Elasmobranch electroreceptive foraging behaviour: male-female interactions, choice and cognitive ability

Aspects of electroreceptive foraging behaviour were investigated in a benthic elasmobranch, Scyliorhinus canicula (small-spotted catshark). The findings build on current knowledge of sexual conflict in this species and provide novel information concerning differentiation ability, choice and cognition relating to elasmobranch electroreceptive foraging behaviour. Hierarchical catshark behaviours towards artificial, prey-type electric fields (E fields) following stimulation by food-derived scent were recorded under laboratory conditions. Experiment 1: Male-female interactions Foraging behaviour of single- and mixed-sex catshark groups were investigated using electroreception as a proxy for feeding levels. Results indicated significant reductions in foraging levels of being grouped with the opposite sex, in addition to higher responsiveness in females. These attributes are most likely consequences of differing reproductive strategies and resultant sexual conflict. Experiment 2: Choice Catsharks were trained to swim through narrow tunnels and upon exit were presented with two differing E fields simultaneously. Choices were recorded and analysed, and thereby their ability to distinguish between and/or show preferences for fields was determined. Differentiation ability was demonstrated by preferences for stronger rather than weaker direct current fields, and alternating rather than direct current fields. The fish were either unable to distinguish or showed no preference for artificial (electrodes) and natural fields (crabs). Experiment 3: Cognitive ability Response levels and changes in response levels over time of catsharks rewarded for responding to E fields were compared to those of catsharks that were not rewarded. Results demonstrated learning and habituation behaviour improving foraging efficiency over short time scales according to profitability of fields. Failure to retain altered behaviour after an interval indicated short memory windows. These attributes would prove beneficial in a variable environment. Given many elasmobranchs’ continuing population declines and increasing potential interactions with anthropogenic E fields, such information will hopefully benefit both fisheries managers and offshore renewable energy developers.