Section 27
Chapter 26,108

Yellowfin tuna spawning in the central equatorial Pacific

Yuen, H.S.H.; June, F.C.

U S Fish And Wildlife Ser Fish Bull 57(112): 251-264


Accession: 026107804

740 laboratory determinations of mature ovaries of Neothunnus macropterus caught in the central equatorial pacific, and field determination supplements furnished data for this investigation. The usual length at sexual maturity of yellowfin in this area was ca 120 cm, although yellowfin as small as 70 cm may be mature. Spawning occurred throughout the area surveyed (10[degree]N. to 8[degree] S. latitude, 120[degree] W. to 180[degree] longitude). Other studies have indicated that this area is but part of a band of yellowfin spawning grounds which covers the entire equatorial Pacific. Residual eggs in various stages of resorption are described. Of 25 ovaries examined, 22 were infested with unidentified nematodes 0.5-4 cm in length. Number of worms in an ovary was usually less than 5, and the infestation did not appear serious enough to affect the function of the ovary.

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