Physiological condition and migratory experience affect fitness‐related outcomes in adult female sockeye salmon

Abstract

Relating fish physiology, behaviour and experience to fitness-related outcomes at the individual scale is ecologically significant, but presents difficulties for free-ranging fishes in natural systems. Physiological state (e.g. level of stress or maturity) and experience (e.g. habitat use or exposure to stressors) may alter the probability of survival or reproduction. This study examined the relative influence of physiology and migratory experience on survival, migration duration, reproductive longevity, and egg retention in adult female sockeye salmon (Oncorhynchus nerka) from a Fraser River population.One hundred and thirty-five females were plasma sampled and tagged with radio transmitters and archival temperature loggers. Fish were tracked 55 km through two natal lakes to spawning grounds, following passage of a hydroelectric dam. For 39 females, we assessed the proportion of time within an optimal temperature (T optAS ) window (13.4-19.5°C), which provides ≥90% of maximum aerobic scope. Females with lower plasma glucose concentrations were more likely to reach spawning grounds.Early migrants spent longer in natal lakes. More time in the T optAS window was associated with greater reproductive longevity and lower probability of egg retention. Later arriving females had reduced longevity on spawning grounds, as did females that retained eggs. Exposure to higher dam discharge was associated with reduced reproductive longevity and greater probability of egg retention, but not lower survival, indicating a delayed effect of dam passage. Our results underscore the complexity of factors governing fitness-related outcomes for salmonids, particularly the importance of female experience in the days and weeks prior to spawning. K E Y W O R D Saerobic scope, dam passage, delayed effects, spawning success, thermoregulation

Visible Gill‐Net Injuries Predict Migration and Spawning Failure in Adult Sockeye Salmon

“…Although migration survival was consistent with that in other years, lower survival to spawning was likely due to stressors experienced earlier in the migration (Minke‐Martin et al. ). If our study had been simply based on the migration survival of PIT‐tagged fish (a common endpoint for many biotelemetry studies) and had not included observations of mortalities at the fence and spawning success, the negative combined effects of suboptimal environmental conditions and open fisheries in 2015 would not have been apparent.…”

“…Previous work studying this population has demonstrated that plasma glucose concentration (Minke‐Martin et al. ), anaerobic swimming through fishway attraction flows (Burnett et al. ), and the flow release strategy at Seton Dam (Burnett et al.…”

“…), thermal experience, and Seton Dam discharge (Minke‐Martin et al. ) were associated with survival to spawning. Our application of PIT tagging with minimal biopsy (i.e., DNA sample) precluded the measurement of most of these variables but also provided data with less potential for handling‐related bias and thus more reliable estimates of survival.…”

“…) and spend an average of 10 d in Seton and Anderson lakes before entering Gates Creek (Minke‐Martin et al. ; A. L. Bass, unpublished data). The peak Fraser River entry of Gates Creek Sockeye Salmon occurs in late July, exposing this population to gill‐net fisheries primarily targeting the larger “summer‐run” populations migrating further upstream (entering the Chilcotin, Nechako, and Quesnel rivers).…”

Energetic Status of Alaskan Chinook Salmon: Interpopulation Comparisons and Predictive Modeling Using Bioelectrical Impedance Analysis

“…2004; Quinn ; Minke‐Martin et al. ). Chinook Salmon Oncorhynchus tshawytscha , which must endure longer, more arduous migrations, typically have higher energy content (Quinn ; O'Neill et al.…”