Behaviour of Southern sea lions in presence of killer whales during fishing operations in Central Chile

Abstract

The killer whale is an opportunistic top-predator of ecosystems worldwide and its diet varies locally and seasonally, which is reflected in diverse feeding behaviours associated with its prey. We report the occurrence of killer whales presumably predating on southern sea lions associated with the jack mackerel fishing fleet in central Chile. The presence of killer whales was recorded during 4 fishing sets. All sightings consisted of 3-5 individual pods of females and calves. The number of sea lions was not significantly affected by the presence of killer whales, but their behaviour was, by reducing the number of behavioural displays, as they stopped feeding and resting activities and stayed close to the hull of the vessel after net retrieval ended. We propose that killer whales could be using the fishery as an indirect source of prey to benefit from the aggregation of sea lions around the vessel, far away from land.