V. B. 3. Groundfish |
Groundfish, which include rockfish species, live in marine waters and spend their lives near or on the bottom. In Washington State, groundfish are legally defined as food fishes, and most are the focus of important fisheries (Palsson et al. 1997). Although many adult groundfish reside within the deeper waters of Puget Sound, many/most rely on shallow nearshore marine and estuarine habitats during part of their life history (Williams and Thom 2001) (Table V-6). Groundfish in nearshore marine and estuarine areas of Bainbridge Island are considered a component of South Puget Sound stocks (Palsson et al. 1997).
Table V-6. Summary of Nearshore Marine Habitat Use by Important Groundfish Species in Washington State (from Williams et al. 2001).
Nearshore Marine Use
|
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| Common Name | Scientific Name | Adult Spawning |
Residence &Migration |
Juvenile Rearing |
| Pacific Cod | Gadus macrocephalus | l |
l |
|
| Walleye Pollock | Theragra chalcogramma | l |
l |
|
| Pacific Hake | Merluccius productus | l |
l |
|
| Lingcod | Ophiodon elongatus | l |
l |
l |
| English Sole | Pleuronectes vetulus | l |
l |
|
| Rock Sole | Lepidopsetta bilineata | l |
l |
l |
| Brown Rockfish | Sebastes auriculatus | l |
l |
l |
| Copper Rockfish | Sebastes caurinus | l |
l |
l |
| Quillback Rockfish | Sebastes maliger | l |
l |
l |
Changing water temperatures, decreases in prey availability, marine mammal predation, as well as overharvest are considered the primary stressors to groundfish species. Pacific cod, walleye pollock, and Pacific hake are short lived and susceptible to overfishing that reduces age class diversity and abundance; stocks are then susceptible to collapse during years of naturally poor recruitment (West 1997). English sole in contaminated areas of Puget Sound exhibit high rates of disease, increased parasite loads, and impaired reproductive success (Schmitt et al. 1994). Similarly, shoreline development has altered intertidal spawning beaches for rock sole. Rockfishes are susceptible to the loss of critical nearshore habitat for settlement, feeding, and refuge and are likely susceptible to fragmentation of the links between nearshore marine habitats that are critical to various life history stages (Williams et al. 2001). Losses and alteration of shallow nearshore habitats throughout Puget Sound may affect juvenile stages of all species, but have generally not been considered in the literature.
Specific information follows on the general nearshore ecology, habitat functional requirements, and Bainbridge Island distribution of selected groundfish species.
Pacific Cod (Gadus macrocephalus)
In late summer, juvenile Pacific cod metamorphose from their larval stage and settle in shallow vegetated habitats (eelgrass beds and macroalgae) where they find shelter and prey resources, which include copepods, amphipods and mysids (Matthews 1989). Adults concentrate in shallow embayments during the winter to spawn before dispersing to deeper waters to feed during the remainder of the year (Williams et al. 2001) (Figure V-8). A distinct stock of Pacific cod existed historically in South Puget Sound, centered around Agate Pass spawning grounds (West 1997). This stock, considered the southern limit of fishery-exploitable populations, once supported commercial fisheries before precipitous declines in catches during the 1980s (Palsson 1990; Schmitt et al. 1994; Palsson et al. 1997). Currently, Pacific cod populations in South Puget Sound are considered of “critical” status (Puget Sound Water Quality Action Team 2002) (Table V-1).
Figure V-8. Pacific cod (Gadus macrocephalus) (from Hart 1988).
Walleye Pollock (Theragra chalcogramma)
Juvenile walleye pollock settle near the bottom and then migrate inshore to eelgrass and shallow gravel and cobble habitats for their first year (Williams et al. 2001). Juvenile pollock feed primarily on small crustaceans (mysids, calanoid and harpacticoid copepods, gammarid amphipods, and juvenile shrimp), progressing to small fishes as they grow larger. Adult walleye pollock inhabit midwater or nearbottom cold-water environments and form spawning aggregations from February to April in localized deep water areas (Schmitt et al. 1994). Walleye pollock in South Puget Sound have experienced severe declines in recent years and are considered of “critical” status (Palsson et al. 1997) (West 1997) (Table V-1).
Pacific Hake (Merluccius productus)
Juvenile and immature Pacific hake may aggregate in inshore waters and mainland inlets, where they feed and grow away from concentrations of adults (Schmitt et al. 1994). Spawning occurs from March to May at mid-water depths of 50 to 350 m. They are opportunistic carnivores and feed primarily on small forage fishes. A small genetically distinct resident hake population in southern Puget Sound migrates seasonally between Port Susan and Saratoga Passage. Currently, the status of Pacific hake in South Puget Sound is considered “critical” because of the sharp decline in abundance observed in annual hydro-acoustic surveys (Palsson et al. 1997) (Table V-1)(West 1997). Pacific hake have been retained as a candidate species for ESA listing pending further genetic and other studies.
Lingcod (Ophiodon elongatus)
Juvenile lingcod move to benthic habitats in late spring-early summer, settling in shallow water, vegetated (kelp or eelgrass) habitats (Buckley et al. 1984; Cass et al. 1990). Age 1-2+ juveniles are commonly observed in high-current, soft-bottom, or shell-hash habitats near the mouths of bays and estuaries (Doty 1993). Juvenile and adults are carnivorous, feeding on crustaceans and fishes (Emmett et al. 1991). Lingcod are typically associated with rocky reefs or other complex substrata with high current velocities and are found throughout Puget Sound, including Bainbridge Island (West 1997). They are considered nonmigratory, with mostly self-replenishing local stocks (Cass et al. 1990). They are found from the intertidal zone to 200 m, but are most abundant at depths between 10 and 100 m. Adult lingcod spawn between December and March, laying adhesive eggs in nests found in rocky crevices in shallow areas with strong water circulation. Lingcod catches have steadily and substantially declined in Puget Sound since the early 1980s, primarily due to overharvest (West 1997). However, the most recent assessment for South Puget Sound suggests that lingcod populations are at above average levels (Puget Sound Water Quality Action Team 2002) (Table V-1).
English Sole (Pleuronectes vetulus)
Juvenile and larval English sole distribution patterns suggest active migration or directed transport to estuary or shallow nearshore marine areas for settlement between March and May (Shreffler 1995). After metamorphosis, they remain in protected coastal and estuarine areas where they feed on abundant prey resources. Juvenile English sole use a variety of shallow nearshore marine and estuarine habitats, but tend to prefer shallow (<12 m deep) mud and sand substrates in Puget Sound (Emmett et al. 1991). Juveniles exhibit distinct patterns of depth segregation, with smaller fish generally restricted to shallow waters and larger fish being found progressively deeper. They are opportunistic benthic carnivores, feeding on harpacticoid copepods, gammarid amphipods, polychaetes, small bivalves and siphons, and cumaceans (Emmett et al. 1991; Williams 1994). Adult English sole occur over flat-bottom coastal habitats, primarily at shallow depths during the summer and down to 250 m during the winter (Schmitt et al. 1994). English sole in central Puget Sound exhibit significant homing and tend to remain within localized geographic regions. They are currently found throughout most soft-bottom habitats in Puget Sound, including Bainbridge Island. Recreational catch rates of English sole and trawl survey data indicate the adult population is at below-average levels in South Puget Sound (Palsson et al. 1997) (Table V-1).
Rock Sole (Lepidopsetta bilineata)
Rock sole are a right-eyed flatfish commonly found throughout Puget Sound, primarily over cobble, gravel, and sand substrates. Juveniles and adults are abundant in nearshore marine habitats at depths <15 m (Donnelly et al. 1984). Rock sole feed on molluscs, polychaete worms, crustaceans, brittle stars, and fishes (Simenstad et al. 1979). Adults spawn on upper intertidal beaches, but may also spawn at subtidal depths as well (Penttila 1995). Documented intertidal rock sole spawning is relatively infrequent and largely confined to the region south of Seattle. Rock sole are one of the more common flatfishes harvested by recreational anglers, and catch trends indicate that stocks in South Puget Sound, which includes Bainbridge Island, are at average levels (Palsson et al. 1997) (Table V-1).
Rockfish (Sebastes spp.)
Over 20 species of rockfish inhabit Puget Sound, but only three, copper, quillback, and brown rockfish, are commonly caught by recreational fisheries in nearshore marine habitats of Central and South Puget Sound (West 1997). Within Puget Sound, juvenile rockfish settle initially into shallow, vegetated habitats of bull kelp, macroalgae and eelgrass during their first year (Doty et al. 1995). They are commonly found in nearshore habitats throughout the summer and fall. Upon reaching adult size, rockfish move to rocky reefs, boulders, offshore pinnacles, and other hard, high relief substrates (Matthews 1989). Most species are relatively sedentary and generally do not venture over 30 m2 from preferred high-relief habitat (West 1997). Rockfish generally display slow growth, late maturation (>4 years), and long life spans; females’ fecundity (reproductive capacity) increases with increasing size. Rockfish may be locally abundant in some locations in Puget Sound, but are prone to severe depletion from overfishing due to their habitat specificity (West 1997). Currently, copper, quillback, and brown rockfish populations in both north and south Puget Sound, including Bainbridge Island, are characterized as “depressed” (Puget Sound Water Quality Action Team 2000b) (Table V-1). A more recent federal status review of Puget Sound stocks concluded that none of these species are at risk of extinction, but the level of available information leaves substantial uncertainty in this determination (Stout et al. 2001b).
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