Benthic invertebrate bycatch from a deep-water trawl fishery, Chatham Rise, New Zealand

Abstract

1. Benthic invertebrate bycatch was collected during trawling for orange roughy (Hoplostethus atlanticus) at water depths of 662–1524 m on the northern and eastern Chatham Rise, New Zealand, in July 1994. Seventy-three trawl tows were examined, 49 from ‘flat’ areas and 24 from two groups of ‘hills’ (small seamounts). Benthos was recorded from 82% of all tows. 2. Some 96 benthic species were recorded including Ophiuroidea (12 spp.), Natantia (11 spp.), Asteroidea (11 spp.), Gorgonacea (11 spp.), Holothuroidea (7 spp.), and Porifera (6 spp.). 3. Cluster analysis showed the bycatch from flats and hills to differ significantly. Dominant taxa from flats were Holothuroidea, Asteroidea and Natantia; whereas taxa most commonly recorded from hills were Gorgonacea and Scleractinia. Bycatch from the two geographically separate groups of hills also differed significantly. 4. The largest bycatch volumes comprised corals from hills: Scleractinia (Goniocorella dumosa), Stylasteridae (Errina chathamensis) and Antipatharia (?Bathyplates platycaulus). Such large sessile epifauna may significantly increase the complexity of benthic habitat and trawling damage may thereby depress local biodiversity. Coral patches may require >100 yr to recover. 5. Other environmental effects of deep-water trawling are briefly reviewed. 6. There is an urgent need to assess more fully the impact of trawling on seamount biotas and, in consequence, possible conservation measures. © 1997 John Wiley & Sons, Ltd.