Révision du stock du crabe commun (Cancer irroratus) jusqu'en 2023 dans le sud du golfe du Saint-Laurent (ZPH 23, 24, 25, 26A, 26B)

Abstract

Rock crab landings in the southern Gulf of St. Lawrence (sGSL) from the directed fishery remained stable around 4,500 t from 2000 to 2011 but have decreased steadily, reaching approximately 1,500 t in 2023. Current levels are at time-series lows. Concurrently, the annual number of fishing trips has been decreasing, from a maximum of 5,401 in 2001 to 1,660 in 2023. The proportion of rock crab licenses that are active has also declined, now at about 50% across all LFAs, with only 10% of active license holders reaching their personal allotments – an all-time low. The rock crab fishing effort is concentrated within the Northumberland Strait, with LFAs 25 and 26A accounting for an average of 74.8% of total directed landings in 2023. While bycatch sales have dropped to negligible levels, the extent to which rock crabs are used as bait by the lobster fishery remains unknown. A recent bycatch study found that male rock crabs are the most common non-target species caught in the lobster fishery. Standardized catch per unit effort (CPUEstd) indices for the primary LFAs rose initially, before stabilizing for a period (2003 – 2020), followed by a decline. This decline began earlier in LFA 26A (2015). A reduction in the size distribution of landed crabs within the fishing season can be an indication of fishery induced depletion. Size frequency distributions show no consistent trend of size reductions during the fishing season, except for LFA 26A which saw a small but significant decrease in size (less than 1%) on average over the course of a season. In locations where bio-collectors consistently catch rock crab, juvenile density has decreased, in some cases by more than 50% relative to levels a decade earlier. CPUEstd provides the most comprehensive index for setting an LRP. With relatively stable landings and CPUEstd between 2004 and 2011, the mean CPUEstd during this period (12.56 kg/trap) represents a proxy of CPUE at Maximum Sustainable Yield (CPUEMSY). In keeping with the recommendations of the Precautionary Approach, setting the LRP at 40% of MSY, or a proxy thereof, results in an LRP at a CPUEstd level of 5.02 (kg/trap). Current CPUEstd levels (7.38 kg/trap) are above this proposed LRP. Following the recommendations of the PA, 80% MSY would yield an USR of 10.05 (kg/trap) which would place this stock in the Cautious zone. Caution is warranted when using CPUE to identify stock status and any indications of hyperstability in the future should be carefully reviewed. Recognizing this caveat, data gaps, and latent fishing effort, the management of this stock should err on the cautious side.