Abstract
The trawl shrimp fishery on the coastal zone of Fortaleza county, Ceara State, Brazil is a year-round small-scale fishing activity that has been going on since 1983. This study was designed to study its by-catch by means of a sampling system carried out in 44 commercial trips amounting to 488.5 hours of effective fishing on board small-sized trawlers, from July, 1997 to June, 1998. Its main results are summarized as follows; (a) the by-catch was comprised of 97 species belonging to 44 families, among which Sciaenidae (12 species), Haemulidae (10 species), Carangidae (7 species) and Engraulidae (6 species) stand out; (b) the 14 species with higher frequency of occurrence accounted for 90.4% of total catch and the six species with high frequency of occurrence, for 68.6% of total catch; (c) the ratios of the by-catch weight to 1 kg of marketable shrimp were as follows: total weight = 3.28 kg, sorted out as 0.93 kg (28.6%) of potentiallymarketable species (fish and small-sized shrimp) and 2.34 kg (71.4%) of non-marketable fish species; (d) the trend variations of the estimated indices of diversity showed there to be a close monthly interdependence, with thew following mean estimates: species diversity, H’ = 2.610; equitability, E = 0.569; and species richness, D = 8.357; (e) a decreasing trend, with a geometric dependence, was found to exist between number of species in the by-catch and their specific numerical abundance.
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