Limited realized dispersal and introgressive hybridization influence genetic structure and conservation strategies for brown rockfish, Sebastes auriculatus

Abstract

Understanding patterns of connectivity among marine fish populations with demersal adults and pelagic larvae is critical for effective conservation of west coast rockfishes. The brown rockfish (Sebastes auriculatus) occurs in nearshore habitat and is common from northern Baja California, Mexico to northern California, rare off the outer coast of Oregon and Washington and again common in the inland waters of Puget Sound, Washington. Here we examine patterns of microsatellite DNA diversity from throughout the species' range as an indirect measure of long-term trends in larval dispersal. Genetic divergence was large and highly significant over all populations (F ST =0.056, P<0.0001), and was significantly correlated with geographic distance when considering coastal populations. The best estimates of mean coastal dispersal distance were on the order of 10 km or less per generation. Diversity was relatively low in the Puget Sound, suggesting that Puget Sound rockfish populations experienced a post-glacial founder effect followed by genetic isolation and low effective population size. Puget Sound individuals appeared to have recent mixed ancestry as a result of introgression with S. maliger and S. caurinus. Genetic isolation of Puget Sound fish provides a basis for consideration as a Distinct Population Segment (DPS) under the provisions of the Endangered Species Act. We recommend that coastal brown rockfish fisheries be managed at regional rather than coast-wide scales, and that design of marine reserve networks considers the surprisingly low realized dispersal distance of some species with high dispersal potential.

Conservation genetics of the franciscana dolphin in Northern Argentina: population structure, by-catch impacts, and management implications

“…Yet understanding population structure is a key component of management efforts (King and Burke 1999;Palumbi 2003;Waples 1998). In cases where there is absolute certainty about a species' population structure, specific protected areas could be set up to help conserve as much of the genetic diversity of the species as possible, or minimally for each identified population or distinct population segment (DPS) (Buonaccorsi et al 2005).…”

The utility and limitations of genetic data for stock identification and management of North Pacific rockfish (Sebastes spp.)

“…Because many rockfish species are closely related and occupy very similar habitats, hybridization and introgression may be important factors in the population dynamics and general genetic diversity for Sebastes, perhaps including speciation. A subsequent microsatellite study of brown rockfish came to similar conclusions regarding potential introgression (Buonaccorsi et al 2005). Seeb (1998) and Buonaccorsi et al (2005) hypothesize that introgression may occur more readily in areas with low abundance.…”

“…A subsequent microsatellite study of brown rockfish came to similar conclusions regarding potential introgression (Buonaccorsi et al 2005). Seeb (1998) and Buonaccorsi et al (2005) hypothesize that introgression may occur more readily in areas with low abundance. As rockfish populations drop, hybrid introgression may increase in frequency and geographic extent.…”

“…A successful network of MPAs must be optimized to the various dispersal distances of the species concerned. One of many potential beneficiaries of the application of genetic information to the formation of MPAs is brown rockfish (S. auriculatus), which occurs rarely in coastal Oregon and Washington, but is found in Puget Sound, Washington (as described above) (Buonaccorsi et al 2005). The numbers of individuals found in Puget Sound have dropped so low that a petition was filed in 1999 (though later denied) for their protection under the United States Endangered Species Act (Wright 1999).…”

Seasonal distribution of late larval and juvenile rockfish (Sebastes spp.) and associated environmental conditions off Oregon and Washington: new insights based on genetics

“…The dispersal of most larval fish seems to be highly diffusive and driven by ocean currents, although there is evidence that some rockfishes (particularly nearshore species) remain nearshore due to larval swimming behavior or limited water movement (Buonaccorsi et al, 2002(Buonaccorsi et al, , 2005Johansson et al, 2008). Environmental conditions also vary with ocean currents, and habitat variability can affect species abundance and diversity.…”