Population aspects of two highly migratory sharks in East Pacific Ocean

Abstract

494 individuals of blue and mako shortfin sharks, caught as by-catch in the swordfish long-line fisheries, were studied during March 2005 until December 2006. Two arbitrary zones was established (oceanic and coastal) in a geographic range between 21º-35ºS and 77º-118º W. It was found that the abundance of the two species was higher in the coastal area rather than the oceanic zone. A possible explanation of these pattern of distribution might be due because coastal areas are characterized by a higher primary production and plenty of nutrients; therefore the amount of food is high, and also was observed that costal zone had an increment in the juvenile abundance of shortfin mako and then it is possible infer these spaces could be breeding-zone for this species.