Annulus Formation and Growth of Atlantic Surfclam (Spisula solidissima) Along a Latitudinal Gradient in the Western North Atlantic Ocean

Abstract

ABSTRACT Age data play an important role in the Atlantic surfclam [Spisula solidissima (Dillwyn, 1817)] stock assessment and their accuracy depends on understanding the periodicity and timing of annulus formation. In the United States, the surfclam stock area spans approximately 5° latitude in the northwest Atlantic. In recent years, surfclams at the southern end of this area have undergone changes in abundance, distribution, and growth, all likely due to increasing ocean temperature. To determine whether the periodicity or timing of annulus formation has also changed, shells from live surfclams were collected during every month of the year from three regions spanning 4° latitude: southern New England (northernmost), New Jersey (middle), and the Delmarva Peninsula (southernmost). Edge analysis and marginal increment analysis indicated a single annulus was formed each year in each region and by all age groups, verifying surfclams can still be aged reliably throughout the managed area. Some regional or ages...