A Survey Of Fish Assemblages In Eelgrass And Kelp Habitats Of Southeastern Alaska

Essential Fish Habitat

One of the most important changes in the 1996 reauthorization of the Magnuson-Stevens Fishery Conservation and Management Act was a requirement to identify and describe essential fish habitat (EFH) for species included in federal fishery management plans (FMPs) (National Marine Fisheries Service 1999). The amended act gave heightened importance to fish habitat in resource management decisions. Essential fish habitat is defined as those waters and substrate necessary for spawning, breeding, feeding, or growth to maturity (North Pacific Fishery Management Council 1998). Identifying EFH requires basic information on fish distribution and habitat use. Such information is lacking, however, for many FMP species in Alaska, especially for early life stages.

Summary

For most federally managed fish species in Alaska, basic information on distribution and use of nearshore marine habitats is lacking, especially for early life stages. To gain a better understanding on the use and importance of nearshore habitats as essential fish habitat (EFH), we compared fish assemblages between two distinct habitat types (eelgrass, Zostera marina, and kelp, mostly Laminaria saccharina) at 30 sites in southeastern Alaska from 1998 to 2000. Sites were selected in four regions to cover a geographical gradient from north to south and from inside to outside waters. Fish were collected by beach seine from June through August each year. A total of 102 seine hauls yielded more than 51,000 fish comprising 54 species; 23 of the species that we captured are included in a salmon or groundfish fishery management plan in Alaska.

Species richness was greater in eelgrass than in kelp, whereas the Shannon-Wiener diversity index (HN) was similar between habitat types. Abundance of fish varied considerably between habitat types and among regions, often because of the patchy distribution of some species. Distribution patterns were evident for some species by differences in catch among regions.

Eelgrass and kelp support high biodiversity and are important habitats for juveniles of many commercially important or forage fish species. Knowledge of fish assemblages and their use of intertidal and shallow, subtidal vegetation will help managers identify EFH. Once identified, managers can then make recommendations to protect or minimize impacts to EFH from human disturbance.