Structure of nearshore fish assemblages in relation to varying levels of habitat complexity

Abstract

Complex kelp and rocky habitats can be beneficial to fishes, however, their use of these habitats is poorly understood in northern latitudes. This study examined nearshore kelp habitats to examine the potential effects of kelp density and substrate topography on nearshore fish communities in Kachemak Bay, Alaska. Fish were collected from multiple sand, understory kelp, and understory and canopy kelp sites, along with kelp and substrate complexity measurements. Standard Monitoring Units for the Recruitment of Fish (SMURFs), light traps, shrimp pots, and SCUBA visual surveys were all employed in these collections. Relative fish abundance and community composition varied temporally in all habitats. The dominant fish families were gadids, pleuronectids, hexagrammids, and sebastids. Habitat use differed significantly temporally and spatially in relation to size class. These differences were family specific. Community analysis of the dominant fish families showed that different habitat complexities supported distinct fish assemblages. Low complexity sand habitats were particularly important for juvenile pleuronectids in this region and complex nearshore kelp habitats may be essential fish habitat for juvenile Pacific cod. Although these high complexity nearshore environments may be challenging to sample, they support large fish assemblages and may be essential to a variety of fish families and species.