Journal Article

Reducing the short-term mortality of juvenile school prawns (<i>Metapenaeus macleayi</i>) discarded during trawling

William G. Macbeth, Matt K. Broadhurst, Brian D. Paterson and Michael E.L. Wooden

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 63, issue 5, pages 831-839
Published in print January 2006 | ISSN: 1054-3139
Published online January 2006 | e-ISSN: 1095-9289 | DOI:
Reducing the short-term mortality of juvenile school prawns (Metapenaeus macleayi) discarded during trawling

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  • Environmental Science
  • Marine and Estuarine Biology


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A field experiment was carried out in southeastern Australia to assess the short-term mortality and stress incurred by juvenile school prawns (Metapenaeus macleayi) discarded from an estuarine trawler. Some 35% of the prawns died up to 72 h after being caught in a trawl, exposed to air during sorting and separation from the retained catch (as per normal commercial procedures), then discarded into replicate cages. Total mortality was partitioned into that caused by trawling (about 16% of mortalities), and by subsequent sorting and grading (about 19%). Assuming that the majority of the non-penaeid bycatch is excluded from trawls (by the use of bycatch reduction devices), the latter mortalities could be almost eliminated by sorting and separating unwanted school prawns in water-filled compartments. Emersion stress was measured as concentrations of l-lactate in the haemolymph, which were elevated for at least 40 min following capture, but similar among all trawled treatments. l-lactate levels decreased within the first 24 h post-capture, then remained constant over at least the next 48 h, and were greater than baseline levels. The potential benefits associated with subtle changes to handling practices onboard estuarine trawlers are discussed.

Keywords: discard; estuarine fisheries; l-lactate; Metapenaeus macleayi; mortality; penaeid; prawn; square-mesh codend; stress; trawl

Journal Article.  5545 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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