Science Advisory Report 2020/032

Assessment of Softshell Clam Stocks in Québec Coastal Waters

Summary

• Softshell clams are exploited by commercial and recreational harvesters. There is no commercial fishery in the Gaspé Peninsula and the Lower St. Lawrence. Landings from the Îles-de-la-Madeleine are low (< 3 t) and little information is available to assess the status of the resource. There is no recommendation for this region.
• Landings reached a maximum of 1,173 t in 2000 on the Upper North Shore but averaged only 26 t over the last three years (2017-2019). Total allowable catches (TACs) were not met due to the low effort deployed. Since 2010, commercial landings have come mainly from ten shellfish areas.
• Since 2017, the average size of clams landed has been between 65 and 74 mm in the six sectors sampled on the Upper North Shore. The proportion of sublegal size clams (<  51 mm) in the landings is very low.
• Twenty-three shellfish areas on the Upper North Shore were surveyed from 2016 to 2019. Eight of these sectors had already been surveyed from 2002 to 2014. The commercial density increased significantly in five of these eight sectors. However, the area currently covered by a few beds is much smaller than that measured during surveys conducted from 1967 to 1977.
• The biomass of legal-size clams was calculated for each of the areas surveyed. In order to protect the reproductive potential of each shellfish area, it is suggested that the exploitation rate be limited to a maximum of 5% of the commercial biomass.
• Some sectors may be more vulnerable to a 5% exploitation rate. It is therefore suggested that this rate be adjusted downwards for these sectors. Thus, the rate should be minimal for sectors with a harvestable area of less than 0.05 km² and about 2.5% for sectors where the density of 20-50 mm softshell clams is less than 15 clams/m².
• Suggested exploitation rates apply to all harvesting (commercial and recreational). The impact of recreational harvesting, an activity valued by coastal communities, remains unknown. It would be important to quantify the effort and harvesting of this activity, which is also a source of mortality among juveniles.

This Science Advisory Report is from the meeting of February 25, 2020, on the Assessment of Quebec inshore waters Softshell clam. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada Science Advisory Schedule as they become available.

Science Advisory Report 2020/032 (PDF, 1,286 KB)

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