Coastal and lowland fish assemblages of New Britain: a mix of habitat and setting specialists and generalists

Context We lack basic scientific knowledge of coastal fish faunal diversity and distribution in the islands of the Bismarck Sea, such as New Britain. High-flow rivers and microtidal conditions result in a patchwork of salinity regimes, which creates a diversity of unique environmental settings and habitat features, such as extensive, low-salinity Nypa fruticans mangrove-palm swamps adjoining major rivers. Aims Focusing on coastal, estuarine and lowland freshwater systems, we investigated the environmental settings present, the habitat features they contain and the patterns of utilisation by different fish species, to better understand the potential for adverse impacts from human activities. Methods We used remote underwater video to define fish assemblages and habitat associations. Key results Fish assemblages contained a unique mix of species with diverse habitat and physical requirements. Conclusions A large proportion of New Britain’s coastal and lowland fish use multiple environmental settings, underlining the importance of hydrological connectivity in enabling day-to-day and life-history migration requirements of the fish community. Implications The complex inter-setting utilisation of New Britain coastal and lowland fishes, their reliance on unique habitats (some derived from local and upstream forests), and intact watersheds, places them at risk from the landscape impacts stemming from extensive logging and oil palm.