SEASONAL OCCURRENCE OF DEEP-SEA BATHYLAGID FISHES IN SAGAMI BAY, CENTRAL JAPAN, WITH NOTES ON THEIR REPRODUCTION

One hundred and thirty-four deep-sea oblique-haul samples in Sagami Ba y, central Japan, between 1968 and 1988, yielded 441 specimens of bath ylagid fishes, mostly larvae, of the following five species: Bathylagu s ochotensis, B. pacificus, B. milleri, B. bericoides, and Leuroglossu s schmidti. Of these, B. ochotensis (n = 372) was the most numerically dominant, followed by R pacificus (n = 35), B. milleri (n = 18), L. s chmidti (n = 14) and B. bericoides (n = 2). Larval occurrences of thes e species exhibited clear seasonality, with B. ochotensis being most a bundant during November-April; in the other four species, such occurre nces were restricted to several months, viz. February-May in B. pacifi cus, November-March in B. milleri, December-January in L. schmidti and March in B. bericoides, the data apparently reflecting annual synchro nous reproduction. Sexually mature males and females were found only i n two bathypelagic species (B. pacificus and B. milleri), although the ir occurrences, which were restricted to several months between July a nd December, barely overlapped those of their respective larvae (Novem ber-May overall). Furthermore, no immature adults of the latter two sp ecies, intermediate between the juvenile and mature adult size ranges (27-48 and 134-207 mm standard length [SL], respectively), were collec ted, suggesting that they undergo ontogenetic migrations, either below the capture depths (> 1,200-1,300 m) or to more oceanic waters outsid e the bay (or both), until they attain sexual maturity.