Journal Article

Burrow density and stock size fluctuations of <i>Nephrops norvegicus</i> in a semi-enclosed bay

C.J Smith and K.-N Papadopoulou

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 60, issue 4, pages 798-805
Published in print January 2003 | ISSN: 1054-3139
Published online January 2003 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/S1054-3139(03)00065-1
Burrow density and stock size fluctuations of Nephrops norvegicus in a semi-enclosed bay

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An underwater television technique was used to investigate burrow density of Nephrops norvegicus in a large semi-enclosed bay in the west central Aegean. Pagasitikos Bay has the shallowest occurrence of Nephrops in high densities in Greek waters with an estimated population area of 376 km2. As trawling is by law prohibited in the bay, Nephrops is fished only by bottom nets. Burrow densities were estimated seasonally (May, August and November 1998 and February 1999) by video sled transects at nine stations around the bay. Bottom trawls were undertaken to estimate animal abundance, mean individual carapace length and mean weight. Total stock estimate (number and weight) was undertaken for 100 and 75% burrow occupancy with the ground delimited by the 60 m contour. Annual removal by fishermen was estimated to be 1.5–2% of the stock. Densities were found to be higher than in other Greek Nephrops grounds. Variations in burrow density were found both between stations and within stations over time, with an overall decrease in density in 1999. The decrease in density during 1999, in conjunction with an increase in mean carapace length from the trawl catches was attributed to an eutrophication event evidenced by a flock layer settling onto the seabed and causing, in the worst cases, patches of anoxic surface sediments. The event was most probably the result of high nutrient run-off into the bay.

Keywords: Aegean; burrow density; Nephrops; underwater video; stock assessment

Journal Article.  4672 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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