A fishery associated with floating objects in the Indian Ocean off Southern Sri Lanka

Abstract

The present study was carried out from August 2007 to January 2008 in southern Sri Lanka to investigate the catch composition of offshore fisheries from multi-day boats. Some boats were engaged in flotsam associated surrounding net fisheries. The fish landings from 77 boats were classified into three categories: (i) only from surrounding nets (S), (ii) from surrounding nets plus drift gillnetting/longlining (SGL), and (iii) only from drift gillnetting/longlining (GL). The catch estimate in each boat trip was categorised into one of the three groups for every fish species caught.

The Indian scad, Decapterus russelli (Rüppell, 1830), rainbow runner, Elagatis bipinnulata (Quoy and Gaimard, 1825), common dolphinfish, Coryphaena hippurus Linnaeus, 1758 and starry triggerfish, Abalistes stellatus (Anonymous, 1798) contributed significantly to catches in S and SGL boats but were insignificant in the catches of GL boats. In flotsam-associated surrounding nets, juvenile tunas, skipjack, Katsuwonus pelamis (Linnaeus, 1758) and yellowfin, Thunnus albacores (Bonnaterre, 1788) (15-60 cm total length) were also caught. Multivariate statistical analyses revealed that fish catch composition from GL boats differed from that of S and SGL boats. The biological consequences of behavioural changes and vulnerability of fish stocks to overfishing due to aggregation around flotsam require further investigation.