Mortality of migrating Pacific salmon smolts in southern British Columbia, Canada
Bibliographic record
Abstract
Determination of causes for recent declines in marine survival rates of many Pacific salmon populations has been hindered by lack of information on where and when mortality predominantly occurs. Acoustic telemetry was used to monitor movements of tagged outmigrating juvenile salmon, and mark-recapture models were used to estimate survival. Several methods were developed for estimating detection probabilities (p) of tagged fish: models for combining multiple populations with partially-overlapping migration routes allowed for sharing of information among populations to compensate for small sample sizes; models for estimating p using only local information at detection stations reliably predicted mark-recapture p at large sample sizes; estimated p during mobile transect surveys attenuated from transect lines and depended on boat speed; variation among tags in acoustic strength resulted in minor heterogeneity in p; and p estimates derived from test tag passes were used to estimate freshwater residualization rates. Migration patterns varied among species, with steelhead and sockeye salmon quickly leaving Georgia Strait, and coho and Chinook salmon instead likely residing in the inshore Strait during summer months, thereby confounding interpretation of early ocean mortality. High mortality often occurred before ocean entry. Variation in survival during the downstream and inshore coastal migration was largely attributed to size-selective mortality against smaller fish and variation in migration distance or travel time. Some components of mortality during the downstream and inshore migration were independent of distance travelled, suggesting high mortality periods soon after release in freshwater and soon after ocean entry. Compared to wild conspecifics, hatchery-reared steelhead suffered high mortality immediately after release, and this survival difference was maintained through the inshore migration. In an experiment to test the effect of solar ultraviolet radiation during freshwater rearing on smolt mortality, no survival differences were observed between UV-shaded and UV-exposed treatment groups of coho or sockeye salmon. Overall, instantaneous mortality rates (time-based or distance-based) were highest soon after release, declined during the inshore migration, and were lowest for the remainder of smolt-to-adult ocean life, supporting hypotheses of high mortality early in the migration but not ruling out hypotheses of high mortality during the first marine winter.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.002 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".