "environmental change likely explains the build up of flatfish and the decline of pelagic fishes. Changes in the abundance of these key species can in turn affect the abundance of other species in the food web." Their model suggests that increased fishing pressure on pollock has a minimal affect on the adult biomass due to increased replenishment from the juvenile stock. Juvenile pollock benefit from reduced cannibalism and the model predicts that seals, sea lions and piscivorous birds would increase due to an increase in the abundance of juvenile pollock. According to the UBC consortium scientists, reducing the adult biomass 50% would have a positive affect on seals, sea lions and piscivorous birds because the abundance of juvenile pollock which they consume, increases as cannibalism by adult pollock is reduced. Reducing pollock fishing results in a larger adult population and a smaller juvenile pollock population.
Some in NMFS have suggested that trawling and sea lion foraging occurs at the same depths, which would increase the dispersive impact of trawling, even though the fishery targets larger fish than do SSL. (NMFS ESA public scoping session, 1998). However, it is apparent from data given by Merrick (1995) that the average diving depth of adult females and young of the year during the winter months is generally much shallower that the activities of trawlers fishing pollock during this time of the year. Merrick's work suggests that for SSLs that were tracked, "young of the year" made dives that were generally at depths of less than 16 fathoms (the mean diving depth was only 8.5 meters); far shallower than the winter trawl operations in the Gulf of Alaska and Bering Sea which fish at depths from 60 fathoms to over 100 fathoms. Adult winter female SSLs dive depths that are also relatively shallow in that a significant portion of the dives are less than 27 fathoms (the mean was 24 meters). It hardly seems likely that this feeding pattern would be disturbed by operating trawl fisheries.
Evidence Of Localized Depletion Of Pollock Stocks Is Equivocal At Best.
The failure to find convincing evidence that pollock abundance trends, in general, could be related to the SSL decline has resulted in the gradual abandonment of this hypothesis. NMFS has indicated that it does believe reductions in localized pollock populations may be occurring in SSL critical habitat (NMFS, ESA public scoping session, 1998). However, this preliminary conclusion does not appear to be supported by the best scientific data available.
There is little, if any, evidence that localized fishing within the year has led to negative impacts on the overall SSL population in the region where the species has been declared endangered. The works of Merrick, et. al, Fritz, Simpson, Trites and others who have examined this relationship have generally failed to establish a correlation.
The only new information discussing localized impacts of the pollock fishery on pollock stocks is NMFS data on pollock harvest in the Catcher Vessel Operating Area during the B season. This graphed and tabular data indicates a seasonal fishing harvest rate of 49% during the B season in 1997. However, the calculation of this harvest rate depends upon a number of doubtful underlying assumptions.
The harvest rate is calculated based on biomass removed during the harvest and the biomass distribution and quantity estimated from a trawl survey and hydroaccoustic data. There is an inference that the harvest rate and the remaining abundance of pollock may be equated, but this is not true. There was a 30 to 60 day lapse between when the survey data was collected and the time when the harvest estimate was made. This time lapse renders the attempt to correlate the two figures suspect, for several reasons.
First, the harvest rate was calculated assuming that there was no immigration or emigration from the region during and prior to the period of the survey. The time lapse renders that assumption unreasonable and necessarily qualifies the data. Second, independent of migration, there would have been additions to the population through recruitment and growth of the animals within the population during the same time lapse. The actual change in pollock abundance depends a great deal on the recruitment pattern during the lapse between the survey and the time fishing concluded in the B season.
This survey is, in any event, inadequate to demonstrate a localized depletion effect, as the rate of decline in the local pollock population is not the same as the local decline in the availability of prey to the SSL. These animals, to a significant extent, consume pollock that are not selected by the commercial fishery; that is, ages 0 - 2 years old. The rate of harvest for these age groups of pollock is not accounted for in the NMFS model or estimating procedure. For example, from length frequency data available from the fishery (only 1981 and 1985 data is available) it would appear that the fishery takes about 5% of its catch from animals below 26 cm and by weight probably less than 2% of the catch is made up of animals less than 3 years of age. Given that there is some overlap in the feeding of SSL, particularly in adult females, even if we take at face value that the overall localized reduction of the exploitable pollock biomass in 1997 during the B season was 49%, this would have had almost no impact on the size pollock eaten by young SSLs, and very little impact on the overall prey supply for adults. Finally, since pollock constitutes only a portion of the prey taken by the SSL population in the Catcher Vessel Operating Area and the critical habitat, the impacts are further minimized.
As NMFS has not provided an analysis of information available on the impact of fishing on prey available to SSL, nor considered recruitment and growth in other food components that may not be impacted at all by fishing, the 1997 B season data does not appear to provide NMFS with an adequate basis to form any conclusions regarding localized depletion of SSL prey as a result of fishing harvests.
Information on foraging trips studied by Merrick (1995) suggests that during the winter months, female and young animals make longer foraging trips and deeper dives. (Although not, per discussion above, to trawling depths.) The winter trips of the "young of the year," the animals generally considered at greatest risk, are for the most part less than 20 nm. The protracted trips seem to be taken by females during the winter, but there is no evidence that the longer trips are made in search of pollock. The long forage trips in the winter from Chirikof Island seem to be well beyond the continental shelf for lantern fish -- a fatty prey -- despite the fact that pollock was available much closer to the tagging sites.
Causes Other Than Prey Quality and Quantity Cannot Be Ruled Out.
Although a number of scientists appear to believe that nutritional problems may be at the heart of the SSL decline, very few write off other potential causes as contributing to the decline or being a part of a combination of factors contributing to the decline, whose importance has changed over time.
Boyd (1995) states "A range of proximate factors may have affected the decline. These include disease, disturbance, food availability (possibly mediated by changes in food chain structure), legal killing, (including subsistence harvest) predation, illegal killing and incidental catch. All these factors are likely to have affected the historical decline to different degrees and at different temporal and spatial scales. Only incidental killing in fisheries can now be excluded as a cause of the decline."
There is Increasing Evidence That SSL and Fisheries Do Not Compete Directly, And That The Fishery May Indirectly Benefit SSL.
The support for larger protective areas around rookeries (and haulout areas) flows, in part, from a conclusion that females and young sea lions in particular are having a difficult time foraging through the winter months. To the extent this may be true, it appears to result from a shift of the available food supply (starting in the mid-1970's) toward pollock as the result of a significant decline in the availability of forage species such as herring, sandlance, capelin, and other small bottom fish (Merrick, 1995; Alverson, 1992; Trites, et al., 1998 a and b; Pritcher, et al., in press; and NRC, 1996). Enlarging areas closed to trawling will not offset the loss of fatty prey fish from the SSL diet.
The success of a management action of this character (no trawl zones) will rest on the likelihood that: (1) the pollock fishery typically harvest pollock eaten by young SSLs or scatters the schools of pollock making them less accessible to young SSLs; and/or (2) there is a decline in the availability of young pollock to SSLs caused by the adjacent fisheries. But the pollock fishery targets age 3-9 fish, while young sea lions target age 2 and younger fish, and stable catch-per-unit-effort data suggests fishing is not dispersing the pollock. Thus, there is reason to doubt the likelihood of success of no trawl zones and similar measures designed to reduce or disburse the pollock catch.
Boyd (1995) notes "there have been substantial fisheries in areas designated as critical habitat for SSL, but unless the magnitude of these fisheries is expressed in terms of available biomass and there is an indication in the rate of flux of prey between critical and non-critical habitat, it is difficult to come to any conclusions about the potential impact of fisheries on sea lions even within the current exclusion zones. New research is required to examine the effects of changes in the rates at which sea lions encounter prey under different levels of fishing. There is a need for more information about fish behavior collected at the same spatial and temporal scales as data about sea lion behavior." Boyd further states that a strong precautionary principle should be adopted towards sea lion fisheries interactions, but notes, "there is support for the view that fisheries and sea lions do not compete directly since the fisheries are, in general, targeted at species or age classes that are not highly important in the diet of sea lions," concluding that "Our knowledge of the ecosystem processes is so rudimentary that such measures may have as much chance of being harmful as aiding recovery. " (Emphasis added.)
Springer (in press) concludes his paper on climate change by noting that "the role of climate as a force in population dynamics of species at higher trophic levels must be carefully weighed against the role of other factors, e.g., commercial fisheries, in setting management approaches that affect the lives of people and wildlife."
Trites, et al. (1998) in their comments on a NMFS proposal to more equally distribute the fishing for pollock in the Gulf of Alaska concluded that many of the statements made about SSLs and the impact of pollock fishing in the Federal Register are misleading. The potential problem in the SSL diet is not the lack of available prey, but rather the lack of appropriate prey. Exactly what constitutes appropriate prey is still under investigation. The effect of changing the timing of pollock harvest on SSL and therefore, changes in TAC and its allotment should be implemented cautiously. Given the current population decline, the results of the proposed changes in pollock management strategy are unpredictable and may produce unexpected and unwanted results.
Merrick (1995) discusses two possible interventions that could be considered to alter the decline in the SSL population. One would be to maintain high fishing effort on some species "emulate K-selected species and reduce variability in ecosystem biomass and the alternative to reduce fishing effort to allow stocks of Kspecies to rebuild." In the discussion of these options the author points out potential problems underlie both approaches and concludes that "what is clear is that the SSL probably will not recover unless a fundamental change occurs in the prey availability in the North Pacific Ocean."
In summary, it now appears that malnutrition is a prime suspect in the decline of western population of SSL. While research suggests that SSL are now reliant upon pollock as prey, available scientific evidence does not support the conclusion that pollock were important in the diet of SSL prior to the 1970's. Major shifts in forage food available to sea lions have occurred during the period of SSL decline. The commerical fisheries and SSL are targeting different portions of the pollock population. Any changes in the timing of pollock harvest should be approached with caution, since the results of such changes are unpredictable.
Alverson, Dayton L. 1992. A Review of Commercial Fisheries and the Steller Sea Lion (Eumetopias jubatus) the Conflict Arena. Rev. Aquat. Sci. 6:203-256.
Boyd I. L. 1995. Steller Sea Lion Research - A Report Prepared for the U. S. National Marine Fisheries Service, National Marine Mammal Laboratory, Seattle.
Calkins, D.G. and Goodwin. 1988. Investigation of the Declining Sea Lion Population in the Gulf of Alaska. Unpubl. Munuser. ADF&G.
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