Genetic monitoring for
spawning ecology of captive yellowfin tuna (Thunnus albacares) using
mitochondrial DNA variation
Y. Niwa, A. Nakazawa, D. Margulies, V.P. Scholey,
J.B. Wexler, S. Chow-2003
Aquaculture, 218(1-4): 387-395
Abstract:
Mitochondrial DNA genotypes of captive broodstock of
yellowfin tuna (Thunnus albacares) were compared with those of their
offspring in order to monitor spawning frequency and periodicity. Among 38
broodstock individuals, 27 genotypes were observed, 18 of which established
a single individual's identity. Spawned eggs and hatched larvae were
collected on 48 sampling days over a period of 1 year. Among 538 eggs and
larvae analyzed, 10 genotypes were observed; eight of them established a
single female's identity, and two types were shared by two females. The
spawning profiles of these females were determined by observing the
occurrence of these genotypes in the offspring. Based on the dates when
genotypes first occurred and on growth trajectories estimated for individual
fish, the size of a female at first spawning was estimated to be 12–28 kg
and 75–112 cm. Usually, multiple females spawned on a given date. The same
genotypes were observed on almost any sampling day throughout the year. The
results indicated that some individual females were capable of spawning
almost daily for extended periods of time as long as they remained in the
appropriate range of water temperatures and had sufficient food.
(INTEM
Consulting, Inc., 7-22-18-K201 Nishi-shinjuku, Shinjuku-ku, Tokyo 160-0023,
Japan,
e-mail of S. Chow: chow@affrc.go.jp)