Scotian Shelf Snow Crab Assessment
Bibliographic record
Abstract
Fishing effort in 2022 was 8,600 trap hauls in north-eastern Nova Scotia (N-ENS), 56,500 trap hauls in south-eastern Nova Scotia (S-ENS), and 2,000 trap hauls in 4X. This represents a change of -2.3%, -30.1% and -35.5%, respectively, relative to the previous year. Landings in 2022 were 977 t in N-ENS; 7,323 t in S-ENS; and 35 t in CFA 4X (season ongoing), representing a change of 8.4%, -12.1%, and -68.2%, respectively, relative to 2021. Total allowable catches (TACs) for 2022 were 979 t, 7,345 t, and 125 t in N-ENS, S-ENS, and 4X, respectively. Non-standardized fishery catch rates in 2022 were 113 kg/trap haul in N-ENS, 130 kg/trap haul in S-ENS, and 17 kg/trap haul in 4X. This represents a change of 10.8% in N-ENS, 26.2% in S-ENS, and -52.8% in 4X (season ongoing) relative to the previous year. Though the spatial extent of exploitation was smaller, many of the exploited areas showed elevated catch rates. The percentage of soft-shelled crab in commercial catches in the 2022 season was 6.4% in S-ENS and 0% in N-ENS; there was no sampling to-date in 4X (season on-going) for the 2022–2023 season. In 2021, the percentage of soft-shelled crab in commercial catches in S-ENS was 11.2% (low sampling intensity); there was no sampling in N-ENS and 4X. In 2022, numbers of Snow Crab with carapace condition 5, derived from At-Sea Observer sampling data, were higher in N-ENS and S-ENS than historical trends; however, as At-Sea Observer sampling targets were not met, there is uncertainty in the representativity of the data when comparing to historical trends. Bycatch of non-target species is low (<< 1% of total catch) in all Snow Crab fishing areas; however, as sampling targets for At-Sea Observer coverage have not been met in recent years, there is uncertainty in the representativity of the data. Egg and larval production is expected to be high in the next year in all areas except N-ENS. Average bottom temperatures observed in the 2022 Snow Crab survey were near or above historical highs in all areas. Average viable habitat surface area has declined to historical lows in 2022. Based on stomach sampling, Atlantic Halibut, Atlantic Wolffish, Thorny Skate, and other skate species appear to be the predominant predators of Snow Crab on the Scotian Shelf. Overall, higher predation mortality seems likely in N-ENS and S-ENS and lower in 4X. Densities of co-occurring species such as shrimp have declined, possibly due to large-scale environmental change. In N-ENS, the modelled biomass (pre-fishery) of Snow Crab in 2022 was 3.69 kt, relative to 3.96 kt in 2021. In 2022 there was a high possibility of mobility of crab and elevated predation in N-ENS. In S-ENS, the modelled biomass (pre-fishery) was 41.93 kt, relative to 44.83 kt in 2021. In 4X, the 2022–2023 season’s modelled biomass (pre-fishery) was 0.78 kt, relative to 0.89 kt in the 2021–2022 season. In 2022, 83 of 385 survey stations were not completed (all missing stations were in S-ENS). In N-ENS, though recruitment continues at low levels, a gap in future recruitment to the fishery is expected for the next one to three years in N-ENS. Following the Precautionary Approach based reference points for the area, N-ENS is in the healthy zone. However, a more conservative harvest strategy may support the stock in bridging the expected gap in recruitment. In S-ENS, recruitment to the fishery is likely to continue at a moderate rate for the 2023 season. The S-ENS stock remains in the healthy zone. Exploitation rates derived from the fishery model have been declining in recent years. Continuation of the current harvest strategy would support maintenance of stock status of S-ENS in the healthy zone. In 4X, low to moderate levels of recruitment are expected for the next two years. The area is also in the southern-most extent of Snow Crab distribution in the North Atlantic and viable habitat has been depressed for many years. Following the Precautionary Approach based reference points for the area, 4X is in the cautious zone. A more conservative harvest strategy is advised.
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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 | 0.000 | 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) | 0.004 | 0.001 |
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".