Feeding selectivity in Notothenia coriiceps and N. rossii (Pisces, Nototheniidae) on amphipod species at Potter Cove, South Shetland Islands, Antarctica

SEEFELDT M.; QUARTINO L; VALLI FRANCIONE M.; BARRERA-ORO E. 2016; MOREIRA E.; SCHLOSS I

Kuala Lumpur

Congreso; SCAR OPEN SCIENCE CONFERENCE XXXIV, Kuala Lumpur, Malasia; 2016

SCAR

In inshore waters of the western Antarctic Peninsula and the South Shetland Islands, among the organisms of the benthic community ingested by fish (e.g. amphipods, polychaetes, bivalves, gastropods, cephalopods, chitons, isopods, echinoids), amphipods of the Suborder Gammaridea are the energy-richest taxa of the benthos. Furthermore, these organisms constitute the main food during most of the year for fish of the Suborder Notothenioidei, including the black rockcod Notothenia coriiceps (NOC) and the marbled rockcod Notothenia rossii (NOR). In contrast, other benthic components of very low energetic value (e.g. algae, sponges, corals, asteroids, ophiuroids, ascidians) are much less important fish prey. Despite their ecological resemblances and in line with their distinct body shape and morphology, NOC is more demersal and sedentary feeding mainly on a wider range of benthic organisms, whereas NOR is more semipelagic and migratory, feeding more regularly than NOC on water column prey. There is a high occurrence of amphipods (up to 85% of the total macrobenthos) in macrobenthic communities along the western Antarctic Peninsula. In this area of the southern Scotia Arc, including Potter Cove, King George Island/Isla 25 de Mayo, macroalgae colonized the sublittoral rocky shores and are extremely abundant in terms of biomass. They constitute natural habitat for amphipods and other invertebrates, being brown algae species with large bushy blades (e.g. of Order Desmarestiales) a suitable refuge from predation and/or environmental stress. Likewise, numerous mobile invertebrates, including amphipods, feed on small benthic diatoms among the macroalgae. In Potter Cove from the last three decades, due mainly to the effects of climate change, the retreat of the Fourcade Glacier has created newly ice-free areas available for benthic colonization. At the same time these areas have been exposed to high loads of sediment input from subglacial waters. Nevertheless, it was revealed that these new ice free areas are indeed a suitable site for macroalgal colonization. Thus, the community of macroalgae and associated fauna could have been expanded at Potter Cove ecosystem according to new hard substrate available for colonization. Due to the importance of gammarideans as prey of several fishes, it has been indicated that food competition would seem to be high in Potter Cove. However, different fish species may feed on different gammaridean species resulting in a low food overlap; for example, amphipods among macroalgae and epibenthic gammarideans. In the South Shetland Islands and western Antarctic Peninsula area only a few studies have been conducted on feeding selectivity by notothenioids in relation to food availability in the wild. Using samples obtained in Potter Cove, close to the scientific station Carlini (62⁰ 14?S, 58⁰ 40?W) in February-March of 2016, we carried out a comparative analysis of the benthic amphipods found in the fish diets with those collected along a depth gradient in rocky bottom with macroalgae. This allowed us to determine the degree of feeding selectivity 1) on different amphipod species; 2) between two morphological distinct notothenioid species.