Discards of the Spanish fleet in ICES Divisions

Abstract

Objectives: 1. To estimate the discards of commercial and non-commercial species, including pinnipeds, cetaceans, sea turtles and sea birds, incidentally caught by different fishing gears of the Spanish fleets in ICES Divisions. 2. To estimate of the total volume and/or number discarded by fleet in each ICES Division by scaling-up the results of the sampling programme using data on the fishing effort. 3. To obtain the size composition of the most significant species of discards of different fisheries unit. 4. To evaluate of the causes of discard procedures per fleet. 5. To evaluate of the impact of the fishing activity in each fishery unit in relation to the total biomass catches. Methodologies : A discard sampling programme, taking place during the year 1994, was applied based on stratified random sampling by fisheries unit. Fishing gears used were, Trawl, Long Line, Gill Net, and Purse Seine in the ICES Subareas: VI, VII, VIII and IX . Discards volume of all taxa, including target species and low or noncommercial interest species including marine mammals, marine reptiles and sea birds, were sampled and quantified by observers on board commercial Spanish fishing vessels. Results: In 1994 by-catches of marine mammals and sea turtles were no J recorded during the sampling period, and only 5 sea bird by-catches were seen by the observers. . The comparison of the fleets regarding their ratios of discards, in 1994 by Spanish fleets, shows that the larger percentages of discards relative to the total catches are produced in the trawler fisheries (about 35 to 59%). Conversely, purse seining in Division IXa and Subdivision Vlllc west show the lowest discard rates (1 to 6%). Long line (8 to 18%) gill net (25%) and purse seiners in Subdivision Vlllc East and Division Vlllb (4 to 30%) have asome intermediate amount of discards). If we analyze the results of total discards made by the fleet, it is trawling which produces the highest discard values (11 155 to 28 006 n, whereas gill net and purse seine In Divisions Vlllc and IXa produces a low volume (146 to 321 t). Total discard estimations for long lining and purse seiners in Subdivision Vlllc East and Division Vlllb show asome intermediate discard values (503 to 5 788 t) The reasons for discarding in 1994 produced by the Spanish fleet were basically: - the lack of commercial interest in many of the species caught, - the length of the trips which mean that it is not possible to maintain certain species on board, - the Spanish fleet's lack of quota for fishing certain species in certain zones, - the size of the individuals caught being below the minimum legal size and/or below the size with a commercial value, - individuals which deteriorate during the fishing process, - the hold capacity of the vessel which means that discards are produced, particularly in the case of purse seining and trawling in coastal areas, - the economic demands or decisions (marked fall in price due to the abundance of discards on certain days), - in low commercial value species, when the haul catch is very low, this species is discarded. Data from this study will be made available to ICES Working Groups on Assessment of Southern Self Demersal Stocks for Hake Megrim and Monks, on Assessment of Mackerel, Horse Mackerel, Sardine and Anchovy, on Assessment of Blue Whiting and in the Study Group on the Biology and Assessment of Deep-Sea Fisheries Resources.