High-resolution, habitat-suitability maps for the conservation and management of vulnerable marine ecosystems on the Louisville Seamount Chain, south Pacific Ocean

Abstract

Vulnerable marine ecosystems (VMEs) are ecosystems at risk from the effects of fishing activity or other kinds of disturbance, as determined by the vulnerability of their components (e.g., habitats, communities or species). Habitat suitability modelling is being used increasingly to predict distribution patterns of VME indicator taxa in the deep sea (where data are particularly sparse), and the models are considered useful for marine ecosystem management. The Louisville Seamount Chain is located within the South Pacific Regional Fishery Management Organisation (SPRFMO) Convention Area, and some seamounts are the subject of bottom trawling for orange roughy by the New Zealand fishery. The aim of the present study was to produce high-resolution, habitat suitability maps for VME indicator taxa and VME habitat on these seamounts, in order to aid the design of within-seamount spatial closures to protect VMEs. We used a multi-model habitat suitability mapping approach, based on bathymetric and backscatter data collected by multibeam echo sounder survey, and data for the stony coral and habitat-forming VME indicator species Solenosmilia variablis collected by towed underwater camera. Maps resulting from our models showed that suitable habitat for this species is distributed around the summit-slope break of seamounts, and along ridges that extend down the seamount flanks. Only the flat, soft sediment summits are predicted to be unsuitable habitat for this stony coral species. We translated a definition for stony coral-reef habitat into a Solenosmilia variablis abundance-based threshold in order to use our models to map this VME habitat. These maps showed that coral-reef occurred in small and isolated patches, with most of the seamounts predicted to be unsuitable habitat for this VME. We discuss the implications of these results for spatial management closures on the Louisville Seamount Chain seamounts and the wider SPRFMO area, and future modelling improvements that could aid efforts to use habitat suitability maps for managing the impact of fishing on vulnerable marine ecosystems.