Status Review of Pacific Hake,
Richard G. Gustafson, William H. Lenarz,
National Marine Fisheries Service
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Marine Fisheries Service
NOAA-NWFSC Tech Memo-44: Status Review of Pacific
Hake, Pacific Cod, and Walleye Pollock
from Puget Sound, Washington
NOAA Technical Memorandum NMFS Series
The Northwest Fisheries Science Center of the National Marine Fisheries Service, NOAA, uses the NOAA Technical Memorandum NMFS series to issue informal scientific and technical publications when complete formal review and editorial processing are not appropriate or feasible due to time constraints. Documents published in this series may be referenced in the scientific and technical literature.
The NMFS-NWFSC Technical Memorandum series of the Northwest Fisheries Science Center continues the NMFS-F/NWC series established in 1970 by the Northwest & Alaska Fisheries Science Center, which has since been split into the Northwest Fisheries Science Center and the Alaska Fisheries Science Center. The NMFS-AFSC Technical Memorandum series is now being used by the Alaska Fisheries Science Center.
Reference throughout this document to trade names does not imply endorsement
by the National Marine Fisheries Service, NOAA.
This document should be cited as follows:
Gustafson R.G., W.H. Lenarz, B.B. McCain, C.C.
Schmitt, W.S. Grant, T.L. Builder, and R.D. Methot.
2000. Status review of Pacific Hake, Pacific Cod, and
Walleye Pollock from Puget Sound, Washington. U.S.
Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-
44, 275 p.
Most NOAA Technical Memorandums NMFS-NWFSC are
available on-line at the Northwest Fisheries Science Center
web site (http://www.nwfsc.noaa.gov)
Copies are also available from:
National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road
Springfield, VA 22161
The Endangered Species Act (ESA) allows the listing of "distinct population segments"(DPSs) of vertebrate species or subspecies as threatened or endangered, if severe declines in abundance are indicated or substantial risks are facing the species. Thus, two key questions must be addressed in determining whether a listing under the ESA is warranted: 1) Is the entity in question a "species" as defined by the ESA? and 2) If so, is the "species" in danger of extinction (endangered) or likely to become so (threatened)? Guidance on what constitutes a "distinct population segment" is provided by the joint U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS) interagency policy on vertebrate populations (USFWS-NMFS 1996). Once a DPS is identified, NMFS considers a variety of factors in determining whether a listing is warranted.
In response to a petition to list 18 species of marine fish in Puget Sound under the ESA (Wright 1999), NMFS initiated status reviews of seven of these species: Pacific hake, Merluccius productus (Ayres, 1855); Pacific cod, Gadus macrocephalus Tilesius, 1810; walleye pollock, Theragra chalcogramma (Pallas, 1815); Pacific herring, Clupea pallasi Valenciennes, 1847; brown rockfish, Sebastes auriculatus Girard, 1854; copper rockfish, S. caurinus Richardson, 1845; and quillback rockfish, S. maliger Jordan and Gilbert, 1880. NMFS formed a Biological Review Team (BRT), composed of scientists with expertise in one or more of these species, to conduct these status reviews. This report summarizes the biological and environmental information gathered in that process and the scientific conclusions reached by the BRT for Pacific hake, Pacific cod, and walleye pollock. Since these latter three species are members of the Order Gadiformes (Cohen et al. 1990, Robins et al. 1991, Eschmeyer 1998) they are jointly referred to as gadiforms throughout this document. This review is part of a larger effort by the National Marine Fisheries Service to complete status reviews for all seven of the petitioned species of marine fish in Puget Sound.
The BRT examined environmental, geologic, biogeographic, life history, and genetic information in the process of identifying DPSs that satisfy ESA and joint interagency policy definitions (USFWS-NMFS 1996) of "discreteness" and "significance." In particular, geographically-discrete and temporally-persistent spawning aggregations, tagging data, biogeography, ecological and habitat factors, and variation in seasonal migration patterns, parasite incidence, and genetic population structure were found to be most informative for this process. Data relating to group or stock demographics (year-class strength, growth rate, body size at maturity, age at maturity, length frequency, fecundity, etc.) and morphometrics and meristics were less informative for DPS delineation, since the extent to which these characteristics are influenced by environmental or genetic differences is relatively unknown. Based on this examination, the BRT identified a DPS for Pacific hake and a DPS for walleye pollock in this region that can be considered species under the ESA. The BRT also concluded that there is good reason to believe that Pacific cod from Puget Sound are part of a DPS that extends beyond the boundaries of the Puget Sound ecosystem, to at least as far north as Dixon Entrance.
The ESA (section 3) defines the term "endangered species" as "any species which is in danger of extinction throughout all or a significant portion of its range." The term "threatened species" is defined as "any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range." According to the ESA, the determination of whether a species is threatened or endangered should be made on the basis of the best scientific information available regarding its current status, after taking into consideration conservation measures that are proposed or are in place. In this review, the BRT did not evaluate likely or possible effects of conservation measures, and therefore did not make recommendations as to whether identified DPSs should be listed as threatened or endangered species; rather, the BRT drew scientific conclusions about the risk of extinction faced by identified DPSs, under the assumption that present conditions will continue.
The majority of the BRT concluded that the Pacific hake DPS, the walleye pollock DPS, and all three potential DPS scenarios for Pacific cod in the Eastern Pacific are not in danger of extinction. Although the BRT concluded that none of the population segments of the three gadiform species examined is in danger of extinction, in each case, the BRT acknowledged that their level of concern would have been elevated if the geographic size of the DPSs or population segments examined had been smaller.
The BRT concluded that inshore resident Pacific hake from Puget Sound and the Strait of Georgia constitute the Georgia Basin Pacific hake DPS(Fig. 1). The Georgia Basin is comprised of the marine waters of the Strait of Georgia, Puget Sound, and eastern Strait of Juan de Fuca. The BRT identified a variety of evidence to support their conclusion that Georgia Basin Pacific hake constitute a separate DPS relative to offshore Pacific hake: 1) Differences in annual migration behavior, 2) significant allozyme frequency differences between Puget Sound and offshore Pacific hake, 3) absence of the protozoan parasite Kudoa paniformis in inshore populations compared to its common occurrence in offshore Pacific hake, 4) differences in otolith morphology between Strait of Georgia and offshore Pacific hake, 5) distinctiveness of the habitats of inshore Pacific hake (they spawn in deep, inshore basins that receive large freshwater inputs and are the only populations of Pacific hake that inhabit fjord-like environments), 6) wide geographic separation of inshore and offshore spawning locales, and 7) demographic data showing that inshore Pacific hake are generally smaller for a given age, mature at a smaller size, and reach a smaller maximum length than offshore fish. The BRT expressed several concerns about the available data; for example: 1) it is not clear whether demographic differences between Georgia Basin and offshore Pacific hake are driven by environmental or genetic differences, 2) some of the allozyme loci that show differences between Puget Sound and offshore Pacific hake have been shown to be under selection in other animals, and 3) there is no obvious physical barrier preventing mixing of offshore and Georgia Basin Pacific hake, especially during the June-August period when offshore Pacific hake may occur near the mouth of the Strait of Juan de Fuca.
The BRT concluded that the Georgia Basin Pacific hake DPS was not presently in danger of extinction, but could with nearly equal likelihood fall into either of two categories:
1) not in danger of extinction, nor likely to become so in the foreseeable future, or 2) not presently in danger of extinction, but likely to become so in the foreseeable future. As a whole, the BRT gave slightly higher support to the first category. The biomass of Pacific hake in Port Susan during the spawning period has declined by 85% over the past 15 years, yet numbers have fluctuated around 30 million fish until dropping to less than 11 million in 2000. Over the same period, size composition and size-at-maturity for females have also decreased substantially. In contrast, such significant declines in biomass, fish size, or maturity, are not evident for Pacific hake populations in the Canadian portion of the Strait of Georgia and these populations are much larger than the Port Susan population.
In addition to the concerns about the status of Puget Sound Pacific hake, the BRT identified several areas of uncertainty regarding the relationships among stocks and effects of potential risk factors. The extent of any mixing of spawning products or spawners among stocks within the Georgia Basin is unknown. Risk factors are also poorly known and for the most part, the BRT could only speculate on potential factors and their effects. For example, two hypothetical models of pinniped predation on Pacific hake in Port Susan were considered, but the results were inconclusive.
Over the next year, much new information is expected to become available that will likely resolve many of the uncertainties about the status and relationship of stocks of Pacific hake within the Georgia Basin DPS. When it is available, the BRT urges that this new information be considered and extinction risk be reevaluated.
The majority opinion of the BRT was that there is good reason to believe that Pacific cod from Puget Sound are part of a DPS that is larger than Puget Sound and that this DPS extends northward to at least Dixon Entrance (Fig. 2). However, the BRT concluded that there is insufficient information available at present to identify the exact northern boundary of the DPS that incorporates Puget Sound Pacific cod. A high level of uncertainty concerning the northern boundary of the DPS was expressed during the decision-making process, and the BRT agreed that there is insufficient information available at present to identify DPSs of Pacific cod with a high degree of certainty. The BRT struggled with this decision and noted that the lack of suitable data to answer the DPS question for Pacific cod was a cause for concern.
The conclusion that the Pacific cod DPS is larger than Puget Sound was supported by:
1) genetic data that show a lack of significant heterogeneity among Pacific cod sampled largely during summer and fall at various locations in the northeastern Pacific Ocean (although it is possible that if collections had been of spawning fish the data might have shown greater population structure), 2) results of adult tagging studies in the Strait of Georgia and Puget Sound showing movement amongst inshore locations and some limited movement between inshore and coastal areas (although rare tagging studies on spawning fish do show some level of spawning site fidelity), and 3) the ecological similarity of fjord-type marine habitat in Puget Sound to habitat along the coasts of British Columbia and southern Alaska.
The BRT considered several scenarios as to where the northern boundary of the DPS may occur, including: 1) the northern extent of the Georgia Basin (encompassing the Strait of Georgia, Puget Sound, and the eastern Strait of Juan de Fuca), 2) the north end of Vancouver Island (encompassing the Georgia Basin and Amphitrite Bank spawning aggregations), 3) Dixon Entrance, and 4) Southeast Alaska. Although the BRT was unable to determine the exact northern boundary of the Pacific cod DPS, a majority of the BRT felt that the northern boundary of the Pacific cod DPS extends at least as far north as Dixon Entrance.
Although the BRT could not with any certainty identify multiple populations or DPSs of Pacific cod within the region south of Dixon Entrance/Southeast Alaska, they acknowledged the possibility that significant stock structuring does exist within this region and that a finer DPS structure might be revealed by further information on the behavior, ecology, and genetic population structure of Pacific cod. The BRT recognized that the DPS, that includes Puget Sound Pacific cod, may represent fish that are uniquely adapted to survive at the southern end of the species' range.
As with the northern boundary considerations for the Pacific cod DPS, the BRT struggled with the assessment of extinction risks. Of the four scenarios considered for the northern boundary of the DPS for Pacific cod (see summary above), the BRT did not distinguish between DPS scenarios 1 and 2 for its extinction risk assessment. The BRT considered risks for three DPS scenarios: 1) Georgia Basin, 2) Puget Sound to Dixon Entrance, and 3) Puget Sound through Southeast Alaska.
In general, as the size of the DPS grew to encompass more spawning locations and greater numbers of Pacific cod, the BRT considered the risks of extinction to diminish. The majority of the BRT concluded that Pacific cod encompassed by DPS scenarios 2 (Puget Sound to Dixon Entrance) and 3 (Puget Sound through Southeast Alaska) are not in danger of extinction, nor are they likely to become so in the foreseeable future. A minority of the BRT felt that Pacific cod within either DPS scenario 2 or 3, although not presently in danger of extinction, are likely to become so in the foreseeable future. In fact, most BRT members could not rule out the possibility that Pacific cod in DPS scenario 2 (Puget Sound to Dixon Entrance) are likely to become endangered in the foreseeable future.
The BRT was divided on the extinction risk status of Pacific cod encompassed by scenario 1 (Georgia Basin). Although the BRT agreed that Pacific cod in the Georgia Basin scenario are not presently in danger of extinction, the BRT was nearly equally divided on the question of whether Pacific cod in this population segment are likely to become endangered in the foreseeable future if present trends continue. As a whole, the BRT gave slightly higher support to placing Pacific cod in this population segment in the category of not in danger of extinction, nor likely to become so in the foreseeable future.
The BRT identified several concerns: 1) the apparent loss of the major, known spawning locations in Puget Sound, 2) general synchronicity in declining trends in Pacific cod abundance from Puget Sound to Southeast Alaska, and 3) relatively little quantitative information or understanding about the effects of potential risk factors. Overall, it is not certain which risk factors, either singly or in combination, may be significantly contributing to the current low stock sizes of Pacific cod.
The BRT concluded that aggregations of spawning walleye pollock in the eastern North Pacific Ocean, south of a provisional northern boundary of 140oW, are part of a single DPS, which is the Lower boreal Eastern Pacific walleye pollock DPS. The DPS name is derived from the zoogeographic literature, which describes the general area occupied by this unit as containing a "well-defined lower boreal fauna" (Briggs 1974, p. 278). The provisional northern boundary of the Lower boreal Eastern Pacific DPS coincides with the northern and western stock boundary for Southeast Alaska walleye pollock at 140oW (Fig. 3).
The BRT's conclusion that a walleye pollock DPS extends from Puget Sound northward to encompass all of Southeast Alaska, with a provisional northern boundary at 140oW, was supported by the following considerations: 1) the walleye pollock reproductive traits of pelagic spawning and pelagic distribution of eggs and larvae, 2) the ecological similarity of fjord-type marine habitat in Puget Sound to habitat along the coasts of British Columbia and Southeast Alaska, 3) the more or less continuous distribution of spawning sites for walleye pollock within the geographic confines of the DPS, 4) that regulatory agencies in the area consider walleye pollock in northern British Columbia and Southeast Alaska to consist of a single stock, 5) recognition of a significant zoogeographic faunal break in Southeast Alaska, 6) the consideration that walleye pollock from Puget Sound through Southeast Alaska are spawning in fjords, whereas further north walleye pollock are spawning in more open water, and 7) the unlikely potential for walleye pollock from Southeast Alaska to mix with walleye pollock from the central and western Gulf of Alaska. The BRT did not preclude the possibility that further information on the behavior, ecology, and genetic population structure might provide a basis for delineating smaller DPSs of walleye pollock within the Lower boreal Eastern Pacific DPS.
Although the BRT could not with any certainty identify multiple populations or DPSs of walleye pollock within the Lower boreal Eastern Pacific DPS, they acknowledged the possibility that more than one DPS for walleye pollock may exist in the range from Puget Sound to Southeast Alaska. However, the BRT was unable to find compelling evidence that this finer DPS structure exists. As an example of the uncertainty inherent in the walleye pollock DPS decision, it should be noted that none of the BRT members ruled out the possibility that there could be a DPS for walleye pollock at the level of the Georgia Basin.
The BRT concluded that walleye pollock in the Lower boreal Eastern Pacific DPS are not in danger of extinction, nor are they likely to become endangered in the foreseeable future if present trends continue. However, most BRT members could not entirely rule out the possibility that walleye pollock in this DPS, although not presently in danger of extinction, are likely to become so in the foreseeable future.
Information on the status of walleye pollock stocks in the DPS is very limited and usually based on catches or catch rates in recreational or commercial fisheries. The abundance of walleye pollock in Puget Sound is at low levels, especially in southern areas, but stocks outside Puget Sound do not appear to be at or declining to such low levels. As with Pacific hake and Pacific cod, little quantitative information is available about potential risk factors or their effects on the status of walleye pollock in the DPS. The lack of suitable data to assess extinction risk is a cause for concern.
It is important
to note that the BRT's considerations of the status and trends of Pacific
hake, Pacific cod, and walleye pollock in the Puget Sound area did not,
and should not, occur in a vacuum. In addition to these three species,
several other fish species from this area have either been listed under
the ESA, or have been petitioned for listing. These include 23 ESUs of
anadromous salmonids in the Pacific Northwest, Pacific herring, and various
species of rockfish-in or close to the Puget Sound area. A significance
emerges from consideration of these species collectively that is not apparent
when any one is considered alone. Joint consideration of these species
together suggests ecosystem-level implications that are difficult or impossible
to evaluate under terms of the ESA. It is possible, hypothetically, that
the reduced or declining trends of each of the individual species in this
group could be considered as insufficient for affording any of the species
legal protection under the ESA. But taking no action, under such circumstances,
might be a major mistake if this collective information is an indication
that the Puget Sound area, as an ecosystem, is experiencing major change.
Such changes could be of more far-ranging concern than could ever be recognized
if any one species were considered individually. Environmental variation
and general ecosystem dynamics, could easily lead to at least some of the
declines in abundance observed for any one of these species. The commonalities
and synchronous nature of the information is compelling, and scientifically,
this raises the need to determine the degree to which these common changes
are anthropogenic, both for individual species and within the Puget Sound
ecosystem as a whole. The complexity of factors responsible for population
fluctuations emphasizes the need for better understanding of the unique
features of Puget Sound compared to surrounding and similar environments,
many of which are interconnected with the Sound via such factors as the
climate, currents, migrations, and dispersal of various species. It is
important to understand the natural variation within such systems over
various time scales from decades to thousands of years. The potential for
stratigraphic sediment analysis is noted in this regard. So are studies
of the dynamics of species compared across the observed diversity of life-history
strategies. Measures of the ebb and flow, or the extinction, recolonization,
and persistence of the populations of the various species in the Puget
Sound ecosystem are important as a basis for judging how problematic the
picture before us is, to what degree the changes are of anthropogenic origins,
and how significant these changes are as a basis for taking management
action. In the absence of such information, the BRT was restricted to a
largely species by species consideration of the data.
The status review for Puget Sound Pacific hake, Pacific cod, and walleye pollock was conducted by a team of researchers from the National Marine Fisheries Service's (NMFS) Northwest Fisheries Science Center (NWFSC) and Alaska Fisheries Science Center (AKFSC). This biological review team (BRT) relied on comments and informational reports submitted by the public and by state, tribal, and federal agencies (technical terms and abbreviations such as "BRT" are defined in the Glossary). The majority of the Pacific hake extinction risk assessment analyses are the contribution of Dr. William H. Lenarz. The authors acknowledge the efforts of all who contributed to this record, especially the Washington Department of Fish and Wildlife.
Numerous individual fishery scientists and managers provided information that aided in the preparation of this document and deserve special thanks. We particularly wish to thank Wayne Palsson from the Washington Department of Fish and Wildlife for updated information, data, opinions, and advice. Others who provided significant contributions to this effort include: Greg Bargmann, Jim West, and Steve Jeffries from WDFW; and Robert DeLong, Jeff Laake, and Patrick Gearin of NMFS' National Marine Mammal Laboratory (NMML).
At the NMML, we also want to thank Doug DeMaster, Robert DeLong, and others for reviewing (on a tight time-line) the preliminary risk assessment of pinniped predation on Pacific hake in the Port Susan population. An early draft of this document was critically reviewed by Craig Bowhay of the Northwest Indian Fisheries Commission; Wayne Palsson, Dr. Jack Tagart, and Greg Bargmann of WDFW; and Sandy McFarlane of the Department of Fisheries and Oceans Canada. We thank them for their comments and suggestions.
Kathleen Neely of the NWFSC provided graphical assistance with a number of the figures included in this report.
The BRT for Puget Sound Pacific
hake, Pacific cod, and walleye pollock consisted of the following members:
from the Northwest Fisheries Science Center, Tonya L. Builder, Dr. W. Stewart
Grant, Dr. Richard G. Gustafson, Lyndal L. Johnson, Dr. Bruce B. McCain,
Dr. Richard D. Methot, Cyreis Schmitt, Dr. Thomas C. Wainwright, and Dr.
Robin Waples; and from the Alaska Fisheries Science Center, Dr. Kevin M.
Bailey, Michael Canino, Dr. Martin W. Dorn, Dr. Charles Fowler, and Dr.
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