Collection and descriptions of juvenile tunas from the central pacific

Abstract

Collections of juvenile tunas during the period 1951–1960 from the central Pacific are recorded. Juveniles of Neothunnus macropterus (Temminck and Schlegel), Katsuwonus pelamis (Linnaeus), and Auxis sp. are described and figured. Initial results with the British Columbia midwater trawl, as modified for collecting tuna forage organisms and juvenile tunas, suggest that this trawl has considerable promise as a collecting device. Its ability to catch juvenile tuna appears much greater than that of the 10 ft Isaacs-Kidd midwater trawl. Although much has been learned in recent years abouth the biology of adult tunas, we still have very little information concerning the occurrence, distribution, and habits of their postlarval and juvenile stages. This lack is due mainly to poor success in collecting the young with the methods hitherto used, i.e., dipnetting at night-light stations, midwater trawling with small and medium-sized nets, seining with tuna bait nets, and searching the stomach contents of adult tunas and other pelagic fishes. Most of the juveniles recorded in the literature have been reported from scattered localities and have come either from the stomachs of pelagic fishes (Kishinouye, 1919, 1923, 1924, 1926; Inanami, 1942; Marr, 1948; Eckles, 1949; Shimada, 1951a; Yabe, Anraku and Mori, 1953; Yabeet al., 1958) or from dipnetting at nightlight stations (Schaefer and Marr, 1948a, 1948b; Wade, 1949, 1950; Shimada, 1951b; Klawe and Shimada, 1959). Since tuna juveniles are taken sporadically, generally in small numbers, it is important that all known captures be recorded so that the information will be available to investigators.