Salmon Species & Estuary Use
Some salmon species pass through nearshore waters quickly on their way to sea. Others may spend months in estuaries, feeding, growing, and adjusting to salt water. A lot depends on the size of the salmon when it reaches the estuary. In general, larger salmon such as sockeye, coho and chinook yearlings are less dependent on estuaries and may pass through relatively rapidly. Smaller salmon such as chum, pink, and chinook fry and fingerlings may use estuaries and nearshore waters for up to 180 days.
Pacific Salmon Species
Of all Pacific salmon species, "ocean-type" (fall) chinook rely most on estuaries and nearshore waters along Puget Sound - some stay as long as 189 days. Chinook fry and fingerlings move downstream to estuaries at a young age. Here they adapt to saltwater, hide from predators, and grow rapidly feeding on planktonic animals.
Chum fry travel downstream shortly after hatching, form dense schools, and spend a month or more in estuary waters. Young chum favor eelgrass meadows and often prey on small crustaceans such as harpacticoid copepods, gammarid amphipods, and isopods. Many genetically distinct runs exist on Puget Sound and Hood Canal. As many as three distinct populations may exist on the same river, passing through estuaries and on to sea at different rates.
Sockeye spend one or two years developing in lakes. Large smolts typically pass quickly through estuary waters for ocean rearing grounds. One type of sockeye, however, migrates quickly down to estuaries and develops there over time.
Pink salmon begin migrating downstream almost immediately after emerging from the gravel. Pinks move rapidly into tidal channels and nearshore nursery areas, often in schools and usually in darkness. Juvenile pinks grow quickly while in nearshore waters, up to 5-6% body weight per day. Preferred prey of young pinks includes small crustaceans (euphausids, amphipods, and cladocerans). After a few weeks to a few months in estuaries and nearshore regions, pink salmon move offshore, where they migrate at sea for 12-16 months.
When coho enter estuary waters, they may be two years old and relatively large. As larger smolts, coho may pass quickly through estuaries and out to sea. In some cases however, the transition to the ocean may be prolonged. Some coho never leave coastal waters and return early to spawn as immature "jacks." Another "ocean type" coho migrates as fry to brackish waters in estuaries. These juveniles may use tidal sloughs and flood plains for development.
Recently designated the same genus as Pacific salmon, steelhead are large rainbow trout that go to sea. Young steelhead spend two to three years in streams developing. In estuaries, larger smolts feed on insects, small crustaceans, and crab larvae. Studies show that steelhead from the Puget Sound area are genetically distinct from other regions. There may also be some genetic differentiation between populations from northern and southern Puget Sound. Even when Puget Sound steelhead migrate to the ocean, they may spend considerable time as juveniles or adults in the protected waters of the Sound.
Oncorhynchus clarki clarki
Recently designated the same genus as Pacific salmon, cutthroat can be found year round in shallow water close to shore. Juvenile cutthroat trout spend a range of times in estuaries. Some cutthroat trout may remain in nearshore/estuary waters most of their lives feeding on amphipods, isopods, shrimp, and young fish such as pink and chum salmon.
Source: Salmon and Steelhead Stock Inventory, Washington Department of Fish and Wildlife, 1993. Fish images courtesy Washington Department of Fish and Wildlife.
Puget Sound Nearshore Environments: Salmon Use, Large River Mouth, King County Department of Natural Resources. A color illustration showing zones used by juvenile salmon.
Anadromous Fish Life History Profiles, Pacific States Marine Fisheries Commission. Anadromous fish species that inhabit the Pacific Northwest including salmon.
Wild Salmon: Our Precious Natural Resource, Washington State Department of Fish & Wildlife. Salmon/Steelhead species information.
Salmon & Steelhead, NOAA Fisheries Northwest Regional Office. Salmon information & programs, publications & resources, regulations & laws.
Puget Sound Chinook Salmon ESU, NOAA Fisheries Northwest Regional Office. ESA listing status.
Comments? E-mail: Shellyne Grisham