A REVIEW OF THE DIET AND ECOLOGY OF THE LONGNOSE VELVET DOGFISH CENTROSCYMNUS CREPIDATER (CHONDRICHTHYES: SOMNIOSIDAE) POPULATION IN THE ROCKALL TROUGH (NORTH-EAST ATLANTIC) AND AN ANALYSIS OF INTRA-POPULATION DIETARY VARIATION

• Main Author: Cronin, Elizabeth
• Other Authors: Faculty of Science
• Format: Thesis
• Language: unknown
• Published: University of Plymouth 2007
• Subjects: Rockall Trough; North East Atlantic
• Online Access: http://hdl.handle.net/10026.2/1025

The re-examination of the diet of the potentially vulnerable squalid Centroscymnus crepidater in the Rockall Trough region of the NE Atlantic has been conducted. The main prey types consumed have varied little temporally with a large importance of teleosts (particularly myctophids) and cephalopods. Identification of cephalopods consumed by C. crepidater to genera was conducted for the first time, and revealed a heavy reliance on teuthids; particularly Gonatus sp. The feeding strategy of this species was also revaluated. Results suggest a reasonably opportunistic feeding mode, likely to relate partially to prey availability and seasonal changes. The possibility of scavenging particularly on fisheries waste has been highlighted. The relatively low diversity in the diet and lack of variation in trophic levels between C. crepidater and co-occurring squalids led to the need to examine possible strategies to minimise inter-specific competition for food, with a particular emphasis on the Centroscymnus genus. lntrapopulation dietary variation was also examined for the first time in this species. This revealed a shift in preference from myctophids to cephalopods with size and maturity, largely attributed to the ability to catch larger, more 'profitable prey' with growth. This was concomitant with increasing trophic diversity and the proposed ability to be more opportunistic with growth. The hypothesis that with growth there is also the ability to be more selective; particularly in areas of higher prey abundance has been examined. Strategies to minimise competition for food within the C. crepidater population may exist, including proposed niche created by the need to repetitively feed on myctophids in smaller individuals. Although habitat variations may also play a role in diet and minimisation of intra-specific competition I this does not appear to be as important as varying capabilities with size. Faculty of Science