The purpose of this study was to examine the genetic stock structure of herring within Prince William Sound (PWS) and the connections to herring stocks outside of PWS. Fisheries managers needed to understand herring stock genetics in order to set management objectives that could aid herring recovery in PWS. One of the key objectives of this study was to use the genetic makeup of herring populations to determine if one or multiple stocks exist in PWS. For example, are the fish that spawn on Montague different than those that spawn in Port Gravina or are they different portions of one large population?
Researchers from NOAA coordinated with the Alaska Department of Fish and Game (ADF&G) and other researchers around the state to collect herring samples from different spawning locations in PWS and its adjacent regions. Herring were collected from eastern and western PWS, SE Alaska, Yakutat and Kayak Island, Cook Inlet, Shelikof Strait, and Kodiak Island. Genetic information was obtained from thirteen genetic markers. These markers were (genes or DNA-sequences that identify the relatedness of individuals) were used to identify the genetic identity of each herring sample, which then was evaluated to determine how related the various spawning populations were.
Analyses of the herring in eastern PWS showed that the genetic markers were the same among bays, between year classes, and over years. Collections from Montague Island and Evans Island (western PWS) indicated a weak signal of differentiation from eastern PWS collections. However, the genetic differences found were not significant enough to suggest that there are two separate stocks in PWS. PWS herring were found to be genetically similar to herring east of PWS (Kayak Island and Yakutat), but are significantly different than herring west of PWS (Kodiak, Cook Inlet, and Shelikof Strait). Examining the genetics of individual fish in Cook Inlet shows that they are a mix of fish with PWS and Shelikof Strait genetics. These findings suggest that gene mixing is occurring between PWS herring and stocks east of PWS, either continuously or intermittently.