Yellowfin Spawning

Yellowfin tuna in the main broodstock tank have been spawning almost daily since October 1996.  To our knowledge, this represents the only successful spawning of yellowfin in land-based tanks anywhere in the world.  Spawning can be intermittent during February and March, when offshore upwelling, induced by northerly winds of the dry season, brings cooler water temperatures near shore and into the rearing tanks.  Spawning generally occurs from early afternoon to late evening.  The spawning events are usually preceded by several hours of courtship behavior (paired swimming, chasing). 

Spawning sequence avi.   Click on image to put into motion
video clip (23.8 MB)

The numbers of fertilized eggs collected after each spawning event in the main broodstock tank range from several hundred to several million.  The eggs are collected by several methods, including siphoning and dipnetting at the surface and seining with a fine-mesh surface egg seine.  Fertilized eggs are hatched in 300-liter cylindrical incubation tanks.