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Chapter 5 -- Anadromous Salmonids and Their Habitats (continued)

Life History Patterns of Anadromous Salmonids

Steelhead

Of the salmonid species of the Smith River (Table 28), steelhead (Oncorhynchus mykiss) are the most abundant (Reedy 1995, Huntington et al. 1996) and have the greatest diversity of life history patterns. In the Smith River, adult steelhead migrate primarily in the fall or winter, although there is a spring-run population that is currently depressed. The historic size of the spring run of steelhead in the Smith River is not known (Waldvogel personal communication 1996). Spring-run steelhead are also known as "summer steelhead".

 

Table 28. Known and suspected life history patterns of anadromous salmonids in the Smith River.

 

Species

 

Stock

Freshwater rearing

Estuary rearing

Ocean residence

Upstream migration timing

Steelhead

Winter run

2-3 years

Adaptation to salt water

1-5 years

November to March

 

"Blue backs"

"

?

1-2 years

March to April

 

Spring run

"

?

1-3 years

April to May

Chinook

Fall runs

(in three pulses)

3-6 months

3-4 months

 

1-5 years

September to February

 

Spring run

3 mo. to 1 yr

3-5 months

1-4 years

April to June

Coho

Yearling smolt

1 year

A few weeks

1-2 years

Nov to Jan

 

(subyrling smolt?)

(7-8 mo??)

"

"

"

Chum

 

A few weeks

1-2 months

1-4 years

December

Coastal cutthroat

 

2-3 years

A few weeks

1-3 years

May to Nov.

 

Steelhead have greater swimming and leaping abilities than chinook or coho (Bjornn and Reiser 1991, Table 31) and can access and utilize steeper streams (Trush 1995). Therefore, steelhead tend to spawn in streams higher in the watershed. Steelhead also prefer smaller gravel than chinook or coho. They stray more than other anadromous species and may migrate up and down several tributaries. Unlike chinook and coho, steelhead adults may migrate, spawn, and return to the ocean several times. In coastal streams, up to 30% of adult steelhead survive to spawn more than once (Meehan and Bjornn 1991).

Steelhead fry emerge in the spring and rear in freshwater for one to three years, although two years is most common. This species (Oncorhynchus mykiss) includes "rainbow trout" that complete their entire life cycle in freshwater as well as ocean-run steelhead. Steelhead smolts generally migrate to the ocean in spring. Typically, larger members of an age class migrate downstream and smaller ones remain in the river. This behavior is probably related to the higher survival of large smolts in the ocean. Some young-of-the-year steelhead discontinue emigrating and reside in the river all summer and winter (Reedy 1995).

Some steelhead, both male and female, return to their natal stream after only two to four months in the ocean. These "half-pounders" are from 12 to 16 inches long and may or may not be viable spawners during this life stage. The Smith River also supports a distinct run of steelhead "blue backs" in late winter (Waldvogel personal communication 1996).

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