Evaluation of Methods for Separation of Gulf of St. Lawrence Beaked Redfishes,Sebastes fasciatusandS.mentella: Malate Dehydrogenase Mobility Patterns Compared with Extrinsic Gasbladder Muscle Passages and Anal Fin Ray Counts

Abstract

Malate dehydrogenase (MDH) electrophoretic mobility patterns were used as a standard against which field methods involving anal fin ray counts (AFCs) and extrinsic gasbladder muscle (EGM) rib passage patterns were compared to separate the beaked redfish species, Sebastes fasciatus and S. mentella. The frequencies of MDH-A phenotypes were determined for 1125 beaked redfish examined from a winter survey in 1983 and 376 from a summer survey in 1984. Allele frequencies were calculated from the MDH-A phenotypic data for the winter survey. The low mobility of the A2phenotype was characteristic of 90% of S. fasciatus sampled at depths < 320 m in winter and at depths < 250 m in summer. The high-mobility A1and heterozygotic A1/A2phenotypes were prevalent in 95% of S. mentella sampled below these depths. The mobility patterns agreed with predominant AFCs ([Formula: see text] for S. fasciatu[Formula: see text] for S. mentella) for all stations in the deep and shallow zones. The MDH mobility patterns showed 93% agreement with EGM patterns for S. fasciatus but only 53% agreement for S. mentella. An overlap of AFCs, of main EGM patterns, and of tendon to vertebrae attachments and the variation from set to set in A1/A2heterozygotic phenotypes suggest that these species hybridize in the Gulf of St. Lawrence.