Tank culture of yellowfin
tuna, Thunnus albacares: developing a spawning population for
research purposes
J.B. Wexler, V.P. Scholey, R.J. Olson, D. Margulies,
A. Nakazawa, J. M. Suter-2003
Aquaculture, 220(1-4): 327-35
Abstract:
A land-based culture facility for research on
yellowfin tuna, Thunnus albacares, was developed at the Achotines
Laboratory in the Republic of Panama. Six concrete tanks, and seawater and
life support systems were built to maintain a yellowfin broodstock. On
average, 50% of the yellowfin caught survived capture and handling, and
approximately 30% became broodstock in Tank 1 (17 m diameter, 6 m depth) or
Tank 2 (8.5 m diameter, 3 m depth). Each fish was tagged with a microchip
implant tag, then weighed, measured, and injected with oxytetracycline (OTC)
prior to stocking. Daily rations of primarily market squid, Loligo
opalescens, and Pacific thread herring, Opisthonema spp., were
regulated based on the feeding activity and energy requirements of the fish.
Feeding activity of the broodstock decreased when the water temperatures
decreased, and the fish ate decreasing daily rations and increasing calories
with increasing size. Spawning occurred in both tanks within 6–8 months of
capture. Spawning first occurred in Tank 1 when 24 females ranged in size
from 6 to 16 kg and 65 to 93 cm fork length (FL). Spawning was intermittent
during the first 2 months and occurred near daily thereafter. Tank size
appeared to affect survival rates, the types of mortalities that occurred,
and the growth of the fish. Survival rates after 1 year in captivity were
higher, and the fish were larger, on average, in Tank 1 than in Tank 2. Most
of the mortalities in Tank 1 were the result of wall strikes, which occurred
more frequently after the fish reached their highest density of 0.64 kg m-3
and sizes greater than 96 cm FL and 19 kg. Non-linear growth models were
fitted to the initial stocking sizes and final sizes of fish that died or
were removed from Tank 1 during 1996–1999. Estimated growth rates in
length (11–48 cm year-1) for fish between 51 and 150 cm FL
decreased with increasing length. Estimated growth rates in weight ranged
from 9 to 19 kg year-1 for fish less than 19 kg and 20–23 kg
year-1 for fish greater than 19 kg. The results of this work
demonstrate that the stable environment of a land-based culture facility may
be the preferred system for long-term maintenance of a yellowfin broodstock.