Biological Observations on Shark Species Taken in Commercial Fisheries to the West of Ireland

Abstract

Abstract:During an investigation into the biology of three shark species commonly taken in Irish fisheries, biological information was also collected from an additional six less-common species: Galeorhinus galeus, Lamna nasus, Mustelus asterias, Galeus melastomus, Hexanchus griseus and Dalatias licha. Data on age, reproduction, feeding and parasites were collected from a total of 137 sharks. Age data from G. galeus and M. asterias suggest possible differences in growth-rate relative to other areas. The state-of-maturity of all specimens agreed with earlier studies, although data regarding the reproductive cycle of M. asterias and G. melastomus were inconsistent with data commonly reported for these species. Stomach contents were unremarkable, with the exception of 1.3kg of cetacean material recovered from a specimen of H. griseus. Results from the parasite component of the investigation extend the known range of two monogenean species, while a further three parasites were recorded from new hosts.