The decline in abundance and body length of Chum Salmon in the Fishing Branch River, Yukon
Bibliographic record
Abstract
ABSTRACT Objective Numerous populations of Pacific salmon have experienced decreased abundance and body size in the past 50 years. Ni’iinlii Njik (Fishing Branch River) in northern Yukon is the natal stream to the largest population of Chum Salmon Oncorhynchus keta in northern Canada. For over 50 years, total spawner abundance, age, sex and fork length data were collected from thousands of spawning Chum Salmon. We asked whether there were systematic changes in the body length, age, and sex ratio of spawning Chum Salmon from this population over this time frame. Methods Age, sex, and fork length were sampled from 23,906 spawning Chum Salmon, and total spawner abundance was counted over 50 years (1972–2022) from the Fishing Branch River, a tributary of the Yukon River and natal stream to the largest Chum Salmon population in northern Canada. Results Total spawner abundance has decreased significantly since the 1970s, and the average fork length of females and males declined 3.1% and 3.6%, respectively. This statistically significant decline in average length was associated with significant reductions in length at age of 4- and 5-year-old fish. Age-3 females and 6-year-old fish did not have significant declines, though they are much smaller components of the age structure. There is some indication that Chum Salmon are also maturing to spawn at earlier ages in this population, with age-4 fish increasing in relative abundance. The average age of spawners decreased from 4.6 to 4.3 years for male fish and from 4.5 to 4.2 years for female fish. These declines parallel other documented declines in body length and age of salmon in the North Pacific Ocean. Conclusions Causes for body size and abundance declines may include changing marine conditions and increased competition from hatchery and wild Pink Salmon Oncorhynchus gorbuscha and Chum Salmon across the North Pacific Ocean. Decreased body length translates into lower per-capita reproductive output, and management strategies that do not incorporate these shifting demographic characteristics may have detrimental consequences on future abundance and productivity of Chum Salmon in this and other ecosystems.
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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 | 0.001 | 0.001 |
| 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".