The National Marine Fisheries Service (NMFS) received a petition on February 8, 1999 to list 18 species of marine fishes in Puget Sound under the U.S. Endangered Species Act (ESA) (Wright 1999). The ESA allows the listing of "distinct population segments" of vertebrate species or subspecies as threatened or endangered, if severe declines in abundance are indicated or substantial risks are facing the species. NMFS evaluated the petition for each species to determine whether the petitioner provided "substantial information" as required by the ESA to list a species. The agency also reviewed other readily available information and consulted with state and tribal biologists to determine whether general agreement existed on the uniqueness, distribution, abundance, and threats to the petitioned species/populations. Additionally, NMFS evaluated whether available information might support the identification of distinct population segments that might warrant listing under the ESA. NMFS (1999) concluded that the petitioner provided substantial information, or cited such information in other sources, to initiate a status review for Pacific hake, Merluccius productus (Ayres, 1855); Pacific cod, Gadus macrocephalus Tilesius, 1810; walleye pollock, Theragra chalcogramma (Pallas, 1815); and Pacific herring, Clupea pallasi Valenciennes, 1847. NMFS (1999) further concluded that the information provided in the petition on Puget Sound rockfish species was insubstantial for most of the species petitioned, but that compelling reasons existed to believe some Puget Sound rockfishes may warrant ESA protection. Information appeared to be sufficient to conduct a status review that could provide the basis for an ESA determination for three species: brown rockfish, Sebastes auriculatus Girard, 1854; copper rockfish, S. caurinus Richardson, 1845; and quillback rockfish, S. maliger Jordan and Gilbert, 1880. NMFS (1999) decided, therefore, to also initiate status reviews for these three species of Puget Sound rockfish. NMFS determined that it would be most efficient to conduct these status reviews along taxonomic lines, and therefore three BRTs were formed, one for the gadiforms, one for rockfish, and one for Pacific herring.
This document reports the results of a comprehensive ESA status review of three gadiform species in Puget Sound: Pacific hake, Pacific cod, and walleye pollock. Hake species in the genus Merluccius are variously placed by different authorities in the Family Merluccidae (Cohen et al. 1990, Eschmeyer 1998) or the Family Gadidae (Robins et al. 1991) (together with Pacific cod and walleye pollock). In either taxonomic arrangement, the three species are members of the Order Gadiformes (Cohen et al. 1990, Robins et al. 1991, Eschmeyer 1998), and for the purposes of this document will hereafter be jointly referred to as gadiforms. Biological and ecological information for populations throughout the range of the three gadiform species were also considered in order to provide a context for evaluating information on these species within Puget Sound.
In order to meet the provision in the ESA that listing determinations be made with the best available scientific and commercial information, NMFS formed a team of scientists with diverse backgrounds in marine fish biology and marine habitats to conduct this review. This Biological Review Team (BRT)[1] reviewed and evaluated scientific information compiled by NMFS staff from published literature and unpublished data. Information presented at public meetings in 1999 in Seattle, Washington was also considered. The BRT also reviewed additional information submitted to the ESA administrative record.
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)? These questions are addressed for each of the three species in the following separate sections. If it is determined that a listing(s) is warranted, then NMFS is required by law (1973 ESA Sec. 4(a)(1)) to identify one or more of the following factors responsible for the species' threatened or endangered status: 1) destruction or modification of habitat, 2) over-utilization by humans, 3) disease or predation, 4) inadequacy of existing regulatory mechanisms, or 5) other natural or human factors. This status review does not formally address factors for decline, except as they provide information about the degree of risk faced by the species in the future, if present conditions prevail.
The ESA, as originally enacted, defined "species" to include "any subspecies of fish or wildlife or plants and any other group of fish or wildlife of the same species or smaller taxa in common spatial arrangement that interbreed when mature." As amended in 1978, the ESA defined "species" as "any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature." Thus the ability to list distinct population segments (DPSs) is restricted to vertebrate animals, and specifically excludes plants and invertebrates. Furthermore, Congress has stated that the authority to list DPSs should be used "sparingly and only when the biological evidence indicates that such action is warranted" (Senate Report 151, 96th Congress, 1st Session, 1979). Listing of vertebrate DPSs has occurred relatively rarely, for example, USFWS-NMFS (1996) stated that "of over 300 native vertebrate species listed under the Act, only about 30 are given separate status as DPS's." Wilcove et al. (1993) examined listings under the ESA between 1985 and 1991 and found that only 8.5% of the 94 vertebrate "species" listed or proposed for listing were classified as DPSs.
Guidance on what constitutes a "distinct population segment" is provided by the joint U.S. Fish and Wildlife Service (USFWS) and NMFS interagency policy on vertebrate populations (USFWS-NMFS 1996). To be considered "distinct," a population, or group of populations, must be "discrete" from other populations and "significant" to the species as a whole. A population segment of a vertebrate species may be considered discrete if it is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors. The policy states that quantitative measures of genetic or morphological discontinuity may provide evidence of this separation. If a population segment is considered discrete, considerations that can be used to determine its significance to the taxon as a whole include: 1) persistence of the discrete population segment in an ecological setting unusual or unique for the taxon, 2) evidence that loss of the discrete population segment would result in a significant gap in the range of the taxon, 3) evidence that the discrete population segment represents the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historic range, and 4) evidence that the discrete population segment differs markedly from other populations of the species in its genetic characteristics.
This joint policy applies to all vertebrate species, but does not elaborate on the information that can be used to assess distinctiveness in species of marine fishes. The types of evidence that can be considered to evaluate distinctiveness of populations in Pacific salmon species have been extensively reviewed (Waples 1991a, b, 1995), and similar kinds of evidence can be used to assess distinctiveness of populations or groups of populations of marine fishes. NMFS Pacific salmon framework advocates a holistic approach in which all available information is considered, as well as a consideration of the strengths and limitations of such information in delineating distinct population segments. Important information includes natural rates of migration and recolonization, evaluations of the efficacy of natural barriers to migration, phenotypic and life history traits that reflect local adaptation, and measurements of genetic differences between populations. NMFS's Pacific salmon policy states that (Waples 1995, p. 9):
A vertebrate population will be considered distinct (and hence a "species") for purposes of conservation under the Act if the population represents an evolutionarily significant unit (ESU) of the biological species. An ESU is a population (or group of populations) that (1) is substantially reproductively isolated from other conspecific population units, and (2) represents an important component in the evolutionary legacy of the species.
To date, NMFS has used the Pacific salmon policy to identify over 50 ESUs among seven biological species of anadromous Pacific salmonids (Busby et al. 1993, 1994, 1996; Gustafson et al. 1997; Hard et al. 1996; Johnson et al. 1991, 1994, 1997, 1999; Matthews and Waples 1991; Myers et al. 1998; Waknitz et al. 1995; Waples et al. 1991a, b; Weitkamp et al. 1995). Approximately half of these ESUs have been listed as threatened or endangered species (see http://www.nwr.noaa.gov/ for a complete list, and the current status of Pacific salmon ESUs). Although the joint DPS policy does not specifically identify evolutionary significance as a criterion for distinctness, "the first criterion (discreteness) is similar to the reproductive isolation criterion in the NMFS [Pacific] salmon policy, and the second (significance to the biological species) is roughly analogous to the contribution to ecological-genetic diversity criterion of the NMFS [Pacific] salmon policy" (Waples 1995, p. 25).
The Natural Resource Council, in a report entitled "Science and the Endangered Species Act" (NRC 1995), developed the concept of an evolutionary unit (EU) to assist in identifying DPSs. This report defined an EU as "a group of organisms that represents a segment of biological diversity that shares evolutionary lineage and contains the potential for a unique evolutionary future" (NRC 1995). NRC (1995) stated that evidence of uniqueness of an EU can be found through analysis of morphology, behavior, physiology, and biochemistry, and that, in most cases, an EU will occupy a particular geographical area. NRC (1995) suggested that a DPS can be thought of as "an evolutionarily distinct population segment that is geographically or otherwise isolated from other population segments." The DPS, in some cases, may be a group of populations (metapopulation, i.e., "a larger population made up of smaller, local breeding populations that have some genetic and ecological interactions among them") (NRC 1995). The considerations identified by the NRC (1995) are very similar to those identified and used by the NMFSs ESU policy.
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." NMFS considers a variety of information in evaluating the level of risk faced by a DPS. Important considerations include 1) absolute numbers of fish and their spatial and temporal distribution, 2) current abundance in relation to historical abundance and carrying capacity of the habitat, 3) trends in abundance, based on catch-per-unit effort (CPUE) or on estimates of spawner-recruit ratios, 4) possible threats to genetic integrity, 5) recent events (e.g., climate variability or change in management) that have predictable short-term consequences for the abundance of the DPS. Additional risk factors, such as disease prevalence or changes in life-history traits, may also be considered in evaluating risk to populations.
The determination of whether a species is threatened or endangered should be made according to the ESA on the basis of the best scientific information available on its current status, after taking into consideration conservation measures that are proposed or are in place. We did not evaluate likely or possible effects of conservation measures in this review. Therefore, we did not recommend whether identified DPSs should be listed as threatened or endangered species, because that determination requires evaluation of additional factors not considered by the BRT. Instead, the BRT drew scientific conclusions about the risk of extinction faced by identified DPSs under the assumption that present conditions would continue and with the recognition that natural demographic and environmental variability is an inherent feature of "present conditions." Conservation measures will be considered by the NMFS Northwest Regional Office in making ESA listing recommendations.
NMFS received on February 8, 1999 a petition from Sam Wright, a biologist retired from the Washington State Department of Fish and Wildlife, to list as threatened or endangered 18 species/populations of marine fishes in Puget Sound, Washington and to designate critical habitat (Wright 1999). NMFS evaluated the petition to determine whether it presented substantial scientific or commercial information indicating that the petitioned action may be warranted. Section 424.14(b)(1) of NMFS' ESA implementation regulations defines "substantial" information" as the amount of information that would lead a reasonable person to believe that the measure proposed in the petition may be warranted. Section 424.14(b)(2) of these regulations lists factors to be considered in evaluating the petition, including whether the petition contains detailed narrative justification for the recommended measure, a description of past and present numbers, of geographical distributions of the species and of threats facing the species.
The petitioner defined a stock as a "population of fish which is reproductively isolated, or partially isolated, from other such populations of the same species." Most of the petitioner's arguments dealt with evidence for reproductive isolation between populations within Puget Sound, and between populations in Puget Sound and those along the outer coast. Three kinds of information were presented to indicate that significant differences among populations may exist.
First, the petitioner argued that genetic differences between northern and southern regions of Puget Sound may be present, because reduced gene flow in some species may result from the physical isolation of north- and south-sound basins by a shallow sill in Admiralty Inlet and by the narrow passage through Deception Pass. The petitioner stated that the northern portion of Puget Sound is "exposed to storms, receives more oceanic water, and contains abundant, often contiguous, rocky reef habitat." The petitioner also stated that the southern portion of Puget Sound is protected from the action of storms, is more influenced by freshwater, and contains fewer rocky reefs than the northern portion. According to the petitioner, complex current patterns in both segments of the sound may also limit dispersal between localities by the entrainment of planktonic larvae in local gyres.
Second, the petitioner presented information on genetic population subdivision for some species. Allele-frequency differences between populations provide evidence for reproductive isolation between some populations.
Third, the petitioner noted the presence of life-history differences between populations or the occurrence of discrete spawning areas for some species. Life-history differences between areas may reflect genetic differences between populations or may be the result of environmental influences on development and growth in the absence of genetic differentiation. The occurrence of discrete spawning areas is a necessary, but not sufficient criterion for the development of reproductive isolation between populations.
Most of the petitioner's assessment of abundances was based on fishery statistics and sporadic stock assessments by the Washington State fishery management agencies. In addition to harvests, the petitioner listed marine mammal predation as a possible threat to populations of marine fishes in Puget Sound.
Populations of Pacific hake in Puget Sound lie in the northern part of the geographical range of this species. Outer coastal populations appear to consist of a single large population that migrates annually from winter spawning grounds off California to northern feeding areas in summer. According to the petitioner, a comparison of Pacific hake from Puget Sound, Strait of Juan de Fuca, and coastal Washington demonstrated allele-frequency differences between coastal populations and populations in the Strait of Juan de Fuca and Puget Sound.
According to the petitioner, two major stocks of Pacific hake occur in Puget Sound-a northern spawning aggregation in the Bellingham area, and a southern stock with spawning aggregations in Port Susan. The petitioner stated that as much as 15 million pounds of spawning Pacific hake were once harvested in southern Puget Sound, but the catch declined rapidly after a peak catch in 1983. By 1991, the fishery was closed because of low abundances. According to the petitioner, at peak abundances, acoustic and midwater trawl surveys in winter indicated a spawner biomass of over 40 million pounds, which declined to about one million pounds between 1982 and 1993. The annual exploitation rate in the 1980s was as high as 40% of the adult population. Parallel to the decline in biomass, the average size of individual fish declined so that the stock could not be used commercially. According to the petitioner, predation from marine mammals now appears to be preventing the recovery of this stock.
Pacific cod in Puget Sound lie at the southern margin of the geographical range of this species. The petitioner noted that life-history data for Pacific cod may distinguish coastal populations from populations in Puget Sound and may also distinguish populations within Puget Sound. Puget Sound populations appear to have higher rates of growth and egg production than do other populations along the Pacific Coast. The petitioner stated that within Puget Sound, fishery patterns, the locations of spawning, parasite markers, and tagging studies indicate the existence of three population groups: 1) one located in the Strait of Georgia and the area around Bellingham, 2) one in eastern Strait of Juan de Fuca and Port Townsend Bay, and 3) one in the area south of Admiralty Inlet, including Hood Canal, Agate Passage, and Dalco Passage.
The petitioner noted that the Pacific cod fishery in northern Puget Sound (Kilisut Harbor and Port Townsend Bay spawning stocks) expanded in the late 1970s and early 1980s, but declined in the mid 1980s. The fishery in this area was closed in 1987. However, trawling for Pacific cod in Admiralty Inlet continued until 1994. Experimental trawling in Port Townsend Bay in 1988 failed to find appreciable numbers of Pacific cod. A second spawning Pacific cod population in Agate Passage was the target of a recreational fishery in the 1970s and early 1980s, but declined in the mid 1980s. Few fish were harvested by 1988, and the area was closed to fishing in winter, beginning in 1991. In 1991, this fishery was closed throughout the year. According to the petitioner, acoustic surveys have failed to detect Pacific cod aggregations in surveys of Agate Passage after 1988.
Populations of walleye pollock in Puget Sound lie at the southern margin of the geographical range of this species in the Eastern North Pacific. The petitioner stated that individual walleye pollock grow at different rates in northern and southern areas in Puget Sound, and spawning populations in these two areas are spatially separated.
According to the petitioner, walleye pollock stocks in southern Puget Sound are most at risk of extinction. The petitioner stated that the sports fishery represented the largest catches of walleye pollock in the southern Puget Sound with an average catch exceeding 400,000 pounds per year from 1977 to 1986. Catches declined severely after 1986, and the fishery disappeared by 1989. Trawl surveys were conducted in 1987, 1989, and 1991, and biomasses in these years were estimated to be 3,537, 172, and 99 mt, respectively. The petitioner stated that recent surveys indicate that this stock is severely depressed or may be extinct.
[1]A list of the Biological Review Team members for Pacific hake, Pacific cod, and walleye pollock is included in the acknowledgments section.