Reproductive ecology of the soft-shell clam (Mya arenaria) in Eastern New Brunswick, Canada: Assessing size-at-maturity and spawning time to inform fisheries management

Abstract

Soft-shell clams, Mya arenaria, are fished commercially and recreationally across much of their distribution. Several management measures have been implemented in Atlantic Canada to regulate the clam fishery, including a minimum legal size limit of 50 mm. This legal size limit, however, is not based on contemporary data. A regional understanding of soft-shell clam reproductive biology in eastern New Brunswick is lacking, yet the management of this fishery would greatly benefit from this localized knowledge. As such, we collected soft-shell clams in Kouchibouguac National Park, New Brunswick, Canada, during the Spring, Summer and Fall of 2021, to assess size-at-maturity and time of spawning. Histology was used to determine the sex and maturity stage of individual soft-shell clams and maturity ogives were generated for female and male clams. Temporal changes in the gonadosomatic index (GSI) were also used to identify likely spawning times for female and male clams. Sex ratios were significantly unbalanced for most of the sites sampled, favouring females, with an overall sex ratio of 2.3:1 (F: M). Size-at-maturity was estimated at 39.7 mm and 40.7 mm for female and male soft-shell clams, respectively. Overall, GSI was higher in males, peaking in late May, declining sharply in June, and showing a more gradual decline from July until September. Female GSI also peaked in late May, but exhibited a continuous, gradual decline from mid-June through to September, suggesting that peak spawning likely occurred from late May to mid-June in 2021 but that some degree of spawning likely continued thereafter. Overall, these results provide insights into the reproductive biology of sub-legal sized soft-shell clams in eastern New Brunswick, providing managers with contemporary scientific information.