Science Advisory Report 2016/023

Assessment of the Estuary and Northern Gulf of St. Lawrence (Areas 13 to 17, 12A, 12B, 12C and 16A) Snow Crab Stocks in 2015

Summary

• Stocks in the Middle and Lower North Shore of the Gulf of St. Lawrence (Areas 13, 14, 15, 16, 16A and 12C) had high commercial biomass. Only areas 16A and 12C showed signs of a decline in 2015. Fishery recruitment throughout these areas is still relatively high, but should decrease in the short (2016) or medium term (2017–2018). Conversely, the commercial biomass remains low in Area 17 despite a rise in 2015 caused by a recruitment that has started to recover. The commercial biomass in Areas 12A and 12B shows a decrease and recruitment during the next few years could depend on productivity in adjacent areas.
• The purpose of conservation is to maintain an adequate male reproductive biomass in order to ensure the recovery or maintenance of the population in a given area. Recommendations assume that the natural mortality rate will be the same in 2016 as in previous years.

Outlook

Area 17

• The rise in the combined index suggests a possible increase in catches in 2016 compared to 2015:
  1. An increase of 30% or more in catches would lead to a high harvesting intensity, which would slow the rate of expected increase in biomass available to the fishery and increase the risk of catching white crab;
  2. An increase of approximately 20% should lead to a moderate harvesting intensity and help increase the biomass available to the fishery;
  3. Any increase less than 15% could support an even more rapid increase in the biomass available to the fishery and reduce the risk of catching white crab.

Area 16

• The slight rise in the combined index suggests that it is possible to maintain or slightly increase catches in 2016 compared to 2015:
  1. An increase in catches greater than 10% would lead to a high harvesting intensity and could reduce the biomass available to the fishery in 2017;
  2. It is unlikely that a status quo or a maximum increase of 10% would lead to an excessively high harvesting intensity and would moderate the effects of lower expected recruitment in the medium term;
  3. Any decrease in catches could help maintain a substantial biomass available to the fishery over a longer period of time.

Area 15

• The combined index suggests that it is possible to slightly increase 2016 catches compared to 2015:
  1. An increase in catches greater than 10% could lead to a high harvesting intensity and would increase the expected biomass decline due to lower expected recruitment;
  2. It is unlikely that a 10% maximum increase would lead to an excessively high harvesting intensity and would moderate the effect of lower expected recruitment;
  3. A status quo or decrease in catches could help maintain a substantial biomass available to the fishery over a longer period of time.

Area 14

• The combined indicator declined slightly but remains very high, suggesting that catches in 2016 could be maintained at the 2015 level:
  1. An increase in catches could lead to a high harvesting intensity and would increase the effect of lower expected recruitment;
  2. It is unlikely that a status quo would lead to an excessively high harvesting intensity and would moderate the effect of lower expected recruitment;
  3. A decrease in catches could help maintain a substantial biomass available to the fishery over a longer period of time.

Area 13

• The rise in the combined index suggests that 2016 catches may be increased compared to 2015:
  1. An increase in catches greater than 20% could lead to a high harvesting intensity and would increase the effect of lower expected recruitment;
  2. It is unlikely that a 20% maximum increase would lead to an excessively high harvesting intensity and would moderate the effect of lower expected recruitment;
  3. A lower increase or a status quo could lead to the maintenance of a substantial biomass available to the fishery over a longer period of time.

Area 12A

• The drop in the combined index suggests that 2016 catches should decrease compared to 2015:
  1. A decrease of 20% or less in catches could lead to high harvesting intensity and a decrease in biomass available to the fishery in 2017;
  2. A decrease of approximately 30% should lead to a moderate harvesting intensity and help stabilize the biomass available to the fishery;
  3. An even greater decrease could help increase the biomass available to the fishery in the medium term.

Area 12B

• The uncertainty linked to the crab’s range during the post-season survey provides a rationale for increasing the weighting of the commercial biomass indicator during the fishery (CPUE). However, this indicator suggests that 2016 catches should decrease compared to 2015:
  1. A decrease in catches of 10% or less could lead to high harvesting intensity.
  2. A decrease of approximately 15% could lead to moderate harvesting intensity.
  3. A greater decrease could help stabilize the biomass available to the fishery.

Area 12C

• The drop in the combined index suggests that 2016 catches should decrease compared to 2015:
  1. A status quo in catches could lead to a high harvesting intensity and would increase the effect of lower expected recruitment;
  2. It is unlikely that a 10 to 15% decrease would lead to an excessively high harvesting intensity and would moderate the effect of lower expected recruitment;
  3. Any decrease greater than 15% could lead to the maintenance of a substantial biomass available to the fishery over a longer period of time.

Area 16A

• The uncertainty linked to the crab’s range during the post-season survey provides a rationale for increasing the weighting of the commercial biomass indicator during the fishery (CPUE). However, this indicator suggests that 2016 catches should decrease compared to 2015:
  1. A less than 15% decrease in catches could lead to a high harvesting intensity and would increase the effect of lower expected recruitment;
  2. It is unlikely that a 15 to 20% decrease would lead to an excessively high harvesting intensity and would moderate the effect of lower expected recruitment;
  3. Any greater decrease could help maintain a substantial biomass available to the fishery over a longer period of time.

This Science Advisory Report is from the February 16 and 17, 2016 meeting on the Assessment of the Estuary and northern Gulf of St. Lawrence Snow Crab stocks. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada Science Advisory Schedule as they become available.

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