Summer feeding habits of the Pacific pomfret Brama japonica in the transitional and subarctic waters of the central North Pacific
Abstract:Feeding habits of the Pacific pomfret Brama japonica, ranging from 30 to 40 cm in standard length, were quantitatively evaluated using the index of relative importance and were compared between the transitional domain and subarctic region in the central North Pacific. In the transitional domain (between the subarctic boundary and the subarctic front), this species fed mainly on subarctic and transitional‐water gonatid squids such as Berryteuthis anonychus, Gonatus middendorffi and Gonatopsis borealis, the transitional‐water squid Onychoteuthis borealijaponica, and a subtropical and transitional‐water amphipod, Phronima sedentaria. These prey items accounted for 52·8% by wet mass of total stomach contents. In the subarctic region (north of the subarctic front), Pacific pomfrets preyed primarily on subarctic and transitional‐water squids, such as B. anonychus and G. middendorffi, and secondarily on subarctic amphipods such as Hyperia medusarum and Hyperia glaba. These four prey items comprised 71·6% by mass of total stomach contents. Major transitional domain prey items, such as G. borealis, O. borealijaponica and P. sedentaria, were almost non‐existent in stomachs of fish from the subarctic region. The mean wet stomach content mass expressed as a percentage of body mass was significantly higher in the subarctic region (2·35%) than in the transitional domain (0·75%), suggesting that, for this fish, prey items are more readily available in the subarctic region during summer and their northward migration is a feeding migration. Feeding strategy of the Pacific pomfret was discussed in relation to their seasonal south‐north migration.
Document Type: Regular Paper
Affiliations: 1: National Research Institute of Far Seas Fisheries, 2-12-4 Fukuura, Kanazawa, Yokohama 236-8648, Japan and 2: National Science Museum, 3-23-1 Hyakunin-cho, Shinjyuku, Tokyo 169-0073, Japan
Publication date: May 1, 2006