Filling in a Data Gap of Area-Based Management: Fish Community Structure Across Landscape-Scale Habitat Patches

Fisheries managers are increasingly using area-based management approaches to match the scales at which subpopulations of fishes are distributed, data are collected, and fisheries are managed. These strategies require knowledge of local fish subpopulations and the habitats necessary to support them. Currently, we lack the necessary information about the distribution of fishes across a landscape (100s of meters to kilometers). Instead, most fish-habitat association studies have focused on fine-scale habitat types. We used data from visual strip-transects collected from the Delta submersible in 2004, 2007, and 2008 to characterize fish assemblages with respect to rocky bank habitat patches (defined as discrete areas of isolated hard substrate in similar depth zones, as determined from side-scan sonar images) near Point Lobos, California. Specifically, we examined the density, diversity, and length frequency of nearshore fish assemblages, with respect to three landscape-scale habitat characteristics: 1) proximity to the edge of rocky bank habitat patches, 2) patch shape, and 3) patch size. The density of all fishes did not vary significantly (p > 0.05) with respect to proximity to rocky bank habitat patch edge, with patch shape, or with patch size in the depth ranges investigated (30–100 m). However, species diversity positively correlated to proximity to rocky bank patch edges (p < 0.001), negatively correlated with patch shape (p = 0.012), and positively correlated with patch size (p < 0.001). The length frequency distribution of the fish community did not significantly differ with respect to proximity to the patch edge (p > 0.05), but did significantly vary with respect to patch shape (p < 0.001) and patch area (p < 0.001). These patterns were observed after accounting for the effect of depth and rugosity on the nearshore fish assemblage. Rocky bank habitat patch size explained more of the variability in the fish community structure than the patch shape or proximity to the patch edge. These results demonstrate that predictable patterns occur in the nearshore fish assemblage with respect to landscape-scale habitat characteristics in central California. This increased understanding of the response of the nearshore fish assemblages to landscape-scale habitat characteristics will enable managers to develop more effective area-based management strategies, improving fisheries management locally as well as regionally.