Spatial synchronicity in recruitment of Atlantic cod (Gadus morhua) stocks off Newfoundland and Labrador and the Flemish Cap

Abstract

Spatial synchronicity in recruitment was examined for Atlantic cod (Gadus morhua) in the Newfoundland and southern Labrador (NL) and Flemish Cap regions. Recruitment was estimated using a cohort strength model for survey indices of abundance at pre-exploitation ages, and spatio-temporal covariation in recruitment was then examined. Patterns of recruitment synchrony were generally consistent with management boundaries. However, there were some exceptions that suggest structure at the sub-stock level and mixing across adjacent stock boundaries. In particular, we observed weak correlations between the eastern and western 3Ps RV (Research Survey) recruitment indices. We also observed strong correlations between the eastern 3Ps RV and the fall and spring 3NO RV recruitment indices, as well as fairly strong correlations between the southern 3L, central 3KL, and 3Ps sentinel GN and LT recruitment indices. Correlations between the summer 3M RV recruitment indices and all other survey recruitment indices included in our analysis were generally very weak, as was expected. We demonstrate that survey recruitment indices can be used to identify either areas of potential sub-stock structure or mixing or areas where recruitment drivers may be operating across or differentially within stock management boundaries. Hence, our results should improve the design of future stock structure research, and provide useful new information for fisheries management.