A blonde ray Raja brachyura
MBA scientists have shown for the first time how skates make night-time forays into shallower water. This unique window on the fine details of fish behaviour was made possible by data from electronic tagging, and may influence the management of these vulnerable species.
The skate species in the study were blonde ray (Raja brachyura), thornback ray (R. clavata), small-eyed ray (R. microocellata) and spotted ray (R. montagui). MBA researchers analyzed the data from 89 tags from recaptured skates. Combining the results with their knowledge of skate ecology, a credible picture of previously unknown migratory behaviour emerged in which skates move across a varied seabed topography, searching and foraging for food along the way.
The exact reasons for these journeys remain a mystery but the study rules out some explanations, for example optimizing body temperature. PhD student and co-author of the paper Samantha Simpson said, “It seems most likely that the movements we observed are foraging trips. What makes this research significant is that it points to skates travelling to shallower feeding grounds and returning to deeper resting grounds, akin to central place foraging-A behaviour not previously observed in these species.”
An understanding of populations, movements and preferred habitats of skates is of increasing importance given the documented declines in many skate populations. Lead author Nick Humphries added, “Observing animal behaviour in the sea is difficult and we know surprisingly little about the fine-scale activities of commercially important species such as skates. Our research suggests that marine protected areas should be large enough to encompass these movements and that fishing controls should consider the nature and timing of activity that likely makes the skates more susceptible to capture during the night in either trawls or set nets.”
Find out more about movement ecology and conservation of marine predators at the Sims Lab web pages.