Distribution and abundance of the life stages of the blue shark Prionace glauca in the Southwest Atlantic | Bycatch Management Information System (BMIS)

Source URL

https://www.sciencedirect.com/science/article/pii/S0165783609002653

Citation

Montealegre-Quijano S, Vooren CM (2010) Distribution and abundance of the life stages of the blue shark Prionace glauca in the Southwest Atlantic. Fisheries Research 101:168–179. https://doi.org/10.1016/j.fishres.2009.10.001

Abstract

The composition and magnitude of the catches of the life stages of both sexes of the blue shark Prionace glauca were recorded at sea from 2004 to 2006 during seven commercial longline fishing cruises off Southern Brazil between latitudes of 24°S and 38°S and longitudes 29°W and 52°W. P. glauca occurred in all sets and constituted 63% of the pooled catch in numbers. Fork length (FL) ranged from 84 to 262cm in the males and from 73 to 247cm in the females. Sea surface temperature ranged from 16.2 to 28.3°C. The Subtropical Convergence (STC) of the Southwest Atlantic occurred in the sampling area from autumn to spring (June–December). Small juveniles (FL, 70–129cm) of both sexes were abundant only in the area of the STC. Of the large juveniles (FL, 130–179cm), males were abundant south of latitude 23°S and females were scarce in the entire study area. Of the small adults (FL, 180–219cm), males occurred in the entire study area without a seasonal pattern and females were abundant only in the summer (March) north of latitude 26°S. Large adults (FL, 220–262cm) of both sexes were scarce at all times. In analogy with the spatial distribution of the life stages of P. glauca in other oceans, the distribution patterns of the life stages in the study area justify the hypothesis that the STC comprises a nursery area of P. glauca in the Southwest Atlantic, where small juveniles of both sexes remain until they reach FL of 130cm. After that stage the large juvenile males disperse northwards, whereas the large juvenile females move to the south of the STC or to the Southeast Atlantic off Africa. The subadult females move northwards in late summer (March) to areas beyond latitude 25°S. Because of the limitations of the fishery-dependent data and patchy coverage of the study area, no definitive conclusions are presented, but the above hypotheses may orient further study of the spatial distribution of the blue shark in the Southwest Atlantic.