Acronym RAI-AP-30/2004
Category
Fisheries
Title Pilot survey RAI/AP-30/2004 Programme National Programme
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source National Coordinator Enric Massuti Coordinator email enric.massuti@ba.ieo.es
Coordinator institution
IEO - Spanish Institute of Oceanography (Spain)
Institutions involved
NA
Start year 2005 End year 2006 Funding (€) € 44,900 Website http://www.repositorio.ieo.es/e-ieo/handle/10508/990 Summary From October 28th to November 28th 2005, 21 bottom trawls have been developed, between 113 and 796 m depth, on fishing grounds off South of Majorca (Balearic Islands, western Mediterranean), on board F/V Moralti Nou. A doubled extension piece trawl net has been used, with flexible sorting grids of 15 and 20 mm between bars, occupying ~75% of their surface, mounted in front of the codend, with an angle of ~40º. It is one of the first attempts in the Mediterranean Sea, which has allowed to assess, under commercial conditions, the efficiency of this kind of net and to estimate the commercial yields, the catch composition and the selection curves and parameters with both grids, for the main species exploited in the trawl fishery developed in the study area. Neither the net not the grids have showed any additional difficulty to the fishing commercial manoeuvres. No differences have been observed in the commercial yields with both grids. By contrast, differences in the percentage of retention for the main species were observed, with higher values with 15 mm than with 20 mm grid, allowing to escape smaller and larger individuals, respectively. The length of first capture estimated with 20 mm grid has been larger than with 15 mm grid. The sorting grids are not so efficient to improve trawl selectivity in the study area as the 40 mm square mesh in the codend previously showed. The sorting grids allow the escapement of larger individuals than the square mesh codend, but they have a lower percentage of escapement. For this reason, their selection curves show selection ranges wider and lengths of first capture lower than the square mesh codend. Moreover, a saturation effect of the sorting grids has been observed between 100 and 200 m depth. In conclusion, the sorting grids have not shown so effective as the square mesh in the codend. For this reason, a change of the mesh shape in the codend (from 40 mm diamond to square) could be a better management measure than the introduction of sorting grids to improve the selectivity of bottom trawls in the Balearic Islands.
The main objective was to evaluate the selectivity of bottom trawling gear with flexible separating grids on the continental shelf and the slope of Mallorca, as well as the profitability and viability of regular exploitation with these systems. The partial objectives that were proposed were: (1) To quantify the yields of the main target species of trawling on the deep shelf and upper slope of the study area (e.g. hake, Norway lobster Nephrops norvegicus, white shrimp Parapenaeus longirostris, blue whiting Micromesistius poutassou and pink shrimp) using selective flexible grids with 15 and 20 mm separation between bars; (2) Calculate the selection curves and parameters for these species with both grids; (3) Estimate the composition of the catch and discards with both grids; (4) Evaluate the feasibility of a routine use of selective flexible grids in commercial fishing maneuvers with trawling gear.
Keywords
Crustacean;
Shrimp;
Fishing technology;
Lobster;
Trawling;
Shellfish;
Hake;
Environmental impact;
Discard;
Gear selectivity;
Fish;
Marine Region
54
Balearic Island (GSA 5)
1
Marine Region Map
