Cutlassfish

Abstract: Mercury (Hg), cadmium (Cd) and zinc (Zn) concentration were analysed in muscular and liver tissues of two cetacean species, franciscana Pontoporia blainvillei and boto-cinza Sotalia guianensis, in order to compare their contamination levels in northern Rio de Janeiro State, south-eastern Brazil. The cutlassfish, Trichiurus lepturus, which is the preferential prey of the boto-cinza, have also been analysed. Liver tissue always presented higher concentrations when compared with muscle samples for all the studied metals. The boto-cinza showed higher concentrations for all metals in both tissues than in the franciscana, and the only exception was Cd. This result is probably related to the difference in size prey preference of each cetacean. Mercury was the only element that presented significant positive correlations with body length and age in both cetacean species. The cutlassfish showed rising Hg concentrations with weight and total length, suggesting a possible mercury pathway for marine mammals' contamination.

Abstract: Background, aim, and scope At tropical latitudes, and especially on the semi-arid coasts of the Brazilian Northeast, the rainfall regime governs the water quality of estuaries due to the pronounced difference between the rainy and dry seasons. These changes may be responsible for seasonal changes in bioavailability of mercury (Hg) and other pollutants to the estuarine and coastal biota. Mercury bioaccumulates along estuarine–marine food chains usually result in higher concentrations in tissues of top predators and posing a risk to both marine mammals and humans alike. The Goiana River Estuary (7.5° S) is a typical estuary of the semi-arid tropical regions and supports traditional communities with fisheries (mollusks, fish, and crustacean). It is also responsible for an important part of the biological production of the adjacent coastal waters.

Abstract: The reproduction of the cutlassfish Trichiurus lepturus was studied from samples collected in bottom trawl surveys on the continental shelf and shelf break off southern Brazil. The mean total length (LT) at first gonadal maturity was 63.9 cm for males and 69.3 cm for females. Batch fecundity ranged from 3,917 in a specimen of 70 cm LT to 154,216 in a specimen of 141 cm but the number of spawning batches in each season was not established. Spawning occurs in late spring and summer in the continental shelf and probably year round over the shelf break. High surface temperatures and moderate stratification of the water column were associated with the final stages of gonadal maturation. Seasonal and spatial differences in sex ratios, sizes, maturity stages and feeding intensities suggest that adult female T. lepturus remain during the cold season in the continental shelf of southern Brazil to feed, while adult males move to warmer waters northward or offshore.

Abstract: Feeding habits of the cutlassfish, Trichiurus lepturus, in northern Rio de Janeiro. The aim of the present study was to describe the diet of the adult cutlassfish, Trichiurus lepturus, in northern Rio de Janeiro, through stomach content analysis. The sampling included 350 specimens measuring between 100 and 163cm in total length, collected from 2004 to 2006. For each prey species, the frequency of occurrence, density and biomass, body length and weight, and Index of Relative Importance (IRI) were calculated. The cannibalistic feeding behavior of the cutlassfish was also recorded. According to the IRI, the preferential prey species were the fishes T. lepturus, Pellona harroweri, Chirocentrodon bleekerianus, Lycengraulis grossidens, Peprilus paru, Chloroscombrus chrysurus, Odontognathus mucronatus, Stellifer brasiliensis and Isophisthus parvipinnis, and the crustacean Pleoticus muelleri. The cephalopods Loligo sanpaulensis and L. plei occurred occasionally in the stomach contents analyzed. The diet of T. lepturus in northern Rio de Janeiro was composed of pelagic and demersal prey species, associated with estuarine and coastal areas. The fish species and one crustacean species were the most representative items in its diet.