DISTRIBUTION OF LARVAL TUNAS IN MARQUESAN WATERS 



By Eugene L. Nakamura and Walter M. Matsumoto, Fishery Biologists (Research) 

 Bureau of Commercial Fisheries Biological Laboratory, Honolulu, Hawaii 96812 



ABSTRACT 



Spawning of tunas near the Marquesas Islands was 

 investigated by studying the distribution of larval tunas 

 collected in 1957 and 1958. Of the six species of larval 

 tunas identified, larval skipjack (Katsuwonus pelamis) 

 occurred most frequently. Prominent diel variation 

 with greater catches at night was observed at a station 

 occupied for 24 hours in December 1957 and March 1958 

 for larval skipjack and in January 1958 for larval yellow- 

 fin (Thunnus albacares). Both the incidence of the 

 capture of larval tunas and their abundance were 

 greater during the southern summer and fall (January 



to April) than in the other months of the year. There 

 was no difference in abundance of larval tunas with 

 respect to distance from shore, nor were there any 

 differences in abundance among the four transects 

 (north, east, south, and west of the islands) along 

 which sampling was conducted. No significant corre- 

 lation was found between abundance of invertebrate 

 plankton and larval tunas nor between schools of adult 

 tunas sighted and abundance of larval tunas. Tempo- 

 ral distribution of larvae ind-cated some spawning by 

 skipjack throughout the year. 



Oceanographic and fishing surveys in the Pacific 

 near the Marquesas Islands (fig. 1) during 1957-58 

 were part of a program undertaken by the Bureau 

 of Commercial Fisheries Biological Laboratory, 

 Honolulu, Hawaii, to investigate the tuna resources 

 in this area. Pertinent to this investigation was a 

 study of the time and location of the spawning 

 of tunas. 



Methods of determining spawning activities of 

 tunas involve inferences from studies of their ovaries 

 and the distribution of their larvae. The latter 

 method has been made possible by the identification 

 (tentative for some species) and detailed descriptions 

 of the larvae of skipjack [Katsuwonus pelmnis), yel- 

 lowfin [Thunnus albacares), bigeye (Thunnus obesiis), 

 albacore {Thunnus alalunga), bluefin {Thunnus thyn- 

 nus orienlalis), longfin {Thunnus tonggol), three 

 species of Euthynnus, and Auxis sp. (Matsumoto, 

 1958, 1959, 1962; Mead, 1951; Wade, 1951). At- 

 tempts to identify specifically eggs of these tunas 

 have been unsuccessful because of their similarity 



Note. — Approved for publication October 12, 1965. 

 FISHERY bulletin: VOLUME 66, NO. 1 



Figure 1. — Offshore survey track and the diel variability 

 station in the Marquesas, 1957-58. 



