Fish distribution monitoring in the Lithuanian Exclusive Economic Zone, Baltic Sea: Implications to fisheries management

摘要

All data and samples used in this study were obtained from bottom trawl surveys conducted over the period 2000-2005 by research vessel R/V Darius (24 m length and engine power 300 HP small fishing stern trawler (SFST)) using otter trawl net with 120 mm mesh codend and 8 mm mesh liner in codend. Overall, surveys were performed seasonally at randomly stratified monitoring stations. Factors in terms of sediment type, depth range and season influencing species diversity, abundance and biomass of catches within Lithuanian Exclusive Economic Zone (LEEZ) were investigated. Length-age distribution of the most abundant and commercially important species, namely cod, Gadus morhua, flounder, Platichthys flesus, herring, Clupea harengus and sprat, Sprattus sprattus were analyzed. As a result, nursery areas for species mentioned above were detected and closed for fishery. The fish species studied here could generally be grouped into species living permanently in the coastal zone and species undertaking migrations between shallow zone and other habitats, only utilizing the coastal zone during some life history stages. Thus, north-eastern part of LEEZ was defined as an area where young individuals of herring, sprat, smelt and twait shad form rather dense schools. This closure box for fishery was introduced in 1995.