Abstract
We examined the diets of three size groups of the Pacific pomfret Brama japonica collected in April and May 2000 in the transition zone of the central North Pacific. Amphipods, cephalopods and fish werethree of the most common prey groups of pomfret. Of the three size groups, small pomfret (11.0-19.9 cm standard length (SL)) preyed mainly on amphipods and occasionally on cephalopods (mainly transitional species Onychoteuthis borealijaponica) and fish.(These prey amphipods and fish could not be identified to lower taxonomic levels because they were too digested.) Medium and large pomfret (20.0-30.9 and 31.0-40.9 cm SL, respectively) preyed mainly on cephalopods (mainly O. borealijaponica, but also on two subarctic species, namely Berryteuthis anonychus and Gonatopsis borealis), suggesting that these cephalopod species ensure energy for the northward migration of these two size groups in the transition zone in the spring. The next most common prey for medium pomfretwas amphipods (mainly subtropical species Phronima sedentaria and Platyscelus ovoides), followed by fish (mainly Bathylagus sp.). However, in the case of large pomfret, fish (mainly Paralepididae sp. ‘A’) were the next most common prey, followed by amphipods (mainly P. sedentaria and P. ovoides), indicating that the importance of fish as prey increases with growth for medium and large pomfret.
