Feeding behaviour of the common dolphinfish Coryphaena hippurus: older fish use more complex foraging strategies

Abstract

The common dolphinfish (Coryphaena hippurus) is widely distributed and represents an important part of the currently exploited fishery resources. This species’ feeding behaviour, however, is poorly understood. This study aimed to investigate the feeding behaviour of dolphinfish and the effect of body size (and the consequently aggregated learning experience) on the strategies used for capturing their prey. Observations were made from an oil platform in north-eastern Brazil. Dolphinfish length was visually estimated and classified into three size classes. The following foraging strategies were observed in our study: ‘active chasing’, ‘leaping out’, ‘swimming in circles’, ‘surf’, ‘using floating objects’ and ‘cleaning turtle carapaces’. The most frequently used foraging strategy was ‘active chasing’, suggesting a strong preference of dolphinfish in using visual cues during predation. Smaller size-classes of dolphinfish did not perform the ‘swimming in circles’ and ‘surf’ strategy, probably due to a lack of learning experience, since further social interactions could be needed in order to show this strategy. Smaller dolphinfish regularly showed the ‘using floating objects’ as a foraging strategy, probably reflecting an opportunistic behaviour. The smallest individuals were using more simple strategies, to chase smaller prey that could have different and less complex escape strategies. It indicates learning experience could play an important role into the dolphinfish ontogeny, moving towards more complex foraging strategies throughout their lives. Independently of the age class, the dolphinfish displayed a varied repertory of foraging strategies, maximizing hunting success in the open ocean, a hostile pelagic environment with a low prey availability.