No abstract

The incidental capture of sea turtles by industrial shrimp trawlers off eastern Venezuela is documented, based on data gathered by on-board observers from February 1991 through November 2000. A total of 275 trips were made, with a total of 55,992 h of trawling using either one or two normal nets of 20-m headrope length, equivalent to 59,744 h std. net–1 of 30.5 m upper rope length. In total, 63 turtles were captured: 20 Eretmochelys imbricata, 20 Chelonia mydas, 15 Caretta caretta, and 8 Dermochelys coriacea. All these species showed a wide distribution along the central Caribbean Sea and Atlantic coasts of Venezuela, but they were always caught in areas close to shore and not deeper than 82 m; the distribution of D. coriacea was more concentrated towards the Atlantic zone. The estimated CPUE for all four species, using non-standardized effort values, was 0.0011 ± 0.0003 turtles h–1 std. net, equivalent to one turtle per 930 ± 11 h std. net. The variation in captures throughout the year was not significant (χ2 = 1.29; P = 0.73), except for D. coriacea, which was only caught between January and May. No significant difference was observed between the capture of turtles during the day or night. Direct mortality ratio reached 19 ± 9.7%; the actual ratio of mortality caused by incidental capture is not known. Most individuals caught by Venezuelan trawlers were juveniles that most probably use the area as feeding grounds. Considering an average effort by the fleet of 310,000 ± 16,500 h std. net yr–1, an estimate of turtle capture before the use of turtle excluder devices was made mandatory in 1994 would be about 330 ± 4 ind yr–1, with an associated direct mortality of 63 ± 30 turtles. This capture rate would be the lowest among the countries where similar evaluations have been performed (Australia, Colombia, Costa Rica, and USA). Key words: size structure, CPUE, distribution, Caribbean Sea.

<p>The delta of Orinoco River constitutes a long estuarine extension of a great importance to fisheries at Venezuela, because, it is an indispensable area for reproduction, feeding and growing of several fish species, most of them with a commercial application. The purpose of this research was to identify and analyze the changes in fish diversity and the structural dynamic of the community at four zones of channel Manamo, during dry and rainy season. Samples were taken on March and May for dry period and July and August for rainy season. A total of 48 species were identified, grouped into 24 families and 42 genera. The diversity was higher in Bajo del Medio during the dry season (2.58 bits/ind), decreasing to 1.66 bits/ind in el Pajar (rains). The PERMANOVAS analyzes showed statistical differences in the composition of species with respect to the climate season (psed-F = 0.0365, <em>p</em> &lt;0.05), but not between the sampling stations (psed-F 0.6668; <em>p</em> &lt; 0.05). The results indicated that the fish fauna of the region is composed of elements characteristic of an estuary, being the climate seasons the most important factors for the evaluated group and this reflects the seasonal nature of this community.</p>

Fishery and biometrics of genus Calappa crabs (Brachyura: Calappidae) in northeastern Venezuela. The box crabs, genus Calappa, are important crab species landed by the industrial trawl fleet in Venezuela. These crabs have a wide distribution in the country, from the Gulf of Venezuela to the Orinoco River, but major landings take place in such gulf, near Margarita Island and northern Sucre State. Average annual landing in the eastern region was 69 t during 1970-2001, with a maximum of 221 t. For this study a sample of 2 398 box crabs was collected by observers on board of industrial trawl vessels, which operated in eastern Venezuela from 1994 to 2000. Three species were found in the landings, Calappa sulcata and C. flammea, each represented 47% of the sample, and C. nítida, which accounted for 5% of the sample. Sex ratio was strongly biased towards males in C. sulcata (2.8:1) and in C. flammea (1.9:1), while it was only slightly biased in C. nitida (1.4:1). Due to its large size, C. sulcata is of great commercial interest, with average weight 290 g and a maximum weight of 720 g; C. flammea showed an average weight of 140 g and a maximum weight of 418 g, while C. nitida is the smallest species, with average weight 46 g and maximum weight not beyond 113 g. Box crabs were captured by day and night in similar proportions, and were found in a wide depth range, from a few meters to 126 m deep; however, the largest captures were obtained in the interval 38 -54 m. Regressions between weight of chelae and total weight were linear, and significantly different between sexes. The relation between total weight and carapace width was allometric, with a power exponent ca. three in C. sulcata, and less than three in C. flamea and C. nítida. Females of C. sulcata and C. nitida showed power exponents significantly smaller than males. Since claws are removed from the animal to be commercialized, while the rest of the animal is returned alive to the sea, for practical purposes a common equation among species and sexes to convert claws weight into total body weight is: total weight = 3 x claws weight. The relationship between catch per unit of effort (CPUE) and effort did not show a significantly decreasing trend, but landings follow the effort trend, with a decreasing tendency in recent years. No mature females were found in any of the three species, thus there could be reproductive migrations towards deeper waters from October to January, when abundance of crabs is lower in the study area. It is recommended that the practice of exploiting only one claw, returning the rest of the animal alive to the sea, should be promoted among fishers, while the removal of claws from female crabs should be avoided. Rev. Biol. Trop. 53(3-4): 463-474. Epub 2005 Oct 3.