Ictiofauna demersal numa região de plataforma continental do sul do Brasil submetida à pesca camaroeira

Abstract

Ictiofauna demersal numa região de Plataforma Continental do Sul do Brasil, submetida à pesca camaroeira. A ictiofauna de uma região de Plataforma Continental do litoral do Paraná foi analisada objetivando comparar os atributos das espécies cujos indivíduos estão submetidos à pesca camaroeira com arrasto de fundo (profundidade 10m), com aqueles das espécies cujos indivíduos situam-se em área adjacente, sem atividade pesqueira (profundidade 15m). O material foi coletado através de arrasto de fundo, em 1999 e 2000, analisando-se sua composição, abundância e atividade reprodutiva. Entre as sessenta e duas espécies de peixes, 30 foram comuns às duas áreas, 24 exclusivas da área 10m e oito exclusivas da área 15m. A pesca camaroeira e seu conseqüente bycatch ocorrem numa área de Plataforma onde os atributos da ictiofauna são diferentes daqueles da área próxima. Incluem maior número de espécies exclusivas, maiores efetivos numéricos, maior atividade reprodutiva e espécies mais apreciadas para consumo. Os grupos cujos indivíduos são de bom valor comercial quando adultos (Clupeiformes e Sciaenidae) têm abundâncias mais regulares ao longo do tempo na área 10m que na área 15m; nesta, grupos sem interesse comercial (Haemulidae, Tetraodontiformes) predominam. Conclui-se que a assembléia de peixes da área 15m, onde pesca não é realizada, não dispõe de atributos biológicos (composição, atividade reprodutiva e outros) que pudessem neutralizar os efeitos impactantes causados pelo bycatch da pesca camaroeira na área adjacente. ABSTRACT A region of the Continental Shelf of Southern Brazil, isobaths 10 and 15 meters, was studied aiming to compare the attributes of the fish assemblage exposed to the shrimp trawl fisheries, to those of a fish assemblage from a contiguous deeper area that is not exposed to this fishing modality. Individuals were collected with bottom trawl net along 1999 and 2000, and its composition, abundance, size and reproductive activity were analyzed. Of the sixtytwo fish species, 30 were common to both areas, while 24 were exclusive to the fishing area and eight were exclusive to the nonfishing area. The shrimp trawl fisheries and the bycatch associated to it occur in a shelf area having very distinctive ichthyofaunistic attributes when compared to those found in the area where this type of fishing does not occur. These attributes include a high number of species exclusive to the fishing area, the formation of larger populational aggregates, a higher intensity of reproductive activity, a larger permanence of species with potential economic value, and a smaller mean individual size. There is evidence that many species do not reside in the study region, but are present because of their migratory behavior. Species whose individuals are valued commercially when adults (mainly Clupeiformes and Sciaenidae) present more uniform abundance values through time in the fishing area than in the contiguous area, where many important groups with no commercial interest (Haemulidae, Tetraodontiformes) were recorded. It is estimated that the ichthyofauna of the area presenting shrimp trawl fisheries is exposed to a disturbance that cannot be counterbalanced by the absence of this fishery activity in its contiguous area. RÉSUMÉ Ichtyofaune démersale dans une région du plateau continental sud-brésilien soumise à la pêche aux crévettes. L’ichtyofaune d’une région du plateau continental sud-brésilien a été analisée envisageant la comparaison entre les attributs de l’assemblage soumis à la pêche chalutière aux crévettes, profondeur 10m, et ceux de l’assemblage d’une aire adjacente, profondeur 15m, où il n’y a pas ce type de pêche. Le matériel a été prélevé en utilisant le chalut de fond, années 1999 et 2000, et leur composition, abondance et activité reproductive ont été évaluées. Parmi les soissante-deux espèces de poissons, 30 ont été communes aux deux aires, 24 ont été exclusives de l’aire 10m, et huit de l’aire 15m. La pêche aux crevettes et son conséquent bycatch de poissons ont lieu dans une aire du plateau portant des attributs ichtyofaunistiques différents de ceux de l’aire voisine, surtout des valeurs plus importantes d’espèces exclusives, d’effectif numérique, d’activité reproductive et d’espèces ayant un interêt commercial. Les espèces ayant une bonne valeur commerciale quand les individus sont adultes (Clupeiformes et Sciaenidae) ont des abondances plus régulières au cours du temps à 10m qu’à 15m, où quelques groups sans interêt commercial (Haemulidae, Tetraodontiformes) sont plus abondants. Il est proposé que l’absence de pêche au chalut dans l’aire 15m ne peut pas réduire les impacts que cette activité cause dans son aire voisine.

Temporal variation in composition, abundance and biomass of the fish fauna after impact on subtropical transitional water

“…The richness of the family Sciaenidae registered in the Saco dos Limões Cove is characteristic in tropical and subtropical transition environments in the Atlantic Ocean (Blaber, 2002). Other studies using bottom trawling in southern Brazil also point to greater richness for the family Sciaenidae (Kotas, 1998;Chaves, Cova-Grando, & Calluf, 2003;Godefroid, Spach, Santos, MacLaren, & Schwarz Junior, 2004;Branco & Verani, 2006). However, the most abundant species in number and biomass in the Saco dos Limões Cove were Genidens genidens, Eucinostomus gula and E. argenteus, which do not belong to the family Sciaenidae.…”