Abstract

A new fishing technique, adapted from the artisanal trotline fishery for Patagonian toothfish (Dissostichus eleginoides) in Chile is described. The modified artisanal system, which includes a net sleeve that is placed on secondary vertical lines, has practically eliminated depredation of fish by killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus). The performance of this fishing technique with regard to seabird mortality and depredation by sperm and killer whales on fish catch rate was assessed during September-December 2006. The results were then compared with similar data obtained in 2002 in the same fleet in the same fishing grounds prior to the implementation of the modification. The number of seabirds killed in 2002 was 1 542 compared to zero in 2006; there was also a reduction in depredation of the catch from a maximum of 5% in 2002 to a maximum of 0.36% of the total catch in 2006. The fishers who developed the net sleeve modification called it 'cachalotera' (from 'cachalote' meaning sperm whale in Spanish). The term 'Chilean longline' is preferred in this paper because it was developed in 2005 in the Chilean toothfish fishery in the Magellan region.