Analysis of the stomach contents of 721 specimens of Scomber japonicus shows a feeding preference for three different items; copepods, mysids and fish. This feeding preference is influenced by habitat, seasonal fluctuations of the available food and the behavioural pattern of the prey species. The importance of mysids in the diet of immature and adult fish, in comparison with theirs importance to juveniles, show differences caused by habitat. On the other hand, fish are eaten, almost exclusively, during the first two quarters of the year. Scomber japonicus shows a predation on this item conditioned by the period of maximal abundance of fry in the area. Fish may feed on swarms of mysids taking advantage of their positive phototactic response to weak light sources, just as purse seiners use light to lure mackerel at night. This would explain the differences in the abundance of mysids between the stomach contents of club mackerel and data from sampling programs of zooplankton in the area. There are some aspects, however, that still remain unsolved.

SCIE

333

325

9