Evaluation of sorting grids for deepwater rose shrimp (Parapenaeus longirostris) in the Eastern Mediterranean demersal trawl fishery

Abstract

The study aimed to evaluate sorting grids of 10 and 15mm bar spacing specifically for separation of deep water rose shrimp, but including other species, in a Mediterranean multispecies demersal trawl fishery. Data were collected 15-25 October 2008 in Si?acik Bay, Eastern Aegean Sea with the commercial trawler, 'Hapulo?lu', using a modified bottom trawl net. A total of 22 valid hauls (12 with 10mm, ten with 15mm grids) were obtained. The separation rate of anglerfish was highest, with 100% for weight and number in both codends among all species. Grid elimination of broadtail short-fin squid showed differences between 95.3 and 80.3% in terms of weight, and 89.7 and 66.2% in terms of number for 10 and 15mm, respectively. Separation ratios for hake, silver scabbard fish, and horse mackerel were between 96.3 and 100% in terms of weight, and 92.2 and 100% in terms of number in both codends. Shrimp separation was in total calculated as 60.8 and 37.0% by number, and 70.7 and 44.4% by weight in 10 and 15mm bar spacing trawl grids, respectively, demonstrating that substantial improvement in species selectivity (deep water rose shrimp from others) is possible to achieve by adding sorting grids in the Mediterranean demersal trawl fishery. To optimize the overall selection performance in such fisheries, a variety of grid systems, bar spacings and materials as well as the economic consequences need to be evaluated. © 2011 Blackwell Verlag, Berlin.