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Marine Ecology Progress Series

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MEPS 449:41-54 (2012)  -  DOI:

Ecosystem effects of fishing on the continental slope in the Central Mediterranean Sea

Mark Dimech1,2,3,*, Michel J. Kaiser1, Sergio Ragonese4, Patrick J. Schembri

1School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey LL59 5AB, UK
2Malta Centre for Fisheries Science (MCFS), Fort San Lucjan Marsaxlokk BBG06, Malta
3Department of Biology, University of Malta, Msida MSD2080, Malta
4Istituto per l’Ambiente Marino Costiero IAMC/CNR Section of Mazara, Via Vaccara 61, 91026 Mazara del Vallo (TP), Italy

ABSTRACT: Fishing with demersal towed gears can have dramatic effects on the structure and functioning of marine ecosystems. We studied the ecosystem effects of the deep-sea red shrimp Aristaeomorpha foliacea trawl fishery (500 to 800 m) in the Strait of Sicily, at the population and community level by sampling in trawled and non-trawled sites as determined by vessel monitoring system (VMS) fishing effort data. The study was conducted within the Maltese 25 nautical mile Fisheries Management Zone as part of the ongoing MEDITS trawl survey. Samples were collected using an experimental otter trawl net with a cod-end stretched mesh size of 20 mm, from 7 stations located in trawled sites (mean depth 616 ± 26 m) and from 7 stations in non-trawled sites (mean depth 556 ± 40 m). Population and community indicators were compared across the trawled and non-trawled sites. Populations of A. foliacea and Etmopterus spinax did not show any differences in biomass between the trawled and non-trawled sites, whereas the biomass of Plesionika martia, Nephrops norvegicus, Helicolenus dactylopterus dactylopterus and Galeus melastomus was 4 times, 16 times, 6 times and 2 times higher, respectively, at the non-trawled sites. Changes in length structure were also detected for all species except for E. spinax. At the community level, higher biomass, density and diversity indices were recorded at the non-trawled sites. Despite the clear evidence of ecosystem changes due to fishing, the main target species, A. foliacea and P. martia, had a high resilience to trawling activities. Setting up trawling lanes as a management option would likely minimise negative impacts on species with slow growth rates and low resilience.

KEY WORDS: Strait of Sicily · Fishing impacts · Trawl surveys · Mediterranean · Demersal resources · Red shrimp

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Cite this article as: Dimech M, Kaiser MJ, Ragonese S, Schembri PJ (2012) Ecosystem effects of fishing on the continental slope in the Central Mediterranean Sea. Mar Ecol Prog Ser 449:41-54.

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