EVALUATION OF EFFICIENCY AND SELECTIVITY OF AN ENCIRCLING GILLNETS ("BOLICHEO") IN THE FISHERIES OF THE CIÉNAGA GRANDE DE SANTA MARTA, COLOMBIAN CARIBBEAN
A significant proportion of the annual commercial catch (27%) of the coastal lagoon Ciénaga Grande de Santa Marta, is obtained by encircling gillnets, called by the fishermen "Bolicheo". The utilization of this fishing gear is giving rise to conflict within the fishermen community, because its introduction increased the total catch of those few who can invert in this art, while the perceiving fisherman blame it of causing overfishing. To contribute with technical and scientific recommendations to reach a sustainable management of ichthyological resources selectivity and efficiency were evaluated using an experimental boliche with two mesh sizes (6.35 cm and 7.62 cm respective), during 20 working days carried out between october/93 and april/94. The fish captured were counted, measured and weighted, and the economical yield of each working day was determined. The total catch was 1285 kg, of 9281 individuals, to 18 species, with Eugenes plumieri (36%) as the species contributing to the highest biomass. The mesh size 6.35 cm caught 55% of the biomass and 63% of the abundance, the thus being more efficient than mesh size 7.62 cm. However mesh 6.35 cm was 34% less cost-effective than 7.62 cm, suggesting an economical advantage in the former. Applying Holt"s method, the selection parameters on 10 commercial species were obtained, which allowed the definition of appropriate mesh sizes to capture only mature fishes. It was concluded that fishing with boliche negative affect by some fish populations given that individual below medial mature size are being caught (80% in mesh 6.35 cm and 40% in mesh 7.62 cm). Hence, management action is required to regulate mesh size, for obtain the most cost-effective without affecting the resource renovation, according to the capture, effort and resource available, to obtain. Given that Mugil incilis, Cathorops spixii and E plumieri represent 80% annual catch, it is recommend to use mesh size 7.62 cm (3 inch), with the option of using mesh size 6.35 cm (2.5 inch) to capture M. incilis when it is abundant (october to december). However, is necessary to accompany this recommendation with other alternative means of livinghood for fisherman.
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