The “take-home message” is that newly-hatched tuna have to be fed the yolk-sac larvae of other species.
The multi-national Transdott tuna-breeding research program in Europe wrapped up a few weeks ago with a presentation of the latest findings. Nearly 50 scientists, researchers and breeders from Europe, the eastern Mediterranean, Australia and Japan attended the meeting.
Project spokesman Dr. Chris Bridges noted that some important lessons were learned from the Transdott project. The “take-home message” is that newly-hatched tuna have to be fed the yolk-sac larvae of other species. Breeders need to have on hand quantities sufficient to feed the tuna from about Day 15 post-hatch, through until the juvenile tuna are weaned to dry pellet feed (a process that takes about 15 days).
In Europe, yolk-sac larvae of sea bream can be available in the required quantities. Bridges stressed that the five days or so needed to wean the fish onto pellets requires considerable patience. In some cases it’s necessary to starve the juvenile Bluefin Tuna (BFTs) for a day or so, to make them hungry enough to eat the pellets.
Bridges said attendees at the wrap-up heard from representatives of the successful Northern Pacific BFT project at Japan’s Kinki University that they use parrot fish for yolk-sac larvae rather than bream.
“In Japan they always have these parrot-fish broodstock set up so they can manipulate them to produce yolk-sac larvae (at the right time) for the tuna,” he said.
Bridges also said that in Malta and Turkey work is about to start on experimenting with frozen yolk-sac larvae because the challenge is production of larvae as they’re needed.
Bridges is hopeful that in future breeders will be able to get tuna to spawn 12 months a year using photo-period and water-temperature manipulation.
He also spoke of the possibility of eventually finding a way for the cryogenic freezing of tuna eggs which would “revolutionize” tuna aquaculture.
– Quentin Dodd