Stock delineation of dover sole in the california–british columbia region, based on tagging studies conducted during 1948–1979

During 1948–1979, 34,377 Dover sole Microstomus pacificus were tagged and released in the California–British Columbia region, and 4,275 (12.4%) were subsequently recovered. A coastwide, interagency investigation began in 1985 to analyze the results of these studies with respect to stock delineation. Results of the tagging studies, and of other studies involving age determination, established that the Dover sole is a long-lived species. Maximum time at liberty for recoveries ranged from 13 to 22 years among studies, although 89–97% of the recoveries came within the first 5 years after tagging. Age-determination studies suggested a maximum age in the range of 36–52 years. Thus, there was adequate time for the tagged fish to disperse from their respective tagging areas. Few tagged Dover sole were recovered in international statistical areas north or south of their tagging area. Recoveries indicated that the fish occupied shallow water (<200 m) during spring-summer and deep water (>199 m) during autumn–winter. Evidently, adult (and probably juvenile) Dover sole form individual “stocks” with minimal intermingling. In contrast, the larvae likely intermingle extensively, since other studies have revealed a long pelagic existence far offshore, Resulting complexities for stock assessment are discussed, together with suggestions for further studies dealing with stock delineation.