One hundred and thirty-four deep-sea oblique-haul samples in Sagami Bay, central Japan, between 1968 and 1988, yielded 441 specimens of bathylagid fishes, mostly larvae, of the following five species:
Bathylagus ochotensis,
B. pacificus,
B. milleri, B. bericoides, and Leuroglossus schmidti. Of these,
B. ochotensis (n=372) was the most numerically dominant, followed by
B. pacificus (n=35),
B. milleri (n=18), L. schmidti (n=14) and B. bericoides (n=2) . Larval occurrences of these species exhibited clear seasonality, with
B. ochotensis being most abundant during November-April; in the other four species, such occurrences were restricted to several months,
viz. February-May in
B. pacificus, November-March in B. milleri, December-January in
L. schmidti and March in
B. bericoides, the data apparently reflecting annual synchronous reproduction. Sexually mature males and females were found only in two bathy-pelagic species
(B. pacificus and B. milleri) , although their occurrences, which were restricted to several months between July and December, barely overlapped those of their respective larvae (November-May overall). Furthermore, no immature adults of the latter two species, intermediate between the juvenile and mature adult size ranges (27-48 and 134-207mm standard length [SL], respectively), were collected, suggesting that they undergo ontogenetic migrations, either below the capture depths (>1, 200-1, 300m) or to more oceanic waters outside the bay (or both), until they attain sexual maturity.
View full abstract