A review and meta‐analysis of growth and life‐history traits of a declining European freshwater fish, crucian carp Carassius carassius
Bibliographic record
Abstract
Abstract In response to reported declines in crucian carp Carassius carassius across Europe, studies of the status and population biology of the species in England led to Biodiversity Action Plan priority designation in the eastern county of Norfolk. In light of new data on crucian carp populations in eastern England (counties of Essex, Hertfordshire and Norfolk), a comprehensive review of available information throughout its native and introduced European range was undertaken to assess the growth and reproduction at a broader scale, thus contributing to conservation and management strategies at a country scale in the UK. For all populations, mean sex ratio was 1:1, back‐calculated total length (TL) ranged from 19 to 334 mm, and maximum age was 13 years. Growth and body condition varied greatly across Europe. Growth trajectories in England, Russia and Poland were significantly faster than in Finland. Within England, growth index was lower in Hertfordshire than in Essex and Norfolk, and Fulton condition (plumpness) index was higher in Essex than in Norfolk. Reproductive traits varied greatly both in males and females, with age at maturity ranging from 1.5 to 5 years, and with the shortest life spans observed in England. Length at maturity was usually at a lower TL in males than females (except in Essex populations). Female age at maturity decreased significantly with juvenile growth, which was defined as TL at age 2, the age above which females in most populations achieved maturity. Predicted temperature rise (i.e. under a climate change scenario) may benefit crucian carp growth, as predicted for related competitive invaders (e.g. goldfish Carassius auratus). From a conservation perspective, suggested management strategies include reducing populations of non‐native fishes, implementing measures of habitat restoration and re‐stocking rehabilitated ponds from ‘source areas’, i.e. those containing crucian carp populations in good status.
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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 | 0.007 | 0.016 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.006 | 0.012 |
| Bibliometrics | 0.009 | 0.010 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".