hardon posted a url for a good Landline story aired last year,...

hardon posted a url for a good Landline story aired last year, here is an excerpt that might provide some info. These sorts of teething problems would be expected considering this sort of controlled spawning is relatively new but Steer seems to suggest they will be ready for it next time and take measures to prevent it.

Thanks again to hardon......

KERRY STAIGHT: Ironically, it's a prominent fisherman who could hold the answers for taking pressure off stock. Wild tuna have made Haguen Steer one of the wealthiest men in Australia. While he's not turning his back on his fishing business...it's what's in these tanks that he's banking on in the future. These young, rather nervous fish, are the first southern blue fin tuna in the world to be bred in captivity.
The history-making hatchery at Arneau bay near Port Lincoln houses 24 brood stock that way up to 180 kilos. Scientists tweak the conditions in the holding tank to induce spawning.

MILES WISE, CLEANSEAS TUNA: We can see the female moving up, male behind and now the cloud of sperm being released behind over the eggs that she's trailing out from the front.

KERRY STAIGHT: So then what actually happens?

MILES WISE: The marine eggs are buoyant so these eggs are going to float on the surface. They've been fertilised. In the wild they drift free, for here we collect them, move them to the hatchery and move them to tanks.

KERRY STAIGHT: Clean seas tuna, a public company which Haguen steer started, has already been successful at propagating king fish. In March last year it had a breakthrough with tuna when the first southern blue fin hatched. This year it's gone on a spawning frenzy.

HAGEN STEHR, CLEANSEAS TUNA: The fish spawn for 35 hours nonstop. We were shocked actually what happened. We weren't ready for. It I'm going to be really honest right now. We only got two tanks and so we had to dump lot of eggs. We could have been commercial legally. If we would have had the complex ready to accommodate all the eggs.

KERRY STAIGHT: Instead, scientists have used the spawning as an intense study session. One challenge is to stop the fast-swimming fish colliding with the sides of tanks. Another problem is the baby tuna have a tendency to eat each other but Haguen steer is confident they now have enough knowledge to take the next step.

HAGEN STEHR: If you get those fish into the sea after 20 days in the hatchery, by Easter we could maybe pull out fish of two to three kilo.

If you get them by the millions, you can restock. You put it back into the ocean. This is an absolute perfect sustainability cycle......

Full transcript at:

http://www.abc.net.au/landline/content/2008/s2663962.htm