The Distribution of Nearshore Fishes in Kelp and Eelgrass Communities in Prince William Sound, Alaska: Associations with Vegetation and Physical Habitat Characteristics

Abstract

The nearshore (less than 20 m depth) demersal fish community in Prince William Sound, Alaska, is dominated by Pacific cod, Gadus macrocephalus, pricklebacks (mostly Arctic shanny Stichaeus punctatus), gunnels (mostly crescent gunnels Pholis laeta), a variety of greenlings (Hexagrammidae) and sculpins (Cottidae). During summer, the spatial distribution of fishes, over scales of 100's of m to 10's of km, varied by habitats characterized by different vegetation types. Juvenile Pacific cod and greenlings were numerically dominant in eelgrass, Zostera marina, beds. Pricklebacks and sculpins were dominant in areas with an understory of the kelps Agarum cribrosum and Laminaria saccharina. Greenlings and sculpins were the most abundant demersal fishes in more exposed sites with a canopy of Nereocystis luetkeana and an understory of L. bongardiana. Measured habitat variables, including vegetation type, slope, vegetation biomass, and substratum type, explained a significant proportion of the variation in the presence or absence of most fishes. The relative importance of different habitat characteristics varied between taxonomic groups of fishes. Vegetation type explained a significant proportion of variation for cod, rockfishes, and ronquils. Juvenile cod were closely associated with eelgrass, while rockfish and ronquils were associated with kelps. Pricklebacks and rockfishes were more frequently observed on steeply sloped shorelines, while ronquils were more often found at sites with higher biomass of vegetation. Within A. cribrosum habitats, more greenlings and sculpins were present at sites where algal biomass was higher. Also, sculpins were more abundant in deeper water and gunnels were more abundant in shallow water within this habitat. These associations may not have been causative. However, evidence suggests that some differences between fish communities in eelgrass and Agarum beds may have been causally related to vegetation characteristics. The possible roles of different vegetation types as refugia from predators or as sources of prey are discussed.