Stable isotopes and gut content show diet overlap among native and introduced piscivores in a large oligotrophic lake
Bibliographic record
Abstract
Abstract – In past dietary studies kokanee Oncorhynchus nerka were prominent in the diet of Pend Oreille Lake's large piscivores: native bull trout Salvelinus confluentus, cutthroat trout O. clarki and northern pikeminnow Ptychocheilus oregonensis, and introduced lake trout S. namaycush and Kamloops rainbow trout O. mykiss gairdneri. However, kokanee have declined to 10–20% of their former abundance. We therefore initiated this study to understand current predation demands on kokanee and diet overlap among piscivores, using gut content samples and analysis of stable nitrogen (δ15N) and carbon (δ13C) isotopes from the lake's fish and invertebrate community. In gut content samples, kokanee were the main prey item of large [i.e., ≥400 mm total length (TL)] bull and lake trout; a conclusion that was affirmed by stable isotope analysis. Rainbow trout >500 mm TL consumed mostly kokanee, thus there was a high degree of diet overlap among large bull, lake and rainbow trout. Small (i.e., <400 mm TL) rainbow and cutthroat trout diets overlapped, and were composed mostly of littoral benthic invertebrates. However, gut content and stable isotope analysis did not accord for 400–500 mm TL rainbow trout, small lake trout, and large cutthroat trout. In these instances, a linear mixing model using stable isotope results predicted kokanee consumption for each species, but no kokanee were identified in rainbow or lake trout gut content. Gut content and stable isotope analysis of native northern pikeminnow indicated a diet of mostly littoral benthic invertebrates at smaller (100–150 mm TL) lengths, with kokanee becoming more prominent in the diet of individuals >300 mm TL. Percent of kokanee in the diet of northern pikeminnow has declined from a prior study; otherwise piscivore diets have apparently remained unchanged. In this study, judgments as to the feeding of some piscvores, based on gut content alone, would be tenuous because of small sample sizes, but stable isotope analysis provided an efficient means for confirming diets.
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".