Juvenile Chum (Onchorhynchus keta) and Pink Salmon (O. gorbuscha) use of submerged vegetative habitats in Southeast Alaska

Enclosed data and code are an archive for the manuscript submitted to Marine and Coastal Fisheries "Juvenile Chum (Onchorhynchus keta) and Pink Salmon (O. gorbuscha) use of submerged vegetative habitats in Southeast Alaska". We include two scripts, one for each objective in the manuscript and the corresponding required datasets to run those analyses and generate figures and tables for the manuscript. Manuscript abstract Apex predator-initiated trophic cascades occur in many nearshore marine habitats including eelgrass meadows and kelp forests that simultaneously serve as critical habitat and a food source for commercially and ecologically important fish species, including juvenile salmon (Oncorhynchus spp.). Yet the potential relationships among apex predators such as sea otters (Enhydra lutris), submerged vegetated habitats, and juvenile salmon are not well understood. We investigated (1) juvenile salmon abundance in eelgrass meadows and understory kelp beds in Southeast Alaska using data from historical NOAA surveys (sampled 1998- 2007) and (2) potential drivers of juvenile Chum (Oncorhynchus keta) and Pink Salmon (O. gorbuscha) abundance in Southeast Alaska eelgrass meadows, including seasonality, sea otter density, eelgrass biomass, and distance from anadromous stream outlets. We found greater abundance of juvenile Chum Salmon in understory kelp compared to eelgrass, whereas Pink Salmon abundance did not differ between habitats. Seasonality and sea otter density were most important for explaining Chum Salmon abundance in eelgrass meadows, whereas Pink Salmon abundance showed strong seasonality and was positively associated with sea otter density, distance from anadromous stream, and negatively associated with eelgrass biomass. Growth and survival while juvenile salmon are out-migrating from streams and relying on nearshore vegetated habitats can determine if salmon recruit to fisheries as adults; thus, understanding driving forces, like apex predators, vegetated habitats, and their structuring roles in the nearshore is critical for informing adaptive coastal and fisheries management.