The capture of large amounts of small, immature fish of commercial species is a serious problem
particularly in multispecies fisheries. Moreover, considerable and increasing interest is being devoted by
fishery scientists to identify the distribution and habitat needs of species throughout their life cycle. To
elucidate species composition, the abundance of juveniles in the demersal assemblages and the role of
different life history (juvenile and adult) stages of target species in structuring demersal communities,
two bottom trawl surveys were carried out during the autumn 2003 and 2004. Multivariate analyses
were performed on density indices of adults and juveniles life stages of 30 target species and total
density indices for the remainder of the catch species. Juveniles represent more than 61% of the total
catch in both the years investigated and their abundance and spatial distribution was strictly related to
the sea bottom biocoenotic features. Most juveniles were concentrated in the coastal shelf area and in
particular in the hauls performed on the Coastal Terrigenous Mud biocoenosis (CTM). The demersal
assemblages located in the slope stratum showed, in general, a lower concentration of juvenile specimens;
however, some facies of the Bathyal Mud biocoenosis that characterizes the deep layer of our
study area showed a very high percentage of juveniles. This information improves our understanding of
ecosystem functioning and represents a useful basis for providing advice on the management of
multispecies demersal fisheries within an ecosystem approach.
The capture of large amounts of small, immature fish of commercial species is a serious problemparticularly in multispecies fisheries. Moreover, considerable and increasing interest is being devoted byfishery scientists to identify the distribution and habitat needs of species throughout their life cycle. Toelucidate species composition, the abundance of juveniles in the demersal assemblages and the role ofdifferent life history (juvenile and adult) stages of target species in structuring demersal communities,two bottom trawl surveys were carried out during the autumn 2003 and 2004. Multivariate analyseswere performed on density indices of adults and juveniles life stages of 30 target species and totaldensity indices for the remainder of the catch species. Juveniles represent more than 61% of the totalcatch in both the years investigated and their abundance and spatial distribution was strictly related tothe sea bottom biocoenotic features. Most juveniles were concentrated in the coastal shelf area and inparticular in the hauls performed on the Coastal Terrigenous Mud biocoenosis (CTM). The demersalassemblages located in the slope stratum showed, in general, a lower concentration of juvenile specimens;however, some facies of the Bathyal Mud biocoenosis that characterizes the deep layer of ourstudy area showed a very high percentage of juveniles. This information improves our understanding ofecosystem functioning and represents a useful basis for providing advice on the management ofmultispecies demersal fisheries within an ecosystem approach.
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