Epidemiology of bitter crab disease (Hematodinium sp.) in snow crabs Chionoecetes opilio from Newfoundland, Canada
Bibliographic record
Abstract
The parasitic dinoflagellate Hematodinium sp. causes a condition known as bitter crab disease (BCD) in snow crabs Chionoecetes opilio and Tanner crabs C. bairdi. As the name of the condition implies, crabs infected with BCD are unmarketable due to their bitter flavor. We surveyed the distribution of BCD in 3 regions within the snow crab fishery of Newfoundland from 1997 to 2003. Over time, the disease has become firmly established in Conception and Bonavista Bays and persists at low levels on the Avalon fishing grounds. An epizootic occurred within Bonavista and Conception Bays in 1999 and persisted in Conception Bay in 2000, reaching prevalences of over 2% to 9% in trapped and trawled male crabs and from 19 to 26% in trawled and trapped female crabs, respectively. Infections were highest in females and small males, i.e. the unfished and pre-recruit portions of the fishery. In a mortality study, all of the naturally infected crabs died and 50% of the experimentally inoculated crabs died. Patterns in the molting cycle and prevalence of infection indicate that transmission occurs during the post-molt condition, and that overt infections probably develop 2 to 4 mo later with mortalities occurring at least 3 to 4 mo thereafter. The hydrography of this bay may have contributed to the epizootic as infections were centered within the deeper confines of the bay. Analysis of various abiotic factors uncovered a significant positive association between prevalence, depth and mud/sand substrates; the nature of this relationship was not apparent but may be related to diet or alternate hosts. Lastly, given the increase in BCD in snow crabs in Newfoundland, we recommend that fishery management programs for Chionoecetes fisheries employ non-selective gear to monitor for Hematodinium infections in female and juvenile crabs because these under-sampled members of the population may forewarn of impending recruitment declines that might otherwise remain unexplained.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.007 | 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 teacher head, 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".