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An End to Seafood by 2050?

26 June 2014

ISRAEL - A new study has uncovered the reason why 90 per cent fish larvae are biologically doomed to die mere days after hatching.

"An end to seafood by 2050?" "Fish to disappear by 2050?" These sensational media headlines were the result of a 2010 report by the United Nations Environment Program, declaring that over-fishing and pollution had nearly emptied the world's fish stocks.

The research, published in PNASand conducted at the Inter-University Institute for Marine Sciences in Eilat, Israel, suggests that "hydrodynamic starvation," or the physical inability to feed due to environmental incompatibility, is the reason so many fish larvae perish.

Survival strategies

"By focusing on the constraints placed on larvae survival, we have a better chance of producing higher quality mariculture," a specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, said Dr Holzman.

"If we can produce better fish, this will have huge implications for our ability to maintain fish populations."

Dr Holzman based his study on the problematic nature of fish reproduction. Nearly all fish species reproduce externally — they release and abandon their sperm and eggs into the water, providing no parental care.

The fertilized eggs then hatch in the water within a couple of days and the hatching larvae must sustain themselves.

When attached to a yolk sac (a membranous sac attached to an embryo that provides early nourishment in the form of yolk), these premature organisms can survive for a period of two or three days, but once the larvae, with poorly developed fins and gills, open their mouths, they start dying in droves.

"We thought, something is going on during this period, in which the proportional number of larvae dying is greatest," said Dr Holzman.

"Our goal was to pinpoint the mechanism causing them to die. We saw that even under the best controlled conditions, 70 per cent of fish larvae were dying within the two weeks known as the 'critical period,' when the larvae detach from the yolk sac and open their mouths to feed," said Dr Holzman.

"What was going on? We turned to physics as a source of the problem."

Further Reading

You can view the full report by clicking here.

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