The Threatened Status of Steller Sea Lions, Eumetopias jubatus, under the Endangered Species Act: Effects on Alaska Groundfish Fisheries Management
LOWELL W. FRITZ, RICHARD C. FERRERO and RONALD J. BERG
Introduction altered fishery resource management in listed under the ESA were large ceta the Gulf of Alaska, Bering Sea, and ceans. These animals were among the During the 1970's, the U.S. Congress Aleutian Islands regions. In 1976, the first to be listed in 1973 after nearly two passed legislation which significantly Magnuson Fishery Conservation and centuries of commercial whaling sig Management Act (MFCMA) instituted nificantly reduced their populations. Lowell W. Fritz and Richard C. Ferrero are with a fishery management system under The majority of these harvests occurred the Alaska Fisheries Science Center, National NOAA's National Marine Fisheries Ser outside of Alaska waters. In contrast, Marine Fisheries Service, NOAA, 7600 Sand Point Way N.E., Seattle, WA 98115, and Ronald vice (NMFS) and established the North the Steller sea lion listing addressed a J. Berg is with the Alaska Regional Office, Na Pacific Fisheries Management Council more recent phenomenon, and it was tional Marine Fisheries Service, NOAA, Federal Building, 709 West 9th St., Juneau, AK 98802. (NPFMC). Earlier, the Marine Mammal prompted by studies in the 1970's and This paper was presented at a symposium entitled Protection Act (MMPA) of 1972 ad 1980's that revealed major declines in "Fisheries Management: Global Trends," June dressed the diminished status of many abundance in the core of the species' 1994, held in Seattle, Wash., which was spon soredjointly by the University ofWashington and marine mammal populations and intro range (Fig. 1) (Braham et a!., 1980; the National Marine Fisheries Service. duced mechanisms to limit their mortal Merrick et a!., 1987; Loughlin et a!., ity in commercial fisheries operating in 1992) and a deterioration in individual ABSTRACT-In April 1990, the Steller side the u.s. 3-200 n.mi. Exclusive Eco condition (Calkins and Goodwin l ). For sea lion, Eumetopias jubatus, was listed as nomic Zone (EEZ). And in 1973, the En the first time under the ESA, a coastal threatened under the U.S. Endangered Spe cies Act by emergency action. Competitive dangered Species Act (ESA) established piscivorous marine mammal was listed interactions with the billion-dollar Alaska rules to protect species considered to be which had both a history of high inci commercial groundfish fisheries have been threatened with or in danger ofextinction. dental takes by fisheries and an overlap suggested as one ofthe possible contribut Even as the MFCMA shaped the in diet and distribution with those fish ing factors to the Steller sea lion popula tion decline. Since the listing, fisheries man character of U.S. fisheries, the MMPA eries (Calkins and Pitcher, 1982; Loughlin agers have attempted to address the poten and particularly the ESA influenced and Nelson, 1986; Perez and Loughlin, tial impacts of the groundfish fisheries on fisheries management where interac 1991; Calkins and Goodwin l ). Steller sea lion recovery. In this paper, we tions with marine mammals occur. This The listing of Steller sea lions as a review pertinent Federal legislation, bio broadened attention to potential rela threatened species created new chal logical information on the Steller sea lion decline, changes in the Alaska trawl fish tionships between commercial fisheries lenges for fisheries managers needing ery for walleye pollock, Theragra chalco and marine mammals was evident in the to balance the conservation and recov gramma, since the late 1970's, andpossible Alaska groundfish fisheries after the ery requirements of the ESA for Steller interactions betweenfisheries andsea lions. NMFS listed the Steller sea lion, sea lions with the needs of the Alaska Using three cases, we illustrate how the list ing of Steller sea lions has affected Alaska Eumetopias jubatus, as a threatened groundfish fishery, one of the largest groundfish fisheries through: I) actions taken species under the ESA (5 April 1990; fisheries in the world. This paper ex at the time oflisting designed to limit the po 55 FR 12645). The Steller sea lion list amines how the threatened status of the tentialfor direct human-related sea lion mor ing has been an important factor in the Steller sea lion has affected groundfish tality, 2) actions addressing spatial and tem recent evolution in North Pacific fisheries management off Alaska using poral separation offisheries from sea lions, and 3) introduction of risk-adverse stock as groundfish fisheries management and three examples of management actions sessment methodologies and Steller sea lion has heightened awareness of the impact from the time of listing to the present. conservation considerations directly in the fisheries may have on marine ecosys annual quota-setting process. This discussion tems in general and on nontarget, I Calkins, D., and E. Goodwin. 1988. Investiga shows some of the ways that North Pacific nonfish species in particular. tion of the declining sea lion population in the groundfish resource managers have begun to Gulf of Alaska. Rep. Alaska Dep. Fish Game, explicitly consider the conservation ofmarine Prior to 1990, the only marine mam 333 Raspberry Road, Anchorage, AK 99518 mammal and other nontarget species. mal species inhabiting Alaska waters 1599,76 p.
14 Marine Fisheries Review These actions are placed in context by between Steller sea lions and commer The NPFMC receives advice from a first reviewing 1) the legal and manage cial groundfish fisheries. Scientific and Statistical Committee ment framework under which Alaska (SSC) on the acceptable biological Legal and Management Framework groundfish fisheries are managed, 2) the catch (ABC) and overfishing level for recent history of the largest fishery off each target species, and an Advisory Magnuson Fisheries Conservation Alaska, the trawl fishery for walleye Panel (AP) of industry representatives and Management Act pollock, Theragra chalcogramma, 3) on the total allowable catch (TAC) based possible causes of the decline in the The primary objective of the MFCMA on economic and social concerns. The Steller sea lion population in Alaska, is to conserve and manage U.S. fishery ABC's are initially determined by stock and 4) the nature of the interactions resources for sustained human use. To assessment scientists and reviewed by achieve this goal, regional fishery man separate Bering Sea and Aleutian Is 120,000 '"c agement councils (e.g., the NPFMC) lands (BSAI) region and Gulf ofAlaska ~ 100,000 were established to manage fisheries (GOA) Plan Teams. The ABC's have '"Q) 80,000 inside the U.S. EEZ. Councils manage generally been developed using single ~'" 60,000 fisheries through development of fish ~ species stock assessment philosophies '0 40,000 ery management plans (FMP's) which (e.g., Pope, 1972; Deriso et aI., 1985; Q; .c outline how optimum yields will be Methot, 1990; Clark, 1991) which § 20,000 2 Z achieved while preventing overfishing. maximize yield while preventing over 0 55 65 75 85 Management councils are composed of fishing of each species, but do not ex Year representatives of Federal and state plicitly account for trophic interactions Figure L - Number of adult and juve agencies as well as the private sector. with other taxa. nile Steller sea lions counted on trend rookeries and haul outs from the Kenai 2 Groundfish fisheries off Alaska are managed Marine Mammal Protection Act Peninsula (long, 1500 W) to Kiska Island by two FMP's covering I) the Gulf of Alaska (long, 177°E), Alaska, during 7 surveys (GOA; the southern coast to long. 1700 W), and The purpose of the MMPA is to pro conducted from 1957 to 1992, 2) the Bering Sea/Aleutian Islands (BSAI). vide protection for marine mammals so
Steller sea lions, Eumetopias jubatus,
57(2),1995 15 that their populations are maintained as establish teams of experts in marine tat is broadly defined as "the specific significant, functioning elements of a mammal conservation and biology and areas ... essential to the conservation healthy marine ecosystem. The MMPA fishing practices that will develop plans of the species and which may require placed a moratorium on the take (i.e., to reduce the levels of incidental take special management consideration or harassment, hunt, capture, or kill) and of strategic stocks in fisheries. The 1994 protection." As discussed below with importation of marine mammals, but amendments retain the zero mortality respect to Section 7 of the ESA, the ar contained provisions for limited takes rate goal for marine mammals in fish eas designated as critical habitat can in the course of commercial fishing eries and specify that all fisheries must have important management implica operations. Although the ultimate goal attain that goal within seven years. tions: Federal agencies proposing ac was to reduce takes to negligible lev tions within critical habitat must ensure Endangered Species Act els, two mechanisms were established that their actions are not likely to de for allowing some incidental take: gen The goals of the ESA are to prevent stroy those features which make it eral permits and small take exemptions the extinction of species, to encourage "critical" nor adversely modify its use (added to the MMPA in 1981). The recovery of listed species to the point fulness to the listed species. Designa former mechanism allowed large num that they no longer need protection, and tion of critical habitat by itself, how bers of a species to be taken if it was at to preserve their ecosystems. Conser ever, does not restrict any activity in the or above its optimum sustainable popu vation and recovery of listed species are area. lation (aSP), while the latter allowed accomplished through the prohibition of On 1 April 1993 (58 FR 17181), the more limited taking without the need certain acts that are known or thought NMFS published a proposal designat to establish the status of the affected to harm the species and by requiring ing Steller sea lion critical habitat which population. Federal agencies to review their pro included terrestrial reproductive and Prior to 1988, many of the Alaskan posed activities throughout the species' resting areas as well as aquatic forag trawl fishery participants were covered range. ing habitats; the final designation of under the MMPA by general permits. Once it is determined that a species critical habitat was published in August However, the Kokechik decision3 should be listed under the ESA, the 1993. Specific areas designated as criti placed most Alaska fisheries in jeopardy agency responsible for management of cal habitat were: since the court refused to allow the the species (e.g., NMFS in the case of 1) All rookeries and major haul outs NMFS to issue general permits for any Steller sea lions) appoints a team of sci (where greater than 200 sea lions had taking if some marine mammals taken entists and managers familiar with the been counted, but where few pups are were not at or above its aSP. Conse biology, history, and management of the present and little breeding takes place), quently, the 1988 amendments to the species. This recovery team is charged including a) a zone 914 m (3,000 feet) MMPA contained provisions for a 5 with drafting a species recovery plan, landward and seaward from each site year interim exemption period to allow which can include recommendations for east of long. 144oW (including those in takes in commercial fisheries while a research into possible causes of the de Alaska, Washington, Oregon, and Cali new management regime was designed. cline and measures to promote recov fornia); and b) a zone 914 m landward This new management regime, con ery. The Steller sea lion recovery team and 36.5 km (20 n.mi.) seaward of each tained in the 1994 amendments to the was formed by the NMFS in March site (36 rookeries and 79 haul outs) west MMPA, requires the NMFS, as part of 1990, 1 month prior to the emergency of long. l44°W where the population an assessment of each marine mammal listing of the species as threatened. The had declined more precipitously and population in U.S. waters, to identify draft Steller sea lion recovery plan was where the former center of abundance strategic stocks, or those which have a completed and made available for pub of the species was located; and level of human-caused mortality that is lic review on 15 March 1991 (56 FR 2) Three aquatic foraging regions likely to cause the stock size to be re 11204), and the final NMFS recovery within the core of the species' range duced or kept below its optimum sus plan was published in December 1992 (Fig. 2). As will be discussed later, spe tainable population. The NMFS must (NMFS,1992). While the team recom cific management measures to separate mended that the NMFS and others (e.g., trawl fisheries from sea lions were taken Alaska Department of Fish and Game) by the NMFS prior to critical habitat 3 Kokechik Fishermen's Association vs. the Sec retary of Commerce. Alaska Native fishing begin a series of long-term monitoring designation. groups and environmental organizations filed and research studies aimed at determin Once a species is listed under the actions after an MMPA general permit to take ing the cause of the sea lion population ESA, specific conservation or recovery Dall's porpoise in fishing operations inside the U.S. EEZ had been issued to the Japan Salmon decline, no specific measures to restrict measures can be taken by the manage Fisheries Cooperative Association. The plaintiffs fisheries were proposed. ment agency at any time. However, the challenged the permit on grounds that the MMPA did not allow issuance of a permit for one spe Section 4 ofthe ESA requires, "to the most powerful tool provided by the ESA cies when other species that were below asp (in maximum extent prudent and determin is probably that contained in Section 7, this case, northern fur seals) would also be taken able," the designation ofcritical habitat which states that Federal agencies must in the same operations. The U.S. District Court for the District of Columbia ruled in favor of the for a threatened or endangered species ensure that their proposed actions are plantiff (June IS, 1987). within 1 year of its listing. Critical habi not likely to jeopardize the continued
16 Marine Fisheries Review Eastern Bering Sea
80905101 Island
Unimak Island
Akutan Island
1620 30' W 1500 W
Figure 2. - Aquatic foraging areas designated as critical habitat for the Steller sea lion in the Gulf of Alaska (Shelikof Strait), eastern Bering Sea (including the area surrounding Bogoslof Island) and Aleutian Islands (Seguam Pass). Other locations mentioned in text are noted. existence of a listed species (a "no jeop formation induced primarily by the pas Strait in 1980. This discovery led to a ardy" decision) or adversely modify its sage of the MFCMA (Megrey and tripling of pollock landings, principally designated critical habitat. A common Wespestad, 1990). This transformation roe-bearing females caught in the win method employed by Federal agencies can best be shown through examination ter and early spring, from the GOA be to ensure a "no jeopardy" decision is to of the trawl fishery for walleye pollock, tween 1980 and 1985 (to about 300,000 consult with the agency responsible for the largest of the groundfish fisheries t; Fig. 4). Concern about declines in the management of the listed species. Sec in the region. Between 1977 and 1992, size of the spawning population in tion 7 consultations involve complete pollock catches accounted for 40-80% Shelikof Strait led the NMFS to drasti descriptions of the proposed activity and of the annual groundfish landings from cally cut the GOA pollock TAC in 1986 any likely impacts on the listed species the GOA and 75-85% ofthose from the to about 80,000 t. Seeking other sources or its designated critical habitat. If a BSAI (NPFMC, 1993a, b). of roe, the joint-venture fishery moved "jeopardy" finding is made, then the One ofthe principal objectives of the to another large spawning assemblage proposed action must be abandoned by MFCMA is to promote full domestic of pollock near Bogoslof Island in the the agency, mitigation measures must use of the offshore fisheries of the eastern Aleutian Basin of the BSAI re be taken to ensure that "jeopardy" will United States. Prior to passage of the gion. In the GOA, both catching and not occur, or a specific exemption can MFCMA, most pollock harvested off processing components of the pollock be provided by the Federal government. Alaska were caught and processed fishery were entirely domestic by 1988, In instances where knowledge of the solely by distant-water fleets of foreign while in the BSAI region a small relationships between the listed species nations, including Japan, the former amount of pollock was allocated to joint and the proposed activity is poor or in U.S.S.R., Republic of Korea, and Po ventures as late as 1990. complete, the ESA requires that conser land (Fig. 3, 4). After passage of the Along with a change in the partici vation and recovery be given the high MFCMA, increasing amounts of pol pants of the pollock fishery came est reasonable priority. lock TAC were allocated to joint ven changes in the temporal and spatial dis tures between domestic catcher vessels tribution of the catch. Between 1977 and Recent History of and foreign processing ships to encour 1992 in both the BSAI region and GOA, Pollock Fisheries off Alaska age development of the domestic fish the pollock fishery worked increasingly During the same period (mid-1970's ing industry. Joint ventures became in fall and winter, took the quota in less to 1990) that the population of Steller most important in the pollock fishery time, and tended to fish more in areas sea lions in Alaska was declining, the first in the GOA after discovery of the which would become designated as groundfish fisheries underwent a trans pollock spawning assemblage in Shelikof critical habitat for Steller sea lions. This
57(2),1995 17 resulted in a temporal compression of the BSAI annual pollock TAC was di fishery began in earnest in 1982 (Fig. the fishery in the fall and winter, and a vided into an "A," or roe season from 6). From 1983 to 1989, catches during spatial compression in sea lion habitats. January to mid-April which initially either the first or last 3 months of the In the BSAI region prior to 1987 received 40% of the TAC and a "B" sea year ranged between 70% and 90% of (when the spawning assemblage near son beginning in June and lasting until the annual catch. In 1990, the GOA Bogoslof Island was first exploited), the the TAC was reached (BSAI FMP pollock TAC was allocated quarterly pollock fishery was conducted prima Amendment 14). This measure, while (GOA FMP Amendment 19) to help rily in July-September when about 50% ensuring sufficient pollock TAC for the prevent its early preemption by large of the landings were taken (Fig. 5). "B" season, also increased the first catcher/processor vessels. These ves From 1987 to 1992, pollock catches quarter's proportion of the annual pol sels, which usually worked in the BSAI during January-March or September lock catch compared with 1977-86. region where the pollock TAC is larger, December increased as the fishery tar A similar change in the temporal dis caught a large percentage of the avail geted the higher-priced roe-bearing fish tribution of effort occurred 5 years ear able pollock TAC in the GOA in a short available in winter. Beginning in 1990, lier in the GOA when the Shelikof roe amount of time, and precluded vessels based in the GOA from pollock fishing
2,000,000 opportunities. The lengths of pollock fishing sea 1,800,000 t5l Domestic , I sons have decreased since the late • Joint-Venture 1,600,000 1980's due primarily to increases in the DForeign fishery's capability to capture fish (Fig. 1,400,000 7). One reason for this change in ca 3 .t= pacity is increases in the sizes of trawls u 1,200,000 ~ used by the fleet. During the early u 1,000,000 1980's (foreign and early joint-venture .Q"" "0 c. fisheries), midwater or pelagic trawls ;;: 800,000 (f) used in the pollock fishery generally had OJ mouth openings in the range of 30-50 600,000 m wide and 15-30 m high (up to 1,500 2 400,000 m trawl mouth areas) and caught 20 80 t in a single tow. As improvements 200,000 in net design, construction, and materi nnn als were made in the mid-late 1980's 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 (Laevastu and Favorite, 1988), larger Year trawls up to 100 m wide, 80 m high (up to 8,000 m2 trawl mouth areas) and 350 Figure 3. - Catches of walleye pollock from the Bering Sea and Aleutian Islands m long were built which could catch as by foreign, joint-venture, and domestic vessels, 1964-92 (data from Wespestad, 1993), much as 400 t in a single haul. The spatial concentration of pollock 350,000 landings from what would be defined as critical habitat for sea lions occurred 300,000 simultaneously with the exploitation of spawning concentrations of pollock 250,000 near Bogoslof Island in 1987 and in 3 .t= .B She1ikof Strait in 1982. Pollock land 200,000 u'" ings (and fishery effort) in BSAI critical u .Q"" habitat increased from about 250,000 t (or "0 c. 150,000 20-30% of the annual landings) in 18 Marine Fisheries Review 70 I_Jan-Mar 0 Apr-Jun I:l Jul-Sep r<:JOct-Dec I 60 400 9.000 350 8.000 7,000 50 ~ 300 6.000 "0 250 5,000 .r:; ~ 200 a 4,000 ~ iii " 40 ~" 150 3,000 '0" ~ 100 2,000 "E 50 1,000 ~ 30 o o a.'" 20 400 1.000 10 350 900 800 II) 300 > 700 ~ 250 a 600 ~ 200 500 a: 400 ~ Year E 150 :J 300 Z 100 200 Figure 5. - Quarterly distribution of walleye pollock catches from the Bering Sea and 50 100 Aleutian Islands by all vessels, 1977-92. o 1987 1988 1989 1990 1991 1992 100 Year 90 I_Jan-Mar DApr-Jun &1Jul-Sep r210ct-Dec I Figure 7. - Length of time (days) that directed fishing for walleye pollock was 80 permitted in the Bering Sea (A) and the Gulf of Alaska (B) for joint venture (JV) 70 and domestic (DOM) vessels. Average catch rate (metric tons (t) ofpollock per day) .r:; >l 60 for each year and area is also plotted. ~ '0 50 "E !!'" a.'" 40 does not appear to have been compro 30 mised (Castellini et aI., 1993; Rea et aI., 20 1993), suggesting that the population decline was not caused by reduced sur 10 vival of nursing pups nor reduced con dition of pregnant or lactating females. More direct evidence for a decline in Year survival rates of weaned pups and ju veniles came from a mark-and-re Figure 6. - Quarterly distribution of walleye pollock catches from the Gulf of Alaska by sighting experiment begun in 1987 and all vessels, 1977-92. 1988, where 424 female pups on Mar mot Island were tagged.4 Female Steller sea lions have a strong fidelity to their 2,9). Pollock landings from GOA criti tion began in the eastern Aleutian Is native rookery when they reach breed cal habitat dropped (as the annual TAC lands and spread to the east and west in ing age (4-5 years), and it was expected declined) to about 50,000 t, and have the 1980's (Braham et aI., 1980; that as many as 100 marked female pups remained at that level through 1992. Merrick et aI., 1987; Loughlin et aI., should have been resighted, beginning However, the percentage of total annual 1992). Results of field and modeling in 1992; however, a maximum of only GOA pollock catches taken from criti studies conducted in the last decade 15 marked females have been resighted. cal habitat did not decline after 1985, but suggest that the most likely proximate Finding the ultimate cause of the has remained between 50% and 90%. cause of the decline is a reduction, per Steller sea lion population decline, or haps between 20% (York, 1994) and the reason for a large reduction injuve Causes of the Steller 60% per year (Pasqual and Adkison, nile survival, has been more difficult. Sea Lion Decline 1994), in the survival of weaned pups The recent (since the 1970's) decline and juveniles. Condition of nursing 4 NMFS Natl. Mar. Mammal Lab., Seattle, Wash. in the Alaskan Steller sea lion popula pups during the first few months of life Unpubl. data. 57(2),1995 19 2.5 A A o Seguam Pass Z' 2.0 ~EBS area o • Haulouts only g Z' 5 o o OJ Rookeries only o 1.5 o o o 4 1.0 0.5 0.0+=...... -,.. 1977 1978 1979 1980 1981 1982 1983 1984 1985 1988 1987 1988 1989 1990 1991 1992 Year 60 100 B 90 B 50 80 40 70 80 30 50 40 20 30 10 20 10 lm,m,m'_I~IE'_'~I_I_I_I_'_'_'~l~ lmlm,ml_'~IE'~I_'_I_'_'_1_'~I~I_ Year Year Figure 8. - Catches of walleye pollock and fishery ef Figure 9. - Catches of walleye pollock and fishery ef fort in Steller sea lion critical habitat in the Bering Sea fort in Steller sea lion critical habitat in the Gulf ofAlaska and Aleutian Islands from 1977 to 1992. A = Pollock from 1977 to 1992. A =Pollock catches from critical catches from critical habitat. B =Percent of total catch habitat. B =Percent of total catch of pollock in the Gulf of pollock in the Bering Sea and Aleutian Islands caught of Alaska caught in critical habitat. in critical habitat. Loughlin5 lists nine potential ultimate factors, entanglement, predation, pollu observed. Similarly, subsistence har causes of the sea lion population de tion, and harassment, could affect ju vests, thought to be on the order of 200 cline, which are (modified slightly): veniles to a greater extent than adults, 700 animals per year (Haynes and entanglement in marine debris, in there is no evidence that any of them, Mishler, 1991; Wolfe and Mishler, creased predation, pollution, harass acting either alone or in concert with 1993) could have affected local groups ment, commercial pup harvests prior to other factors, caused the large reduc but are not likely to have contributed 1972, subsistence harvests, disease, tions in juvenile survival that have significantly to the population decline oceanographic changes, and all of the driven the population decline (NMFS, as a whole. Disease could affect juve effects of fisheries. While four of these 1992). Merrick et al. (1987), Trites and nile survival more than adults. However, Larkin (1992) and Pasqual and Adkison no evidence exists to demonstrate that (1994) examined the possible residual 5 Loughlin, T. R. 1987. Report of the workshop infection rates of known diseases have on the status of northern sea lions in Alaska. U.S. effects of pup harvests on the popula increased or that new diseases among Dep. Commer., NOAA, Natl. Mar. Fish. Serv., tion size and found that they did not juveniles or adults sea lions have de Alaska Fish. Sci. Cent., 7600 Sand Point Way N.E., Seattle, WA 98115-0070. NWAFC Pro produce a decline in size of the adult veloped. Despite this lack of evidence, cessed Rep. 87-04. population of the magnitude or duration disease has not been entirely eliminated 20 Marine Fisheries Review from the list of possible ultimate causes processes which initiate and sustain declines in sea lion numbers observed of the decline, particularly if sea lions them. Similarly, it has not been possible in the 1970's, but they are not thought have been stressed from other causes (T. to sort the effects of removals by fish to have been factors in the steeper de Loughlin6). eries ofcertain fish species on fish com cline observed in the late 1980's Many researchers (e.g., Anderson, munity structure from that induced by (NMFS, 1992). The number of Steller 1991; Hollowed and Wooster, 1992; "natural" change. sea lions killed incidental to fishing Fritz et ai., 1993; Livingston, 1993; operations in the North Pacific has de Fishery and Anderson et ai.?) have documented sub clined significantly in the last 25 years Sea Lion Interactions stantial shifts in the structure and com (Fig. 10) (Loughlin et ai., 1983; Perez position of the North Pacific fish and Interactions between fisheries and and Loughlin, 1991). Sea lion mortal benthic communities over the last 40 Steller sea lions can be divided into two ity attributed to Alaska groundfish fish years, possibly in response to changes basic types (Lowry, 1982): direct or eries averaged over 1,600 animals per in ocean temperature, circulation, or operational, and indirect or biological year from 1968 to 1973, but declined upwelling patterns (Ebbesmeyer et ai., interactions. Direct interactions are to only about 600 per year (except for 1991; Beamish, 1993; Wooster and those in which sea lions are injured or 1982) from 1974 to 1985. In 1982, al Hollowed, In press). Some of the many killed as a result of capture by fishing most 1,800 sea lions were killed by documented shifts in community struc gear (incidental take) or intentional groundfish fisheries, primarily in the ture include increases in the population means (e.g., shooting). Competition for GOA Shelikof Strait pollock fishery. sizes of some semidemersal and dem similar prey resources and disturbance Between 1984 and 1992, the period with ersal species of flatfish and gadids, de by fishing activities are examples of the steepest rate of decline in the sea creases in some pelagic species, such indirect interactions. While data often lion population, mortality associated as herring, Clupea harengus; capelin, are available to describe rates of direct with incidental take in the Alaska Mallotus villosus; and eulachon, Thal interaction (e.g., incidental take), indi groundfish fishery dropped from over eichthys pacificus, decreases in pandalid rect interactions are more difficult to 400 to less than 20 animals per year. shrimps, PandaIus spp., and increases document because they are complex Much of the reduction in incidental take in salmon, Oncorhynchus spp. Since (and as such, hard to measure) and may may have been due to the smaller sea recently weaned sea lions do not appear occur over large areas and at short or lion population size, but some of it is to dive deeper than about 20 m and stay unpredictable time scales. due to changes in fishing techniques, relatively close to shore,4 the availabil such as reducing the amount of time the Direct Interactions ity of prey near the surface or in shal trawl was in the water and not setting with Fisheries low water may be critical to their sur the net in the presence of sea lions vival as they learn to forage for them Direct interactions between Steller (Loughlin and Nelson, 1986). selves. Loughlin and Merrick (1989) sea lions and groundfish fisheries in the The number of sea lions killed by suggest that reductions in juvenile sea GOA and BSAI region contributed to shooting and other intentional means is lion survival rates may be due to de clines in availability (due to lower num 1,800 bers or changes in depth distribution) of their small pelagic prey (e.g., herring, 1,600 capelin, juvenile pollock). Reduced food availability could lead to both star 1,400 vation or increased susceptibility to dis 1,200 ease. Knowledge of how North Pacific '"<:: ~ and Bering Sea biological communities 6 T. Loughlin, NMFS Mar. Mammal Lab., Se attle, Wash. Personal commun., 1994. 7 Anderson, P. J., S. A. Payne, and B. A. Johnson. In prep. Long-term demersal community struc Year ture changes in Pavlof Bay, Alaska. NMFS, Alaska Fisheries Science Center, P.O. Box 1638, Figure 10. - Estimated number of Steller sea lions killed incidental to groundfish fisher Kodiak, AK 99615-1638. ies off Alaska (data from Perez and Loughlin, 1991). 57(2),1995 21 not known. Trites and Larkin (1992) and sea lions for certain species, par suggest that while the school deforms estimated the number shot by fishermen ticularly if the fisheries operate in and has a "hole" in it due to removal of using fishing vessel registrations areas important to sea lions. However, fish and their avoidance of the gear, its records and rates of kill for each vessel attempts to correlate time series of sea structure returns relatively quickly (on type derived from interviews with fish lion abundances on rookeries with the order of tens of minutes) to a pre ery participants. The history of the sub nearby removals of pollock by fisher trawling condition (Nunnallee, 1991). sistence harvest of Steller sea lions by ies have yielded ambiguous results Effects of repeated trawling by many Alaskan native communities was also (Loughlin and Merrick, 1989; Ferrero vessels over several days on fish school recently reviewed (Haynes and Mishler, and Fritz, 1994). structure are not known. However, re 1991; Wolfe and Mishler, 1993). These The selectivities of the fishery and sea movals of large numbers of fish alone analyses and others (Alverson, 1992; lions for various sizes of pollock sug would be expected to decrease either Merrick8) suggest that intentional takes, gests that at some level, there is direct school density or school size for some while they contributed significantly to competition every year there is a fish period of time. Similarly, the effects of the decline in localized areas, were ery (Loughlin and Nelson, 1986). The dispersed prey fields on Steller sea lion not its primary cause throughout the fishery, however, tends to be more size foraging energetics are unknown. How range. selective than sea lions, since it gener ever, data on the effects of reduced prey ally targets and retains pollock greater availability (caused by the 1982-83 EI Indirect Interactions than 30 cm in length (Wespestad and Niiio) on California sea lion foraging with Fisheries Dawson, 1992). Smaller fish are gener energetics suggest that prey dispersion Indirect or biological effects of fish ally caught by the fishery roughly in would likely increase energy expendi ing are difficult to place in perspective proportion to their abundance (Fritz, In ture and search time for food (Trillmich with both the known direct effects of press). On average (based on 1979-92 and Ono, 1991), both disadvantages to fishing and any changes in fish commu data), about 4% of the total population Steller sea lion fitness. nity structure that would have occurred of 2- to 3-year-old pollock (20-35 cm Changes in Fisheries Management naturally due to oceanographic changes. in length) were caught each year by fish Lowry (1982) developed qualitative cri eries in the eastern Bering Sea (EBS), teria for determining the likelihood and and about 2% in the GOA, but very few Listing Regulations: Limiting Potential for Direct Mortality severity ofindirect interactions between 0- to 1-year-old pollock have been fisheries and each marine mammal spe caught. Data available on feeding be To reduce the potential for sea lion cies in the Bering Sea. His criteria used havior suggest that adult Steller sea li mortality from direct human interac information on the species and size ons eat sizes of pollock nearly in pro tions, the NMFS enacted the following composition of each species' diet, its portion to their abundance (Fig. 11, 12), three conservation measures simulta feeding strategy, and importance of the while juvenile sea lions (~4 years old) neously with the listing of Steller sea Bering Sea as a feeding area. Based on may prefer pollock <30 cm in length lions as threatened under the ESA: 1) his assessment, three pinniped species (Calkins and Merrick9). Consequently, shooting at or within 100 yards of a (northern fur seals, Callorhinus ursinus; since both the fishery and sea lions cap Steller sea lion was prohibited, 2) the harbor seals, Phoca vitulina; and Steller ture pollock larger and smaller than 30 number of Steller sea lions that could sea lions), all of which have had major cm, some level of competition for pol be killed incidental to commercial fish declines in abundance over the last 30 lock exists every year (Fig. 11). ing was reduced from 1,350 to 675, and years (Pitcher, 1990; Loughlin et aI., Disturbance from either vessel traf 3) no-entry buffer zones around all 1992; NMFS, 1993), had the greatest fic or fishing activities may also disad Steller sea lion rookeries (where adult potential for adverse indirect interac vantage sea lions, particularly when males actively defend territories and tions with fisheries. they are foraging. Vessel traffic alone most females give birth and mate) west Steller sea lions have a moderately may temporarily cause fish to compress of long. 150 0 W were established. These diverse diet composed primarily of pe into tighter, deeper schools (Freon et aI., measures had only minor impacts on lagic or semidemersal schooling fish, 1992; Nunnallee 10) or split schools into groundfish fisheries in the BSAI and such as walleye pollock, Atka mackerel, smaller concentrations (Laevastu and GOA, but set the stage for other regula Pleurogrammus monopterygius; cape Favorite, 1988). Hydroacoustic obser tions (FMP Amendments) promulgated lin, Pacific herring, and salmon, most vations of the effects of trawling on in response to ESA Section 7 consulta of which are commercially exploited Pacific whiting, Merluccius productus, tions on the GOA pollock fishery. (Calkins and Pitcher, 1982; Lowry, school structure in Puget Sound, Wash. The MMPA prohibited intentional 1982; NMFS, 1992; Calkins and Good lethal takes of Steller sea lions in the win l ; NMML4). This results in some course offishing operations, but did not level of competition between fisheries 9 D. Calkins, Alaska Dep. Fish. Game, and R. prohibit fishermen from harassing those Merrick, Natl. Mar. Fish. Servo Personal commun., 1991. that were interfering with their gear or 8 R. Merrick, Natl. Mar. Fish. Servo Personal 10 E. Nunnallee, Natl., Mar. Fish. Servo Personal catch by shooting at or near them. The commun., 1993. commun., 1994. regulation accompanying the ESA list- 22 Marine Fisheries Review 14 12 1:9 Fishery r.3 Sea lions 10 • NMFS survey cQ) ~ Q) a.. 10 15 20 25 30 35 40 45 50 Pollock length (cm) Figure II. - Length-frequency distributions of walleye pollock caught by the fishery, consumed by Steller sea lions, and the popula tion based on the NMFS bottom trawl survey in spring and summer of 1981 in the Bering Sea. Fishery (April-June) and survey (July September) length-frequencies were from collections in NMFS statistical area 521, located northwest of the Pribiloflslands. Steller sea lions (n=27) were collected pelagically in area 521 in April. Pollock length data (computed from otoliths found in sea lion stomachs) were provided by D. Calkins, Alaska Department of Fish and Game, Anchorage. ing prohibited anyone from shooting at The 1988 amendments to the MMPA facilitate enforcement of the shooting or near Steller sea lions, except: people mandated a maximum mortality of prohibition. However, in discussing the authorized by the endangered species 1,350 Steller sea lions caused by inci reasons for the buffer zones (50 CFR permit provisions (50 CFR part 222, dental takes in fisheries. This figure was Pt. 227 29792), the NMFS also cited subpart C), government officials acting based on the population data collected general concerns about the indirect, to protect the animal's or public's wel in 1985. While incidental take was not nonlethal effects of disturbance and in fare, or Native Americans taking Steller considered to be a major factor in the terference with sea lion behavior at sea lions for subsistence purposes un sea lion decline observed since 1985, these important pupping and breeding der section Wee) of the ESA. Because the permitted level was reduced to re sites. Commercial groundfish fisheries the number of Steller sea lions that had flect the recent (1985-89) decline in the used the marine portion of the no-entry been shot and killed by fishermen prior Alaskan population of Steller sea lions. zones for only a small percentage of to or after this regulation was imple As shown in Figure 10, the reduced their fish catch prior to 1990 (NMFS 11 ). mented is not known, the impact on the level of permitted incidental take (675 However, vessels of all types have used number ofintentional lethal takes of sea sea lions) would not have constrained some no-entry zones for anchorage and lions is also unknown. However, given the groundfish fishery in any of the 5 passage, particularly those around rook the increased awareness of the decline years prior to 1990, nor has it con eries on Akutan Island, Clubbing Rocks, in sea lion numbers as well as the ef strained the fishery since the listing. and Outer Island. Since this regulation fect the decline could have on the fish No-entry buffer zones with a radius was promulgated, specific exceptions ing industry, intentional lethal takes of 3 n.mi. seaward and 800 m landward for transit through the rookery buffer may have declined since the mid-1980's around rookeries were established pri marily to restrict opportunities for in (Alverson, 1992; Trites and Larkin, II Natl. Mar. Fish. Serv., Seattle, Wash. Unpubl. 1992). dividuals to shoot at sea lions and to data. 57(2),1995 23 18 16 I &:I Sea lions • Population model I 14 12 C 10 Ql ~ Ql 0... 8 6 4 2 ~ I ~ ~ ~I o I I l I I • 10 20 30 40 50 60 Pollock length (cm) Figure 12. - Length-frequency distributions of walleye pollock consumed by Steller sea lions and the 1985 Gulf ofAlaska population based on stock-synthesis model output (A. Hollowed, NMFS, Seattle, Wash., 1993, personal commun.). Steller sea lions were col lected in the Kodiak Island Archipelago in summer 1985. Pollock length data (computed from otoliths found in sea lion stomachs) were provided by D. Calkins, Alaska Department of Fish and Game, Anchorage. zones around these three islands have major component of the sea lion diet; was available for harvest in subsequent been granted. 2) sea lions collected near Kodiak Is quarters (temporal allocation), and ex land in the 1980's were lighter, had cluded fishing with trawls within 10 n.mi. ESA Section 7 Consultation smaller girths and thinner blubber lay of all GOA sea lion rookeries. on the 1991 Gulf of Alaska ers than sea lions from the same area The NMFS considered prohibiting Walleye Pollock Fishery: collected in the 1970's; and 3) the pol fishing with any gear within 10 n.mi. Mitigation of Possible lock fishery had become increasingly of rookeries. Both walleye pollock and Indirect Fishery Interactions concentrated in time and in areas Atka mackerel fisheries use trawls ex thought to be important to sea lions. clusively to catch these semidemersal In its ESA Section 7 consultation for While the link between indirect ef schooling species, while other school the 1991 GOA walleye pollock TAC fects of the GOA pollock fishery and ing fishes, such as Pacific cod, Gadus specifications, the NMFS concluded the sea lion decline was circumstantial, macrocephalus, and rockfish, Sebastes that the spatial and temporal compres the NMFS implemented emergency spp., are commercially fished with sion of the pollock fishery that occurred regulations on 13 June 1991 (56 FR trawls, hook and line, and pots. Trawls during the 1980's could have created 28113, June 19, 1991) to reduce the alone were excluded because 1) the risk localized depletions of Steller sea lion potential for competition between them of lethal incidental take of sea lions in prey, which in tum could have contrib to foster sea lion recovery. This was nontrawl fisheries is low, 2) groundfish uted to or exacerbated the decline of the accomplished by dispersing the pollock harvest with trawl gear results in greater sea lion population (5 June 1991). This fishery in time and space and exclud amounts of bycatch of other important conclusion was based on examination ing it from important sea lion habitat. The sea lion prey species, such as juvenile of sea lion food habits and condition specific regulations spatially allocated the pollock, squid and herring, than with data and historical fishing patterns, quarterly GOA pollock TAC between two nontrawl gear, 3) the trawl fishery har some of which is summarized above. areas in the GOA, limited the amount of vests the majority of the catch, and 4) These data revealed that 1) pollock is a unharvested pollock from one quarter that the likelihood of creating localized 24 Marine Fisheries Review depletions of sea lion prey, both com 25 to the GOA FMP, the pollock TAC A recent instance where concerns for mercially exploited and nontarget spe was further dispersed among three in the conservation of Steller sea lions cies, is greater with trawl gear than with stead of two areas as in the emergency were incorporated into the management hooks-and-lines or pots (57 FR 57726). rules, and the rollover limitation (tempo of Alaskan groundfish fisheries oc The NMFS intended to make the ral allocation) was also made permanent. curred in the process of setting ABC's emergency regulations permanent prior The June 1991 emergency regula and TAC's for pollock in the Gulf of to their expiration in December 1991, tions were promulgated to increase the Alaska for the 1993 and 1994 fishing and, at the same time, to place 10 n.mi. likelihood that the Steller sea lion popu seasons. Prior to this time, the size of trawl exclusion zones around sea lion lation would reverse its decline. This the GOA pollock stock was estimated, rookeries in the BSAI. In the interim, conclusion was based on an ESA Sec and the ABC was set each year using the NMFS proposed closing statistical tion 7 consultation that the GOA pol single-species management concepts area 518, the area surrounding Bogoslof lock fishery could have caused local (Pope, 1972; Deriso et aI., 1985; Island (where 30% and 60% of the ized depletions of sea lion prey and thus, Methot, 1990; Clark, 1991). In these BSAI pollock "A" season TAC was contributed to the decline in sea lions. stock assessment models, predation by caught in 1990 and 1991, respectively), This outcome was a direct result of the marine mammals was considered only to directed pollock fishing in 1992. This listing of sea lions as threatened under to the extent that it contributed to some closure was prompted by concerns the ESA. In contrast, the closure of the fraction of the fish stock's natural mor about the decline in size of the Aleu Bogoslof Island district, which was not tality; the indirect effects of prey re tian Basin pollock stock, possibly due considered for sea lion protective pur moval on other fish predators, includ to heavy exploitation from 1986 to 1990 poses, had implications for sea lion re ing marine mammals, was not included. in the international portion of the Bering covery because of a predicted large re Beginning in 1986, ABC's for GOA Sea (the "donut hole"; Wespestad and distribution of pollock fishery effort to pollock were set equal to 10% of the Dawson, 1991). Because the size of the areas soon to be designated as critical exploitable biomass (age 3+ years old), proposed 1992 BSAI "A" season pol habitat. While the increase in size of which is refered to as "the 10% method" lock TAC was similar to that released some trawl exclusion zones during the (Hollowed et aI., 1993). The figure of in 1991 and area 518 was to be closed, pollock "A" season was due to concerns 10% was based on the rate of harvest the fleet would have to fish elsewhere about the effects that redistribution that occurred prior to the years when to achieve its 1992 TAC. The only other would have on the ESA-listed sea lion, large pollock year classes were spawned large assemblage of spawning pollock NMFS implemented these regulations (1975-79). This conservative approach available to the domestic fleet was on as FMP amendments, working through was adopted for the 1986 fishery, and the continental shelf north of Unimak the NPFMC under the auspices of the continued in subsequent years because Island, an area used by sea lions from MFCMA (Gerber, 1993). of large reductions in the size of the the eastern Aleutian Islands for forag Shelikof Strait spawning assemblage Marine Mammal Considerations in ing (letter from S. Pennoyer to N. Fos between 1980 and 1985 and uncertain Setting Quotas for Groundfish ter, November 13, 1991, comments on ties in the assessment of the size of the Fisheries: Incorporation of Marine draft proposed rule for Steller sea lion GOA-wide pollock stock. Using the Mammal ConcerJ;ls and Risk into critical habitat designation). Permanent 10% method to set GOA pollock ABC's Fish Stock Assessments regulations were promulgated imple resulted in lower harvesting rates (catch menting Amendments 20 and 25 to the Prior to 1991, the Plan Teams which divided by biomass) from 1986 to 1992 BSAI and GOA FMP's, respectively, in review stock assessments for each (range 4-8%, median=6%) than if, for January 1992 (57 FR 2683, January 23, groundfish species or species complex instance, the BSAI harvesting rate had 1992). These regulations increased the were composed solely of fishery biolo been used (range 7-20%, median=13%) radius of the no-trawl exclusion zones gists and Federal and state resource (Hollowed et aI., 1993; Wespestad, from 10 to 20 n.mi. around five rooker managers. With the listing of Steller sea 1993). ies in the eastern Aleutian Islands until lions under the ESA in 1990 and the In 1992 (for the 1993 season), the 15 April each year to further separate accompanying increase in awareness of SSC questioned the biological rationale trawl fisheries, particularly the pollock the potential for marine mammal con for the GOA pollock fishing mortality trawl fisheries concentrated on the east cerns to affect groundfish fisheries, rate because it was inconsistent with the ern Bering Sea shelf, from sea lions. marine mammal biologists were ap current understanding of pollock popu These rookeries were located on Sea pointed to the BSAI Plan Team in 1991, lation dynamics as well as rates used to Lion Rocks, and Akun, Akutan, Seguam, and to the GOA Plan Team in 1992. In set BSAI pollock ABC's. While the SSC and Agligadak Islands. 12 In Amendment this manner, recent information on was aware of Steller sea lion conserva population status, food habits, and ma tion concerns and the potential for a link 12 A 20 n.mi. BSAI "A" season trawl exclusion rine mammal/fishery interactions can be with commercial fisheries removals, the zone was placed around the rookery on Ugamak discussed directly by the Plan Teams dur pollock exploitation issue reflected the Island in 1993 to better encompass the range of winter habitats and juvenile foraging areas uti ing their deliberations on groundfish stock MFCMA mandate to manage fish lized by sea lions in the eastern Aleutian Islands. assessments and ABC determinations. stocks using the best available scientific 57(2),1995 25 information. In this case, setting the mals. The SSC acknowledged several assessments and ABC determinations, GOA pollock ABC at 10% or any other concerns noted by the GOA Plan Team although other conservative approaches percentage of the exploitable biomass in its review of the pollock stock assess are currently being considered. The strat was not supported by data on the biol ment, including the reduced size of the egy could be modified as the status of the ogy of pollock, but on the history of the pollock stock and the low levels of re pollock stock changes or as more infor pollock fishery. cent recruitment. In addition, the SSC mation on the relationship between Steller Consequently, Hollowed et aI. (1993) also recognized that the population size sea lions and pollock becomes available. developed several alternative ways of of Steller sea lions in the GOA contin Acknowledgments examining the effects of various fish ued to decline. Despite the lack of hard ing mortality rates (F), including one evidence linking pollock fishery remov The authors wish to thank H. Braham, which balanced yield with the risk of als with the sea lion decline, the SSC A. Hollowed, T. Loughlin, R. Marasco, reducing spawner biomass below a expressed its desire for a cautious ap S. Mello, R. Merrick, R. Methot, and threshold level. The models they em proach in setting the ABC for pollock V. Wespestad for their comments on the ployed estimated process error (from to reduce the likelihood that pollock manuscript. Editorial assistance was highly variable recruitment and an ap removals or fishery activity would ex provided by G. Duker and J. Lee. parent shift in the probability of a strong acerbate the sea lion decline. Literature Cited year class recruiting to the population) During the 1993 GOA Plan Team as well as measurement error. Their meetings (which review the assessments Alverson, D. L. 1992. A review of commercial fisheries and the Steller sea lion (Eumetopias approach resulted in a higher value of for the 1994 fishery), the Hollowed/ jubatus): the conflict arena. Rev. Aquat. Sci. F than when ABC was set to 10% of Megrey method for examining fishing 6(3-4):203-256. Anderson, P. J. 1991. Age, growth, and mortal the exploitable biomass, but it repre mortality rates by balancing fishery ity of the northern shrimp Pandalus borealis sented a departure from the traditional yield with risk of the stock falling be Krtiyer in Pavlof Bay, Alaska. Fish. Bull. management strategy by introducing the Iowa spawning biomass threshold was 89:541-553. Beamish, R. J. 1993. Climate and exceptional fish concept offoregoing catch to reduce the altered somewhat by only considering production offthe west coast ofNorth America. risk of further reductions to spawning the risk component in setting F. The Can. J. Fish.Aquat. Sci. 50:2270-2291. stock biomass. In addition, prey avail result was a more conservative ABC Braham, H. W., R. D. Everitt, and D. J. Rugh. 1980. Northern sea lion population decline in ability for other predators, such as ma compared with that resulting from bal the eastern Aleutian Islands. J. Wild!. Man rine mammals and birds, was addressed ancing yield and risk, and a clear rec age. 44(1):25-33. Calkins, D. G., and K. W. Pitcher. 1982. Popula in the model since it incorporated esti ognition that while short-term fishery tion assessment, ecology, and trophic relation mates of the probability of the spawn catches would be foregone, the risk of ships of Steller sea lions in the Gulf of Alaska. ing pollock population biomass declin falling to historic lows in spawner bio Alaska Dep. Fish Game, 333 Raspberry Road, An chorage. Final Rep. Contr. 03-5..Q22-69, 129 p. ing below a predetermined level. The mass would be decreased. The level of Castellini, M. A., R. W. Davis, T. R. Loughlin, risk parameter was introduced despite risk that was acceptable to the GOA and T. M. Williams. 1993. Blood chemistries the highly variable relationship between Plan Team, 5% chance ofthe stock faIl and body condition of Steller sea lion pups at Marmot Island, AK. Mar. Mammal Sci. the numbers of spawners and recruits ing below the spawning biomass thresh 9:202-208. into the GOA pollock population, and old, was based largely on an a-level Clark, W. G. 1991. Groundfish exploitation rates the absence of data suggesting that a commonly used in statistical tests. The based on life history parameters. Can. J. Fish. Aquat. Sci. 48:734-750. particular spawner biomass threshold Plan Teams' recommendation was Deriso, R. B., T. J Quinn II, and P. R. Neal. 1985. was biologically meaningful. Therefore, based not only on the declining trend Catch-age analysis using auxiliary informa tion. Can. J. Fish. Aquat. Sci. 42:815-824. this approach reflected the caution of in the pollock resource, but also on Ebbesmeyer, C. C., D. R. Cayan, D. R. McLain, the GOA Plan Team in preserving pol avoiding potential harm to Steller sea F. H. Nichols, D. H. Peterson, and K. T. lock biomass in the face of a declining lions. This marked the first instance in Redmond. 1991. 1976 step in the Pacific cli mate: forty environmental changes between stock size and acknowledged that the the management of Alaska groundfish 1968-1975 and 1977-1984. In J. L. Betan pollock resource is important to other fisheries where an exploitation strategy court and V. L. Tharp (Editors), Proceedings marine organisms including Steller sea of the Seventh Annual Pacific Climate for an important commercial fishery (PACLIM) Workshop, April 1990, p. 115-126. lions and marine birds. resource directly incorporated a safe Calif. Dep. Water Resour., Interagency Eco!. While the SSC considered recom guard for a marine mammal species Stud. Prog. Tech. Rep. 26. Ferrero, R. c., and L. W. Fritz. 1994. Compari mending using the yield/spawner bio from its inception in the Plan Team sons of walleye pollock, Theragra chalco mass model in assessing the size of the through subsequent approval by the gramma, harvest to Steller sea lion Eume 1993 pollock stock, it chose to recom SSC, AP, and NPFMC. topias jubatus, abundance in the Bering Sea and Gulf of Alaska. U.S. Dep. Commer., mend a lower ABC using the 10% Incorporation of risk estimation into NOAA Tech. Memo. NMFS-AFSC-43, 25 p. method. The SSC reasoned that a large fish stock assessments and fishery man Freon, P., F. Gerlotto, and M. Soria. 1992. increase in pollock removals, which agement is not unique to the GOA pol Changes in school structure according to ex ternal stimuli: description and influence on would have occurred had the yield/risk lock, but it is being used in a number of acoustic assessment. Fish. Res. 15:45-66. approach to setting F been adopted, may fisheries in a wide variety of ways Fritz, L. W. In press. Juvenile walleye pollock, Theragra chalcogramma, bycatch in commer not be adequately conservative for the (Smith et al., 1993). The risk approach cial groundfish fisheries in Alaskan waters. pollock resource or for marine mam is expected to be used in future stock In R. Brodeur, A. Hollowed, P. Livingston, and 26 Marine Fisheries Review T. Loughlin (Editors), Workshop on the im Lowry, L. E 1982. Documentation and assess Pope, J. G. 1972. An investigation of the accu portance of prerecruit walleye pollock to the ment of marine mammal-fishery interactions racy of virtual population analysis using co Bering Sea and North Pacific ecosystems, 28 in the Bering Sea. In K. Sobol (Editor), Trans. hort analysis. Res. Bull. Int. Comm. North 30 October 1993, Seattle, Wash. V.S. Dep. 47th N. Am. Wildl. and Nat. Resour. Conf., west Atl. Fish. 9:65-74. Commer., NOAA Tech. Rep. NMFS. 26-31 March 1982, Portland, Oreg., p. 300 Rea, L. D., M. A. Castellini, and R. L. Merrick. _-:-::-:::-::--,; , V. G. Wespestad, and J. S. Collie. 311. Wildl. Manage. Inst., Wash., D.C. 1993. Body condition and metabolic chemis 1993. Distribution and abundance trends of Megrey, B. A., and V. G. Wespestad. 1990. Alas try of Steller sea lion pups in the Aleutian Is forage fishes in the Bering Sea and Gulf of kan groundfish resources: 10 years of man lands and Gulf of Alaska. Abstr. Tenth Alaska. In Is it food?: addressing marine agement under the Magnuson Fishery Con Bienniel Conf. BioI. Mar. Mamm., Galveston mammal and sea bird declines. Workshop servation and Management Act. N. Am. J. TX, ll-15 Nov. 1993. summary, p. 30-43. Alaska Sea Grant Rep. Fish. Manage. 10: 125-143. Smith, S. J., J. J. Hunt, and D. Rivard. 1993. Risk 93-01. Vniv. Alaska, Fairbanks. Merrick, R. L., T. R. Loughlin, and D. G. Calkins. evaluation and biological reference points for Gerber, L. R. 1993. Endangered Species Act de 1987. Decline in abundance of the northern fisheries management. Can. Spec. Publ. Fish. cision-making in the face of scientific uncer sea lion, Eumetopiasjubatus, in Alaska, 1956 Aquat. Sci. 120. tainty: a case study of the Steller sea lion. 86. Fish. Bull. 85:351-365. Trillmich, E, and K. Ono 1991. Pinnipeds and MMA Thesis, Vniv. Wash., Seattle. Methot, R. D. 1990. Synthesis model: an adapt El Niiio: responses to environmental stress. Haynes, T. L., and C. Mishler. 1991. The subsis able framework for analysis of diverse stock Ecol. Stud. 88, Springer-Verlag, NY. tence harvest and use of Steller sea lions in assessment data. Int. N. Pac. Fish. Comm., Trites, A. w., and P. A. Larkin. 1992. The status Alaska. Alaska Dep. Fish Game, Div. Subsis Bull. 50:259-277. of Steller sea lion populations and the devel tence, Tech. Pap. 198,47 p. NMFS. 1992. Recovery plan for the Steller sea opment of fisheries in the Gulf of Alaska and Hollowed, A. B., B. A. Megrey, and E. Brown. lion (Eumetopias jubatus). Rep. prep. by Aleutian Islands: Report to the Pacific States 1993. Walleye pollock. In Stock assessment Steller sea lion Recovery Team for Nat. Mar. Marine Fisheries Commission. Vniv. Brit. and fishery evaluation report for the ground Fish. Ser., NOAA, Silver Spring, Md. Col., Fish. Cent. Rep., 133 p. fish resources of the Gulf of Alaska as pro __--,-_. 1993. Conservation plan for the north Wespestad, V. G. 1993. Walleye pollock. In Stock jected for 1994, p. 1-1 to I-54. N. Pac. Fish. ern fur seal (Callorhinus ursinus). V.S. Dep. assessment and fishery evaluation report for Manage. Counc., P.O. Box 103136, Anchor Commer., NOAA, Natl. Mar. Fish. Serv., the groundfish resources of the Bering Seal age, AK 99510. Conserv. Plan, 78 p. Aleutian Islands regions as projected for 1994, _---;:----:_ and W. S. Wooster. 1992. Variability NPFMC. 1993a. Stock assessment and fishery p. 1-1 to 1-26. N. Pac. Fish. Manage. Comm., of winter ocean conditions and strong year evaluation report for the groundfish resources P.O. Box 103136, Anchorage, AK 99510. classes of northeast Pacific groundfish. ICES of the Bering SealAleutian Islands regions as _-=--=-_and P. Dawson. 1991. Walleye pollock. Mar. Sci. Symp. 195:433-444. projected for 1994. N. Pac. Fish. Manage. In Stock assessment and fishery evaluation Laevastu, T., and E Favorite. 1988. Fishing and Counc., P.O. Box 103136, Anchorage, AK report for the groundfish resources of the stock fluctuations. Fishing News Books Ltd., 99510. Bering SealAleutian Islands regions as pro Farnham, Surrey, Engl., 239 p. __...,..-_. 1993b. Stock assessment and fishery jected for 1992, p. 1-1 to 1-27. N. Pac. Fish. Livingston, P. 1993. Importance of predation by evaluation report for the groundfish resources Manage. Comm., P.O. Box 103136, Anchor groundfish, marine mammals and birds on of the Gulf of Alaska as projected for 1994. age, AK 99510. walleye pollock Theragra chalcogramma and N. Pac. Fish. Manage. Counc., P.O. Box _~;o--and . 1992. Walleye pollock. Pacific herring Clupea pallasi in the eastern 103136, Anchorage, AK 99510. In Stock assessment and fishery evaluation Bering Sea. Mar. Ecol. Prog. Ser. 102:205-215. Nunnallee, E. P. 1991. An investigation of the report for the groundfish resources of the Loughlin, T. R., L. Consiglieri, R. L. DeLong, avoidance reactions of Pacific whiting (Mer Bering SealAleutian Islands regions as pro and A. T. Actor. 1983. Incidental catch of luccius productus) to demersal and midwater jected for 1993, p. I-I to 1-32. N. Pac. Fish. marine mammals by foreign fishing vessels, trawl gear. Int. Counc. Explor. Sea, Pap.IB:5, Manage. Counc., P.O. Box 103136, Anchor 1978-81. Mar. Fish. Rev. 45(7-8-9):44-49. Sess. V., Fish Capture Committ., 17 p. age, AK 99510. _---;:-__ and R. L. Merrick. 1989. Comparison Pasqual, M., and M. Adkison. 1994. The decline Wolfe, R. J., and C. Mishler. 1993. The subsis of commercial harvest of walleye pollock and of the Steller sea lion in the northeast Pacific: tence harvest of harbor seal and sea lion by northern sea lion abundance in the Bering Sea demography, harvest or environment? Ecol. Alaska natives in 1992. Alaska Dep. Fish and Gulf ofAlaska. In Proceedings of the In App. 4:393-403. Game, Juneau. Tech. Pap. 229, Pt. I, Final ternational Symposium on the Biology and Perez, M. A., and T. R. Loughlin. 1991. Inciden Rep. Year I, Subsistence study and monitor Management ofWalleye Pollock, p. 679-700. tal catch of marine mammals by foreign and system, prep. for NMFS. Vniv. Alaska Sea Grant Rep. 89-01. joint venture trawl vessels in the V.S. EEZ of Wooster, W. S., and A. B. Hollowed. In press. ___-:-: and R. Nelson, Jr. 1986. Incidental the North Pacific, 1973-88. V.S. Dep. Decadal scale variations in the eastern sub mortality of northern sea lions in Shelikof Commer., NOAA Tech. Rep. NMFS 104,57 p. arctic Pacific: A. Winter ocean conditions. Strait, Alaska. Mar. Mammal Sci. 2: 14-33. Pitcher, K. W. 1990. Major decline in number of Can. Spec. Publ. Fish. Aquat. Sci. _..,...,.-.,.."...... , , A. S. Perlov, and V. A. Vladimirov. harbor seals, Phoca vitulina richardsi, on York, A. E. 1994. The population dynamics of 1992. Range-wide survey and estimation of Tugidak Island, Gulf of Alaska.. Mar. Mam northern sea lions, 1975-1985. Mar. Mammal total number of Steller sea lions in 1989. Mar. mal Sci. 6: 121-134. Sci. 10:38-51. Mammal Sci. 8(3):220-239. 57(2),1995 27