Swordfish heat eyes to hunt

[LHPfish]

don't know if anyones read this article

Swordfish heat their eyes for the hunt

By Emma Young
NewScientist.com news service

Swordfish heat up their eyes to improve their tracking of fast-moving prey in deep, cold water, suggests a new study. Researchers already knew that certain large ocean predators - such as swordfish, tuna and some sharks - keep at least their eyes and brains warmer than the ambient ocean temperature.

But this is the first convincing biological explanation for why, says the team led by Kerstin Fritsches at the University of Queensland, Australia.

In laboratories onboard research vessels in the Pacific Ocean, Fritsches and her colleagues took freshly caught swordfish and immediately removed the retinas. They varied the temperature of the retinas from 5°C to 25°C and exposed them to light flashes of different frequencies, at a range of intensities. They found that temperature had a big impact on the retinas' ability to distinguish between individual flashes, using measurements of the retinas' physiological response.

Swordfish usually maintain the temperature of their eyes and brain at between 19°C and 28°C. Depending on the diving depth of the swordfish - and so the ambient temperature and intensity of light - this improves their ability to track their prey by up to ten times, says the team.

"Swordfish inhabit a virtual desert, with few sources of food scattered over huge distances. When they do come across extremely fast and highly manoeuvrable prey - such as large flying squid - the ability to pick up fast movement will significant increase their chances of catching their prey," says Fritsches.

Seven times better
It is not clear exactly how keeping the eyes and brain warmer prevents a deterioration of their vision. "But a temperature drop must affect transmission speed in nerves and other molecular and neurochemical processes, slowing the whole nerve response down," Fritsches says.

It is common to find swordfish in the Pacific Ocean at a depth of 300 metres. At this depth, the ambient temperature could be as cold as 3°C. A swordfish retina kept at 20°C at this depth would be seven times better at resolving moving images. The greatest benefit of having warm eyes would be when the water is cold but brightly lit.

In swordfish, a part of one of the muscles that moves its eyes has adapted to produce heat instead. It warms up the blood, which is then moved towards the eye and the brain. Other fish, such as tuna, keep their whole bodies warm. And similar light experiments by the team with retinas from freshly caught tuna suggest that warming also confers a visual advantage in these species.

Since all bony fish that warm themselves heat their eyes and brain, the adaptation is probably to prevent any debilitating effects from fast temperature changes to the nervous system - and the effect on the speed of vision is probably the most noticeable of these, Fritsches says.

[Relentless33]

Awesome article!!!

[LIGHTS OUT]

Had heard about it but thanks for the details.

[Fishalways]

The real qeustion is, how can we apply this information to catch more fish??

[snooknreds2]

Originally Posted by Fishalways

The real qeustion is, how can we apply this information to catch more fish??

ive already been thinking about that.

and i have a crazy idea!!!! let you guys know if it works after my next trip

[miamiangler1]

Interesting article ,, some thing to think about ...

[snooknreds2]

my other idea was to bring a microwave with you on the boat and just nuke the bait for a min or two b4 sending it down

[miamiangler1]

Originally Posted by snooknreds2

my other idea was to bring a microwave with you on the boat and just nuke the bait for a min or two b4 sending it down

Hummm < well that would cook the squid to much ... use the micro wave to boil water ... then heat up the squid for a 1 min... that might work..my idea was to use heat packs that you use for your gloves when skiing

[snooknreds2]

Originally Posted by miamiangler1

Hummm < well that would cook the squid to much ... use the micro wave to boil water ... then heat up the squid for a 1 min... that might work..my idea was to use heat packs that you use for your gloves when skiing

hhmmmmm.............

[hawgdawg]

I'm not sure if I read the article correctly, but what does heating up a squid have to do with the eyes of a swordfish being warm? Am I missing something here?

[LIGHTS OUT]

Originally Posted by hawgdawg

I'm not sure if I read the article correctly, but what does heating up a squid have to do with the eyes of a swordfish being warm? Am I missing something here?

My thoughts exactly. The article is geared towards a sworfishes ability to better its own vision by heating it's eyes and brain(not thermal sensing like a snake). Either way, I guess it never hurts to try something new.

[snooknreds2]

i was just messing around......

[Uncle Buck]

Hmmm... the "chicken bone chumline" seems to attract 'em. Maybe it's the warmth?

[billspilingup]

Originally Posted by Uncle Buck

Hmmm... the "chicken bone chumline" seems to attract 'em. Maybe it's the warmth?

I've had best results when throwing over bones with Texas Pete brand hot sauce. Publix is good but the Texas Pete usually leads to multiple fish nights.