Genetic population structure of Pacific Hake, Merluccius productus, in the Pacific Northwest

Abstract

This study presents the first protein electrophoretic study of population structure within the Georgia Basin Pacific hake Distinct Population Segment, as defined under the U.S. Endangered Species Act. Forty-one allozyme loci (29 polymorphic) were analyzed in samples from three Pacific hake spawning populations on the west coast of North America: (1) Port Susan, Puget Sound, Washington (three temporal samples); (2) south central Strait of Georgia, British Columbia, Canada (two temporal samples); and (3) offshore of southern California (two temporal samples) (total n = 664). Mean heterozygosity over all loci was 12–13% for all populations. Within-population temporal samples were not significantly different from one another, but statistically significant differences were detected at 15 of the 29 polymorphic loci (p<0.05) among the three populations. Differences at eight of these loci were highly significant (p <0.001): ADA*, ALAT*, bGALA*, GPI-A*, sIDHP*, LDH-A*, MPI*, and PEP-B*. The two Georgia Basin populations were significantly different at six loci: bGALA*, sIDHP*, LDH–A*, MPI*, PGK*, and PGM–2* (p <0.05). Nei’s genetic distance (D) was 0.0006 between Port Susan and Strait of Georgia pooled temporal samples, and 0.005 between these populations and offshore Pacific hake. FST was 0.02 and 0.0046 among all three populations and among the Georgia Basin populations, respectively. Both FST estimates were significantly greater than zero, and the results suggest a high degree of demographic isolation among all three populations.Key wordsstock structuremarine fish geneticsallozyme electrophoresisgenetic differentiationdistinct population segmentPacific whitingheterozygosity