Research Document 2020/010

Stock assessment of Atlantic Surfclam, Spisula solidissima, of the Îles-de-la-Madeleine in 2018 – Methodology and Results

By Brulotte, S.

Abstract

The Québec Atlantic Surfclam fishery is confined to the Îles-de-la-Madeleine. The commercial fishery is carried out both by hydraulic clam dredges from vessels in coastal waters and by hand harvest in lagoons or near the shore by shore harvesters and divers. Hand harvesting is well established in the Îles-de-la-Madeleine in both the recreational and commercial fisheries. However, the extent of recreational harvesting is not well known.

Three beds were delineated in sub-areas 5A1 and 5B1 based on the location of the commercial dredge fishery. The CGE and East beds are in 5A1, and the North bed straddles sub areas 5A1 and 5B1. Since 2010, all fishing has been done on the North bed, whose known area is continually growing. Since 2012, the total allowable catch has been reached in 5A1 and 5B1. Fishing effort in 2018 was 21 and 23 days, respectively. Since 2012, the catch per unit effort (CPUE) calculated for the entire North bed has been above the 2004-2017 reference mean (223.0 kg per hour metre (kg/h·m)). Between 2009 and 2018, the exploitation rate index for the North bed ranged annually from 4.5% to 7.5%, with the average of the least three years being 6.4%. The size structures of clams landed in the last five years were fairly similar and the average size ranged from 132 to 137 mm.

Landings from the commercial hand harvest fishery vary with fishing effort. The averages for the last three years were 160 days and 42.3 t for divers and 113 days and 8.8 t for shore harvesters.

In one of the main areas harvested, A-12.1, the dive harvesting CPUE has been stable since 2016 and is at the 2005-2017 mean. The CPUE in A-09.5 has been fluctuating around its mean since 2014. Since 2008, the average size of landed clams has generally been around 131 mm in the sampled areas.

The shore harvesting CPUE varies from area to area. In A-09.5, it is rather stable and, in 2017 and 2018, it was near the 2005-2017 mean. The average size of landed clams is small compared with that of clams harvested by other methods. The average size in the last three years ranged from 111 to 120 mm, depending on the area.

Research Document 2020/010 (PDF, 2,699 KB)

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