Trends in Relative Abundance and Early Life Survival of Atlantic Menhaden during 1977–2013 from Long-Term Ichthyoplankton Programs
Bibliographic record
Abstract
The Atlantic Menhaden Brevoortia tyrannus, a commercially important clupeid, supports one of the oldest and largest commercial fisheries on the U.S. East Coast. Despite recent increases in adult biomass, juvenile indices have declined coastwide and have remained particularly low in Chesapeake Bay. In order to understand the underlying causes of this decline, knowledge of larval recruitment is essential. We developed an index of larval abundance by using larval data collected from two large-scale ichthyoplankton sampling programs that occurred from Nova Scotia, Canada, to Cape Hatteras, North Carolina, during 1977–1987 and 1999–2013. Larval abundance data were standardized to a day-0 age by applying an age–length key from a study of larval ingress into Chesapeake Bay; a delta-lognormal model was used to account for spatial and temporal changes in sampling. We found that Atlantic Menhaden larval abundance increased from 1977 to 2013 and was highest in the winter; most individuals were detected at nearshore stations. Over our time series, larval abundance corresponded closely to adult spawning stock biomass. Due to the lack of a direct relationship between our larval abundance estimates and a coastwide juvenile index, we examined several environmental factors (temperature, Chesapeake Bay discharge, Atlantic Multidecadal Oscillation [AMO], wind speed, and wind direction) for potential effects on the relative survival of larvae. Larval abundance had a significant negative effect on relative survival. Temperature and to a lesser extent wind speed and AMO appeared to exert the greatest effects on the early life survival of Atlantic Menhaden: cooler temperatures, intermediate wind speeds, and negative-phase AMO were the most favorable for survival. Our findings suggest that the observed reduction in recruitment is not a problem of larval supply but rather is limited by survival between the larval and juvenile stages. Received December 17, 2015; accepted May 31, 2016 Published online August 12, 2016
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 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".