Effects of otter trawling on macrobenthos and management of demersal scalefish fisheries on the continental shelf of north-western Australia

Published source details Moran M. & Stepherson P.C. (2000) Effects of otter trawling on macrobenthos and management of demersal scalefish fisheries on the continental shelf of north-western Australia. ICES Journal of Marine Science, 57, 510-516.
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This study is summarised as evidence for the following.

	Action	Category
	Use a midwater/semi-pelagic trawl instead of bottom/demersal trawl Action Link

Use a midwater/semi-pelagic trawl instead of bottom/demersal trawl

A replicated, controlled study (date of study unspecified) in six seabed plots in the Indian Ocean, north-western Australia (Moran & Stephersn 2000) found that fishing with a semi-pelagic trawl did not reduce invertebrate abundance to the extent that fishing with a standard demersal trawl did. Following fishing with a semi-pelagic trawl, abundance of large sessile invertebrates (>20 cm) did not change and was similar to non-trawled plots, whereas following each fishing event with a demersal trawl their abundance was reduced by approximately 16% (data presented on a logarithm scale). The semi-pelagic trawl caught fewer commercially targeted fish than the demersal trawl. Two types of otter trawls were tested; a semi-pelagic trawl, deployed approximately 15 cm above the seabed (no contact), and a standard demersal trawl towed along the seabed (in contact). An area of seabed at 50–55 m depth that had never been trawled was divided into six 360 x 925 m plots: two plots/gear type and two non-trawled plots. Each trawled plot was trawled four times. Invertebrates attached to the seabed (>20 cm, reported as being mostly sponges, soft corals, and gorgonians) were counted from video camera recordings before and after each fishing event in trawled and non-trawled plots.

(Summarised by: Anaëlle Lemasson)