Predator-prey relationship between the nototheniid fish Trematomus bernacchii and the Antarctic scallop Adamussium colbecki at Terra Nova Bay (Ross Sea)

Little information is available regarding predator-prey interactions in Hig h-Antarctic coastal systems. In this study, the predation of Tremtomus bern acchii (Pisces: Nototheniidae) on Adamussium colbecki(Mollusca: Pectinidae) is described and the related impact on the population structure of the mol lusc is hypothesized. Fishes and scallops were collected during several exp editions between 1990/91 and 1997/98 summers, in nearshore waters at Terra Nova Bay (Antarctica). Adamussium colbecki was the main food item of T. ber nacchii and an ontogenetic prey-size selection was observed. The predation was mainly on medium size classes of the scallop. These were lacking in the A. colbecki population sampled in the same period suggesting that the impa ct of fish-feeding on the size structure of the natural population of the m ollusc may be substantial. Two size classes of the Adamussium population we re not preyed on. Large adults avoid predation either because of the limits far mouth gape in the fish or by swimming avoidance capability, while smal ler scallops may not be preyed upon because they are attached through byssu s threads to very mobile large adults.