Fecundity and egg size variation in North American Pacific salmon (Oncorhynchus)

Abstract

We examined regional and latitudinal variation in fecundity and egg weight for five species of Pacific salmon (Oncorhynchus) along the Pacific coast of North America. Data were examined for 24 chum salmon, 15 pink salmon, 34 sockeye salmon, 44 chinook salmon, and 40 coho salmon populations from published sources, unpublished Canadian hatchery records, our own laboratory investigations, and other unpublished sources. Substantial regional variation in fecundity and egg weight was observed, with salmon on the Queen Charlotte Islands and Vancouver Island in British Columbia generally having lower fecundity and larger egg size than nearby mainland populations. The relative distance of freshwater migration to the spawning grounds generally had a marked effect on both fecundity and egg size, with populations spawning in the upper portions in the drainages of large rivers like the Fraser River in British Columbia having reduced fecundity and egg size compared with coastal spawning populations. Fecundity was generally higher and egg size generally lower in more northern populations of sockeye, chinook, and coho salmon compared with southern ones. We suggest that egg size tends to be lower in northern populations of some species as a result of increased fecundity due to their older ages at maturity and a limited amount of energy that can be expended on egg production.

Science Advancements Key to Increasing Management Value of Life Stage Monitoring Networks for Endangered Sacramento River Winter-Run Chinook Salmon in California

“…Many salmonid stocks are thought to be buffered from demographic stochasticity through risk being spread across different cohorts that can mature and spawn in mixed-age classes (Greene et al 2010;). In addition, the presence of a significant number of age-4 spawners could positively influence SRWRC productivity through increases in fecundity common to larger females (Beacham and Murray 1993). However, maturation rates and age structure diversity among the evolutionarily significant units (ESUs) of Central Valley salmon vary, with SRWRC expressing the lowest diversity (Fisher 1994;Satterthwaite et al 2017).…”

There and back again: migration in freshwater fishes

“…This is especially important for migrants with a semelparous life history, such as Pacific salmon, because they die after reproduction and thus achieve their total lifetime fitness via this single reproductive event. In addition to direct mortality, migratory costs may also be manifested as decreased fecundity and studies have reported negative correlations between fecundity and migration distance in several fish species (e.g., Beacham and Murray 1993;Kinnison et al 2001;Crossin et al 2004). More evidence in support of the idea that demanding migrations have negative impact on fitness parameters comes from a study involving numerous resident and migratory populations of brown trout (Salmo trutta L., 1758).…”

Comment on "Rapid Evolution of Egg Size in Captive Salmon" (II)

“…1). After accounting for both regime shifts and the fact that female length and egg size are correlated in salmon (4,5) b , where E s is the standardized egg size, E o is the observed egg size, L m is the mean female length in the population, L o is the observed length in a particular year, and b is the regression coefficient of the ln E o on ln L o in each regime in each population. Egg size data in each regime in each population were standardized separately to the overall mean length in each population.…”