Are Fish Near Extinction? – 06/30/2014

Are Fish Near Extinction?
by Staff Writers
Tel Aviv, Israel (SPX) Jun 30, 2014

[MC – Comment – Hmmmm, how did the fish survive for so long with this “biological flaw”? Is there something, maybe metallic and electro-magnetic, making their habitat water more viscous?
hmmm?]

Dr. Holzman based his study on the problematic nature of fish reproduction.

“An end to seafood by 2050?” “Fish to disappear by 2050?” These
sensational media Are Fish Near Extinction?s 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.

That scarcity portends disaster for over a billion people around the world
who are dependent on fish for their main source of protein.

Now, a new study by Dr. Roi Holzman and Victor China of the Department of
Zoology at Tel Aviv University’s George S. Wise Faculty of Life Sciences
has uncovered the reason why 90% fish larvae are biologically doomed to
die mere days after hatching.

With this understanding of the mechanism that kills off the majority of
the world’s fish larvae, leaving only a marginal proportion to populate
the world’s oceans, “We can help find a solution to the looming fish
crisis in the world,” said Dr. Holzman.

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% 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.”

Eating soup with a fork

The physical structure of the larvae and their flawed interaction with the
physical environment provided the answer Dr. Holzman was looking for. Over
the course of two years, he and doctoral student Victor China observed
fish larvae at three significant points in their development (at the
beginning, middle, and end of that “critical period” – eight, 13, and 23
days old).

They found that the “stickiness” of the water – the viscosity of the
surrounding ocean water – was hampering the larvae’s attempts to feed.
“All that determines the larvae’s feeding ability is viscosity – not age,
not development. Only their interaction with the surrounding water,” said
Dr. Holzman.

“Because the water molecules around you have weak electrical bonds, only a
thin layer sticks to your skin – a mere millimeter thick. If you’re a
large organism, you hardly feel it. But if you’re a three-millimeter-sized
larva, dragging a millimeter of water across your body will prevent you
from propelling forward to feed. So really, it’s all about larval size,
and its ability to grow fast and escape the size where it feels the water
as viscous fluid.”

The researchers found that in less viscous water, the larvae improved
their feeding ability. In theory, they can be expected to increase their
survival rate. “We conclude that hydrodynamic starvation is the reason for
their dying,” said Dr. Holzman. “Imagine eating soup with a fork – that’s
what it’s like for these larvae. They’re not developed enough at the
critical point to adopt the constrained feeding strategy of adult-sized,
better-developed fish.”

Armed with this knowledge of the larvae’s biological flaw, the researchers
are currently patenting a solution to maintain higher survival rates among
fish larvae populations.

Source: http://www.spacedaily.com/reports/Are_Fish_Near_Extinction_999.html