Comparative study on feeding strategy and activity patterns of two Antarctic fish: Trematomus newnesi Boulenger, 1902 and Gobionotothen gibberifrons (Lonnberg, 1905) (Pisces, Nototheniidae) under different light conditions

Abstract

The behavior of Trematomus newnesi BOULENGER, 1902 and Gobionotothen gibberifrons (LONNBERG, 1905) (Pisces, Nototheniidae), caught in Admiralty Bay, King George Island, during the Antarctic summer, is compared. Experiments were done at 2℃ and two different light conditions. If both species are kept together in light for 24 hours, G. gibberifrons is usually more active than T. newnesi, swimming for longer periods, with higher speed, but showing lower respiratory frequency. An inversion occurs at 10/14 photo period. Rhythms may be observed in both light conditions for some behavioral patterns. If compared to G. gibberifrons the feeding success is 15 times higher for T. newnesi : it seems to detect shapes and movements at longer distances, swimming directly toward the prey, ingesting and swallowing at once. G. gibberifrons, in the presence of T. newnesi, takes a long time to react to the food and catches it only at the bottom, swimming through short jumping movements. If not in the presence of T. newnesi, it may catch the prey near the surface, with slow movements, but in any case food must be tasted inside the mouth before it is accepted as such. G. gibberifrons has more taste buds in the upper lips and in the pharyngeal region of the branchial arches than T. newnesi. The eyes seem better developed in T. newnesi. They are differently planced in both species, leading to different visual fields. One can conclude that when G. gibberifrons and T. newnesi share the same environment, behavioral strategies are developed to avoid each other.