Ecology of Moroteuthopsis longimana at the sub-Antarctic Prince Edward Islands, revealed through stable isotope analysis of squid beaks
Résumé
: Understanding the underlying ecological factors that affect the distribution patternsof organisms is vital for their conservation. Cephalopods such as giant warty squids Moroteuthop-sis longimanaare important in the diets of marine predators, including grey-headed albatrossesThalassarche chrysostoma, yet our understanding of their habitat and trophic ecology remainslimited. We investigated the habitat and trophic niche utilised by M. longimanathrough the δ13Cand δ15N profiles captured in their beaks. M. longimanabeaks were collected around grey-headed albatross nests at the Prince Edward Islands during 2004 and 2013 (n = 40 beaks). Theresults showed distinctly Antarctic distributions (δ13C = −24.0 ± 1.0 ‰, mean ± SD) for M. longi-mana, consistent with albatrosses foraging at the Southwest Indian Ridge, as opposed to broaderforaging zones utilised by albatrosses from Îles Crozet and Îles Kerguelen. Slightly lower δ15N val-ues (5.4 ± 0.7 ‰) were found compared to other islands in the Indian Sector of the Southern Ocean,which may indicate more crustaceans in the squid diets. Sequential sampling along the lateralwalls of individual beaks (n = 4) revealed ontogenetic shifts in δ13C and δ15N values, but individualvariation in these shifts requires further investigation.