Benthic Habitats and the Effects of Fishing

Symposium Abstract: Effects of Fishing on the Benthic Habitat and Fauna of Seamounts on the Chatham Rise, New Zealand

M. R. Clark, A. A. Rowden, and S. O’Shea

doi: https://doi.org/10.47886/9781888569605.ch86

Major deepwater trawl fisheries occur for orange roughy on seamounts in New Zealand waters. These seamounts are often small, and trawling can be concentrated in a very localised area. Seamount habitat is thought to be productive, but also fragile, and there is growing concern from fisheries managers, environmental groups, and the fishing industry about effects of fishing on biodiversity and ecosystem productivity. This has prompted research to examine the nature and extent of deepwater trawling impact on seamount habitat in New Zealand. Results are presented from a recent survey where video and still imagery were applied to classify benthic habitat, and a new robust epibenthic sled used to sample the deepwater fauna. The study took place on the Chatham Rise where a group of 8 seamounts in close proximity allowed for a spatially unconfounded comparison of replicated fished and unfished seamounts. Commercial fisheries data were analyzed to determine the amount of trawling on each. Similarities within, and differences between, fished and unfished seamounts were identified for distribution of trawl gear modification of habitat; extent of live coral; macroinvertebrate assemblage composition, taxonomic distinctness and size spectra . This study provided information to help plan management strategies and develop effective management practices to allow both conservation and exploitation of seamounts, although more research is required. In May 2001, 19 seamounts throughout the New Zealand region, including several features on the Chatham Rise, were closed to bottom trawling as a precautionary measure.