Turnover time and annual migration of Clupea harengus Atlantic herring on the German Bank and Scot's Bay spawning grounds :

Abstract

This study examined eleven years of mark and recapture data to quantify turnover time, defined as the time required for individuals to aggregate, spawn and exit the spawning area, of Clupea harengus Atlantic herring on the German Bank and Scot's Bay spawning grounds off eastern Canada. Herring migrating from the Scot's Bay spawning ground have a shorter mean turnover time and faster dispersal rate than German Bank herring. Most post-spawned Scot's Bay herring migrated to the approaches of the Bay of Fundy where they mixed with German Bank herring. German Bank herring were more broadly distributed, occurring near the approaches of the Bay of Fundy, throughout the Gulf of Maine, and on Scotian Shelf. No mixing of the two populations occurred during spawning indicating self-sustaining reproductively isolated populations. The two populations only mixed during feeding and overwintering. Population specific turnover times calculated in this study improve current methods of estimating spawning stock biomass, thereby reducing the risk of overexploiting the resource.