Anyone have an undesrtanding of fish Biology.

[Ken L]

If they want to make a pseudo scientific statement, they should quote their sources or reviel the methododology that they have used to establish their figures.

I can see the headline now PETA kills 10,000 fish to establish angling mortality rate !

 

In short, they need to put up or shut up. Unless or until they do, there simply isn't a case to answer.

[twochay]

Bruno's ya man for this one.

[grumpybum]

"I can see the headline now PETA kills 10,000 fish to establish angling mortality rate !"

 

Thats exactly what peta would do. If I'm not mistaken there against any type of pet ownership, and there answer is to round up all dogs and cats then release them in to the wilds of Scotland????

[Eddie]

kleinboet:

The PROOF that I can produce is the big Carp that are caught, named, and returned to the water so that other anglers can catch the SAME fish, and regularly do.  

Ooh er mrs, Mr Waller's not going to like that, you've just elevated the bender of words and his telly watching mates above pike anglers (well they don't name their fish so are'nt as useful.

 

He'll have to say sir now whenever he rips the p***.

 

Wordbender the defender of angling.

[A Worm OOE]

Thanks for the replies guys.

My reason for asking this was that I wanted to have an answer when accused of sufocating fish when out of the water. The anacdotal evidence of the fish swimming of is fairly convincing to me but I wanted some science.

 

I did some research and came up with the same as Craynerd IE. that the gills contract and therefore are have less surface area to absorb Oxygen. I would have thought that, On the basis that there is a maximum of 5% disolved Oxygen in water, the fish should be able to survive with a 95% reduction in gill surface area when in a pure (ish) oxygen environment. That is as long as there is no damage to the gills from injury or drying. This is what my logic sugest but I would still like some sort of scientific back up.

 

As I said I just want some amo to counter what is one of the more obvious attacks made on anglers.

[Alan Stubbs]

As with all things living - they eventually die.

However, it goes to show the plethora of misinformation being put about by those who have a somewhat misguided axe to grind.

[Sheepy]

Atmospheric O2 is only about 20% so via the logic used a fish could cope with a 25% reduction in gill surface area

[GlennB]

A Worm On One End........:

Thanks for the replies guys.

My reason for asking this was that I wanted to have an answer when accused of sufocating fish when out of the water.  

Another counter to that argument would be the financial one.

Commercial lakes spend fortunes on stocking their waters with carp etc. If every angler who pays £5 for a day-ticket catches 10 fish, 4 of which die, the fishery would very soon go broke. But they don't go broke.

 

The Viaduct fishery here in Somerset has frequent matches, with winning weights of 100lb+ of carp being the norm. Call it 20 anglers x 10 fish of 5lb each, absolute minimum. 80 dead carp per match, according to the PETA figures. What would that cost the fishery owners to replace?

 

Plus, as has been mentioned, the lake would be thick with rotting fish carcases.

[StuMac]

Bizarre though it may sound - in chemical terms the concentration of oxygen in fully aerated water is the same as in the air above it. What is important is the 'partial pressure' which is about 160 mmHg at sea level. In a fast flowing stream (where the water is fully aerated), the partial pressure of oxgygen will be the same as in the air.

 

The problem is that oxygen diffuses through water a lot more slowly than it does through air, which is why you can have areas of a pond or river that are de-oxygenated.

 

This means that fish's gills must have water constantly flowing over them to extract sufficient oxygen to survive. The gills consist of lots of very fine filaments and, when these are out of the water, they clump together and so their effective surface are is reduced. This prevents them from extracting oxygen from the air. Some fish (lung fish, mudskippers can survive out of water because the can abosrb oxygen from other surfaces - the roof of the mouth I seem to remember.

 

The slow rate at which oxygen diffuses through water is also why we drown if immersed in sea water (there are other reasons why we die in freshwater - filling your lungs with freshwater is a lot more lethal than filling them with sea water).

 

When the lungs fill with water, the oxygen is removed from it by diffusion, but oxygen can't diffuse down into the lungs fast enough to allow the supply to be maintained, so you die of suffocation. There are some sythetic liquids which allow huge rates of oxygen diffusion, so you don't drown if immersed in them. I believe they are experimenting with using them to deliver Oxygen to the lungs of premature babies.

[GlennB]

Interesting article on anoxia (zero oxygen) tolerance in crucian carp, found at:

http://biologi.uio.no/genfys/groups/GN/pro_a.html

 

Anoxia tolerance and respiratory physiology of fish.(Principal invesigator: Professor Göran E. Nilsson)

"The Scandinavian fish fauna contains one truely remarkable fish: the crucian carp (no. Karuss; lat. Carassius carassius). This cyprinid fish is the most anoxia tolerant vertebrate known, being able to survive days without oxygen at room temperature and even months at temperatures close to 0 °C. Its anoxia tolerance is [almost certainly] an adaptation to surival in ice covered ponds that become anoxic during the long Nordic winter. Nilsson has for more than ten years studied the mechanisms that allows the brain of the crucian carp to survie periods of anoxia some 1000 times longer than other vertebrates."

 

Further on in the article they state that rainbow trout have no such tolerance.

 

How Nordic trout, pike etc survive the long winters I have no idea. Presumably they can only live in the larger lakes that never get totally oxygen-depleted? Or lakes that are fed by oxygenated streams below the ice cover?

 

Regards

 

Glenn