Individual study: Impacts of bottom trawling on deep-coral ecosystems of seamounts are long-lasting
Althaus F., Williams A., Schlacher T., Kloser R., Green M., Barker B., Bax N., Brodie P. & Hoenlinger-Schlacher M. (2009) Impacts of bottom trawling on deep-coral ecosystems of seamounts are long-lasting. Marine Ecology Progress Series, 397, 279-294
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Designate a Marine Protected Area and prohibit bottom trawling
A replicated, site comparison study in 2006 of 25 deep-sea seamounts located south of Tasmania, South Pacific Ocean, Australia (Althaus et al. 2009) found that, four to nine years after prohibiting bottom trawling in marine protected areas, invertebrate community composition was different and abundance lower at protected seamounts compared to trawled and natural (never trawled) seamounts, and diversity and species richness was similar to trawled but lower than at natural seamounts. Community data were reported as graphical analyses and diversity data as diversity indices. Species richness was similar at protected (46 species/1,270 m2) and trawled seamounts (46), but lower than natural seamounts (52). Abundance was lowest at protected (1–3 individuals/m2), compared to trawled seamounts (3–5), and natural seamounts where abundance was the highest (5–18). Species richness, diversity, and abundance were positively related to the cover of habitat-forming corals, which was higher on protected seamounts (3%) than trawled seamounts (0.1%), but lower than on natural seamounts (52%). Invertebrates (including corals) were identified and counted at 25 seamounts from videos transects (up to 4.7 km long, from 1,100 to 1,400 m depth; 38 transects in total). Ten seamounts were located either in continuously trawled areas or in areas where trawling had stopped following establishment of reserves (at some point between 1997 and 2003), and 15 were in never-trawled natural areas. Fishing history of individual seamounts was verified using logbook data from the Australian Fisheries Management Authority.
(Summarised by Anaëlle Lemasson)