Nearshore marine communities at three New Zealand sub-Antarctic islands

The sub-Antarctic islands of New Zealand are biodiversity hotspots in the Southern Ocean, containing numerous endemic species and providing breeding grounds for seabirds and marine mammals. However, due to their remoteness and harsh environments, many of their marine ecosystems are relatively unexplored and potentially at risk from alien invasive species. To better understand nearshore marine ecosystems at three New Zealand sub-Antarctic islands (Snares Islands, Auckland Islands and Campbell Island), we sampled nektobenthic fish and mobile macroinvertebrates at 40 sites (15–20 m depth) using baited remote underwater videos (BRUVs). MaxN of each species in the videos was recorded in 5-min intervals for 45 min, allowing analyses of MaxN over the whole deployment, as well as change through time during the deployment. Species distributions appeared to reflect both the geomorphological and biogeographic traits of the islands. The Auckland Islands and Campbell Island contain large inlets dominated by mobile crustaceans, and biological trends followed gradients in marine exposure along inlets. In contrast, the Snares Islands are mostly exposed coast and contained a higher diversity of fish species common with mainland New Zealand. We suggest that differences in nearshore marine communities between these islands are likely due to the combined effects of habitat availability, biogeography, and ocean temperature.