カタクチイワシの摂じ生態 ＩＩ カタクチシラスの摂じ方法と食性

Abstract

In this paper, the composition, size and weight of gut contents of some 36, 000 anchovy larvae collected from Suruga Bay from 1968 to 1976 are treated, and the feeding habit in relation to their mode of feeding are discussed.Anchovy larvae eat infrequently, capture large-sized prey by the “biting lunge” behavior during the day, and are poor feeders. However, for those over 25mmTL., the 3 times increase in the maximum gut content length and the 2.5 times increase in the number of larvae that have the satiety indices of 20.1-40.0% are observed associated with the increase in the growth rates of the mouth and esophagus diameters. Hence, the feeding success of larvae improves with the development of the feeding organs, though their feeding mode is not changed throughout the larval stage. The feeding incidence and gut content weight reach the highest in summer when high water temperatures prevail in their habitat. These do not clearly correspond with the change in the zooplankton concentration in situ.In summary, it is considered that the food selectivity of anchovy larvae to prefer large sized plankton is a characteristic of the “biting lunge” behavior, and the feeding success will be increased, if concentrated large and seizable food organisms are available to them.