Seamount benthic macrofauna off southern Tasmania: community structure and impacts of trawling

Abstract

The benthic macrofauna of a group of small seamounts south of Tasmania was surveyed with a dredge and camera to assess the impact of trawling for orange roughy (Hoplostethus atlanti- cus; Trachichthyidae) and the efficacy of a proposed marine reserve. The seamounts were generally 300 to 600 m high and the peaks ranged from 660 to 1700 m depth. The fauna was diverse: 262 spe- cies of invertebrates and 37 species of fishes were enumerated, compared with 598 species of inver- tebrates previously reported from seamounts worldwide. On seamounts that peaked at depths 1400 m. These seamounts were dominated by sea urchins and had lower biomass and fewer species per sample. However, few species were restricted to either the shallowest or deep- est depths sampled. The fauna unique to the region's seamounts appears to be adequately repre- sented within a recently established 'Marine Protected Area' that encloses 12 seamounts that peak at depths >1150 m.