Research Document 2018/004

Assessment of softshell clam (Mya arenaria) of Québec’s coastal waters in 2016 – Methodology and Results

By Brulotte, S.

Abstract

The assessment of softshell clam (Mya arenaria) stocks of Québec’s coastal waters is conducted every three years. This document presents the data, methodologies, analysis and results that were presented during the peer review that took place in February 2017.

Softshell clams are found along most of Québec’s shoreline. This resource is commercially and recreationally harvested by using hand tools. Québec's coastal zone is divided into shellfish areas grouped into three major regions, the North Shore, Gaspé Peninsula-Lower St. Lawrence and Îles-de-la-Madeleine. Since 2006, landings from the Îles-de-la-Madeleine have been below 1.3 t and there has been no commercial harvesting in the Gaspé Peninsula and the Lower St. Lawrence. Landings reached a maximum of 1,173 t in 2000 on the Upper North Shore. They then declined to 190 t in 2009, a year prior to the closure of the processing plants. After a few years of low landing numbers, they rose somewhat in 2015 following the re-opening of a plant. Landings amounted to 72 t in 2015 and 83 t in 2016. Total allowable catches (TACs), introduced in 2015, were not met for the vast majority of areas. The measure of fishing effort in vendor-day and the catch per unit of effort (kg/vendor-day) is somewhat uncertain because there may have been more than one harvester per seller. In 2015 and 2016, the average size of clams landed was between 58 and 74 mm in the exploited areas. The proportion of clams of sub-legal size (< 51 mm) was generally below 5%. The survey conducted in 2014 on the Reserve Pessamit Sud bed suggests a stable density and biomass of legal-size clams compared to the 2010 survey. The results of the surveys conducted in 2016-2017 on Marie-Marthe Bank and Baie des Plongeurs beds show that the average density of legal-sized clams is 27 and 30 clams/m2 respectively. The closure of the Baie des Plongeurs from 2010 to 2015 appears to have favoured the recovery of this bed. In order to protect the reproductive potential of each shellfish area, it is recommended to collect less than 10% of the commercial biomass annually.

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