Assemblage characteristics and diet of fish in the shallow coastal waters of James Ross Island, Antarctica

摘要

This study presents data on fish assemblage structure for the relatively pristine and understudied Antarctic coastal zone (5-25 m). A total of 545 Notothenioidei and Bathydraconidae fish (eight species) were caught in the Prince Gustav Channel (James Ross Island, eastern Antarctic Peninsula) using Nordic multi-mesh benthic gill nets between January and February 2014. Trematomus hansoni dominated at 5 m and Trematomus bernacchii at 15 m, with Gobionotothen gibberifrons and Trematomus newnesi subdominant. Dominance at 25 m resembled that at 15 m. Despite relatively low numbers, species richness, abundance and biomass appeared to increase with depth. While T. bernacchii, T. hansoni, G. gibberifrons and Notothenia coriiceps all displayed multiple size (and probably age) groups, most T. newnesi ranged between 10 and 15 cm. Subsamples of G. gibberifrons and T. bernacchii showed a 1:1 adult/immature ratio, with minimum adult and maximum immature length/weight overlapping. Females outnumbered males, with a ratio of 2.8:1 for G. gibberifrons and 4.8:1 for T. bernacchii. The diet comprised mostly benthic taxa (isopods, gammarids, gastropods, polychaete worms). While G. gibberifrons appeared opportunistic, T. bernacchii specialised more on isopods. Our results highlight the possible importance of the Antarctic inshore zone as feeding habitat, despite frequent ice cover/scouring. We suggest that recent prolonged summer ice cover over the eastern side of the Antarctic Peninsula could have important impacts on inshore fish communities and food webs, though further in-depth studies are needed to confirm our results.