Abstract:
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.