In August, the researchers got five broodstock pairs of seabass to mate by making them believe it was winter. (Photo: Stock File/YouTube/FIS)
Researchers get seabass to spawn in summer
Thursday, October 28, 2010, 15:20 (GMT + 9)
Researchers at the National Institute for Oceanography and Fisheries in Alexandria (NIOF) have been experimenting with environmental conditions to stimulate the sexual desires of marine hatchery seabass. In August, the researchers got five broodstock pairs of seabass to mate by making them believe it was winter, or spawning season.
“It was the first time in Egypt to successfully spawn seabass during the summer,” said Mohamed Abdel Razek Eissa, head of NIOF’s aquaculture department.
Although the experiment must be replicated and perfected before it can go to commercial use, Egyptian hatchery operators may soon be employing the method to spawn marine finfish seed year-round and thus skirt the need to collecting wild fry, reports Al-Masry Al-Youm.
Currently, hatcheries supply less than 5 per cent of the fry used domestically as seed for aquaculture projects, meaning that over 80 million fry are collected annually from estuaries and lakes along the country’s northern coast.
This collection has fishers blaming the aquaculture industry for falling catches.
So as to help protect wild stocks, the government has come up with new regulations that ban gathering fry from the sea. It will go into force in 2013, and at that time all mariculture projects will have to use hatchery-raised fry as seed stock.
In light of the new regulations, researchers have been rushing to make broodstock spawn more frequently.
“We have just three years to increase our hatchery capacity,” said Eissa. “If we can spawn broodstock more than once a year, it would double or triple the amount of fertilized eggs.”
As Eissa manipulated the water temperature and lowered the lights inside the four fiberglass tanks holding the seabass, the simulated winter conditions tricked the fish’s brains into believing it was spawning season and spurring physiological changes.
Even though the five broodstock pairs produced the typical amount of eggs, only 110,000 of the 600,000 were fertilized. Eissa believes this occurred due to chemical imbalances caused by the unseasonal spawning.
However, he believes further experimentation could boost the fish’s survival rate.
Thus far, the high cost of refrigeration remains a larger problem.
“It is very expensive to decrease the air and water temperature during the hot summer months,” explained Eissa. “It is really only economical to induce seabass to spawn in the spring or the fall.”
Even spring or fall spawning would yield tremendous commercial value.
The researchers have also found that various marine finfish species employed in domestic mariculture spawn under “less intensive” conditions. Sea bream and sole spawn on their own in fall and spring, respectively, and become fertile in water temperatures circling 20C.
“They may be good candidates for summer spawning,” Eissa said.
By Natalia Real