Research Document - 2016/074

Stock assessment of Atlantic Surfclam, Spisula solidissima, of the Îles-de-la-Madeleine, Québec in 2015 – methodology and results

By Sylvie Brulotte

Abstract

In Québec, the Atlantic Surfclam fishery is conducted exclusively in the Îles-de-la-Madeleine. Boats harvest the clams with a hydraulic dredge in coastal waters. Divers and shore harvesters also use hand tools to gather them in lagoons or near shore. Hand tools are used in both recreational and commercial fisheries.

Three beds were delineated in 5A1 and 5B1 sub-areas based on logbook harvesting positions from dredge fishery. The CGE and East beds are located in 5A1 and the North bed straddles sub-areas 5A1 and 5B1. Since 2009, all harvesting has been focused on the North bed, whose known area continues to grow. Since 2012, the total allowable catch (TAC) has been caught in 5A1 and 5B1. In 2015, 126 t were landed with a fishing effort of 26 days in 5A1 and 115 t were landed with a fishing effort of 19 days in 5B1. Catches per unit effort (CPUE) calculated for the entire North bed have been high and stable since 2009. Since 2009, between 5.6% and 9.3% of the North bed area has been dredged annually, and the yearly average for the last three years was 7.5%. Good yields and size structure stability in recent years are attributable to the constant movement of fishing effort to new areas of the North bed.

Commercial hand harvesting information by divers and shore harvesters are most likely incomplete, and the extent of recreational hand digging is unknown. This hand digging fishery, mainly the recreational fishery is very popular and well-developed. Known commercial hand digging landings vary with fishing effort. The averages for the last three years are 35 t and 231 days. Since 2010, CPUEs for commercial harvesting by divers and shore harvesters have been fairly stable, but both are generally below the reference average. Since 2008, the annual average size of clams collected by diving is near the reference average. Clams gathered by shore harvesters are smaller and their average size is smaller than that of clams harvested by other methods. However, clam size has risen since the minimum legal size was increased in 2014.

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