Feeding habits and dietary overlap in spiny dogfish Squalus acanthias (Squalidae) and narrowmouth catshark Schroederichthys bivius (Scyliorhinidae)

Abstract

Spiny dogfish Squalus acanthias and narrowmouth catshark Schroederichthys bivius are the only two shark species commonly inhabiting the Falkland Islands shelf. The present study was undertaken to investigate their feeding habits and possible dietary overlap between the species. The diet of the spiny dogfish was dominated by Falkland herring Sprattus fuegensis and squid Loligo gahi, though it also preyed on a wide range of other fish and invertebrates. Catsharks showed a preference for invertebrates. The diet of both species showed marked variations with season, and ontogenic shifts were also evident. Dietary overlap was minimal in winter (15·4%) and maximal in spring (61·1%), the latter being due to both species preying upon spawning aggregations of S. fuegensis.