Life History and Smolt-to-Adult Survival of Keogh River Steelhead Trout (Salmo gairdneri) and the Relationship to Smolt Size

Abstract

A decade of data on wild steelhead trout (Salmo gairdneri) from a coastal stream in British Columbia demonstrated large fluctuations in smolt number, age structure, size, estimates of adult run sizes, smolt-to-adult survival, and adult age. Adult runs averaged 922 (range 209–2730) with approximately 10% repeat spawning incidence. Females repeat spawned more than males and were more abundant as kelts, but maiden run adults were equally male and female. The proportion of males returning after 1, 2, and 3 yr in the ocean averaged 3, 62, and 35%, respectively; 58 and 42% of females returned after 2 and 3 yr, respectively. Adult age structure, smolt number, and smolt size varied biennially. Adult size decreased with freshwater age, but increased with ocean age of returns. Males were larger at each ocean age. Mean number of smolts (50:50 sex ratio) was 5543 and varied fivefold. Mean smolt length was 173 mm and mean weight was 49 g. Smolts were 2–5 yr old, and freshwater age 3 was most prevalent (average 56%). Mean survival from smolt to adult was 16% (7% from 1978 cohorts to 26% from 1982 cohorts). Survival was positively correlated with smolt length and weight. However, 1982 cohorts had twice the survival of other cohorts, possibly related to El Niño. No clear relationship was found between return age and mean smolt size, but on average, freshwater age was inversely related to ocean age. The relationships suggest that predictive models may be developed over the longer term from this type of study.

Wild chinook salmon survive better than hatchery salmon in a period of poor production

“…A number of studies (Bilton et al 1982;Bilton 1984;Ward and Slaney 1988;Martin and Wertheimer 1989;Ward et al 1989;Henderson and Cass 1991;Beckman et al 1998;Friedland et al 2009) have shown that larger juvenile Pacific salmon survive better in the early marine environment than smaller individuals. Throughout our study, hatchery fish were consistently larger than the better surviving wild chinook salmon.…”

Evaluation of Fish Movements, Migration Patterns, and Population Abundance with Streamwidth PIT Tag Interrogation Systems, Final Report 2002.

“…During the same year we estimated 3,802 steelhead smolts with the SPIs based on 97% (95% CI: 91-97%) efficiency. Similarly, Ward and Slaney (1988) reported smolt abundance estimates of 5,543 from a comparable tributary in British Columbia. Many estimates of smolt abundance are highly variable from year to year, e.g.…”

Anadromy and residency in steelhead and rainbow trout (Oncorhynchus mykiss): a review of the processes and patterns

“…This was due to a general lack of data on the conditional status and demographics of resident O. mykiss, which made it difficult to evaluate the relative effects of individual condition and environment on population-scale life history patterns. Assessing environmental effects on sympatric resident and anadromous populations is challenging because of the great temporal variation in demographics over annual and decadal time scales (Ardren and Kapuscinski 2003;Savvaitova et al 2002;Shapovalov and Taft 1954;Ward and Slaney 1988). Nonetheless, such data are needed to fully understand the amount of life history variation within populations (McPhee et al 2014) and to improve predictive models .…”