Diet of the spiny lobster Jasus paulensis from the Tristan da Cunha archipelago: Comparisons between islands, depths and lobster sizes

摘要

Diet of the Tristan spiny lobster Jasus paulensis was examined using gut content and Stable Isotope Analyses (SIA) to assess whether diets differed among three islands in the Tristan da Cunha archipelago (Inaccessible, Nightingale and Tristan islands), and between small and large lobsters at two depth intervals. Gut fullness was significantly less at Nightingale Island, suggesting overall less food there. Diet differed significantly among all islands, depths and sizes, although multidimensional scaling (MDS) and constrained canonical analysis of principle coordinates (CAP) plots showed considerable overlap and variability in diet. Lobster diet from Tristan Island showed a greater within-island similarity and was significantly less diverse, suggesting a more impoverished reef and narrower feeding niche, while dietary differences between size and depth reflected prey availability. Carbon and nitrogen stable isotope signatures differed among the islands, and carbon signatures between depths. Jasus paulensis appeared to be an opportunistic omnivore, with diet reflecting impoverished reef habitats. In addition, our data showed no evidence of soya remnants in the gut contents or tissue signatures of lobsters at Nightingale Island, following a soya spill there four years previously. However, gut fullness was less at Nightingale. This may have increased the attractiveness of baited traps, possibly explaining an observed rise in CPUE after the spill.