The effect of thermal experience on the survival of sockeye salmon (Oncorhynchus nerka) during their spawning migration in The Fraser River, BC
Bibliographic record
Abstract
,Sockeye salmon (Oncorhynchus nerka) hold tremendous cultural, economic, and ecological value. The Fraser River, in British Columbia supports the largest return of sockeye salmon in Canada. The water temperature in the Fraser River has been increasing in recent decades, with an estimated increase of 1.5°C and 3°C in mean and maximum temperatures, respectively, since the 1950s and a significant increase in the number of days above critical thermal threshold for sockeye salmon. Sockeye salmon are ectotherms, meaning their physiology is highly dependent on their external environment and driven by changes in external temperature. Previous studies have shown that sockeye salmon experience significant impairment and mortality between 18°C and 21°C, and that the impacts of water temperature on survival vary between sexes and populations. Data for this study were collected by LGL Limited, UBC, Kintama, and DFO researchers and their partners. 3265 sockeye salmon were captured and either tagged with radio or acoustic transmitters in 2002, 2003, 2006, 2010, and 2011 and their migration was tracked using receiver arrays. Field-based studies that aim to investigate how water temperature affects survival during the adult spawning migration pose several challenges: 1) what aspect of the thermal experience is assessed, 2) imperfect detection can influence the outcome of studies relying on tagged fish, and 3) populations with small numbers of tagged fish can create unreliable estimates. I aim to address these challenges by 1) comparing the effect of three components of thermal experience, 2) by using an integrated travel time model and state-space version of the Cormack Jolly Seber (CJS) model to differentiate survival and detection, and 3) using a hierarchical mixed effects model to improve the survival probability estimates of populations with low sample sizes. The three aspects of thermal experience that were tested were: 1) the average temperature of the first 10 days following entry into the Fraser River, 2) the moving average of river temperature up to the final detection, and 3) the number of days above 18°C up to the final detection. The best fitting model, of the moving average river temperature prior to the final detection, was selected. The highest overall migration survival probability was found in the Harrison River Conservation Unit (CU), while the lowest overall migration survival probability was estimated in the Anderson-Seton CU. Across all CUs the overall migration survival probability estimate was lower for females than males. Male and female sockeye salmon reached 50% survival probability at ~18.5-20°C and ~18°C-19°C average temperature, respectively. These results align with previous research indicating sockeye salmon survival is significantly impaired between 18°C-21°C. These results also provide evidence to support conservation and enhancement of thermal refuges as well as conservation unit and sex-specific escapement targets and management adjustments.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".