MIXED-STOCK ANALYSIS OF ATLANTIC COAST STRIPED BASS (MORONE-SAXATILIS) USING NUCLEAR-DNA AND MITOCHONDRIAL-DNA MARKERS

Striped bass (Morone saxatilis) stocks comingle along the northeastern United States and Canadian coasts and support mixed-stock fisheries i n which stock compositions fluctuate widely. Many approaches to stock analysis of these populations have been tried. The recent use of mitoc hondrial DNA (mtDNA) haplotype frequency data showed promising results , despite low levels of mtDNA variation; to improve resolution, we use d a single-copy nuclear DNA (nDNA) probe with mio mtDNA markers (major length variants and Tag I variants), alone or in combination. Striped bass reference collections were from the Hudson River and Chesapeake Bay, and mixed-stock collections (1989 and 1991) were from eastern Lon g Island, New York. The combination of the nDNA and mtDNA major length variant data provided lower but still quite high resolution potential (D-st = 0.417) in mixed-stock analysis (1991 collection) than the com bination of all three markers (D-st = 0.552). However, unlike the Huds on River stock, the Chesapeake Bay stock is composed of multiple subst ocks that vary significantly in the frequencies of Taq I variants; thi s among-substock variation destabilizes the Chesapeake Bay reference d ata set and the resultant mixed-stock estimates. Thus, we recommend an approach based on composite nDNA and mtDNA major length variant marke rs.