Anyone have an undesrtanding of fish Biology.

[A Worm OOE]

A spokesman for PETA was claiming that, due to the suffocation that fish go through when out of the water, 40% die when returned. Obviously everything I have seen over the last 25 years tells me otherwise.

I was wondering however what exactly does happen to a fish when out of water. Presumeably, until the gills dry out the fish can breath.

Does anyone out there know exactly what the position is?

[craynerd]

AWOOE.....I am by now means an expert and can’t answer or comment on your 40% mortality rate but I may add a little more knowledge to your question - ""I was wondering however what exactly does happen to a fish when out of water?""

 

Basically as I understand gills are very delicate and have a very large surface area for gas exchange. Water has much less oxygen concentration per unit volume than air does; therefore the gills are essential in air filtration. To filter the oxygen from the water the gills use a contra flow / reverse flow system where blood passes in the opposite to that of oxygen diffusion. This is one major method of obtaining high oxygen concentrations, and is only possible due to the massive surface area. This surface area is obtained via the soft sponge like tissue of the gills. It is imperative that the gills are fully immersed in water to support the weight of the tissues if the gills go out of the water they almost completely collapse.

 

Thus the problem is not only asphyxiation but the collapsing of the gills.

 

There is however a second problem that if the gills dry out, the tissues will dry up and cause adhesion / sticking of joining cells/filaments. This proves a more serious problem as it is harder for the fish to reverse. This is why fish gills should be kept moist when out the water, not to provide more oxygen, as oxygen can only be gained when fully submerged but to inhibit filament adhesion.

 

In my own view, as long as the fish isn’t out of the water too long the gills should recover when re-submerged, and if the gills aren`t left to try I can’t see why the fish would die ! As for 40% dieing! I can`t see that, that’s saying that for every 100 fish caught in a lake a day 40 die, thinking of it like that, seems highly unlikely.

 

So there you go, just to put on a warning that that is how i interpret it (from research lol not just guess work) but i may have areas incorrect.

 

Regards

 

Chris

[Common 40]

craynerd:

AWOOE.....I am by now means an expert and can’t answer or comment on your 40% mortality rate but I may add a little more knowledge to your question -  ""I was wondering however what exactly does happen to a fish when out of water?""

 

Basically as I understand gills are very delicate and have a very large surface area for gas exchange. Water has much less oxygen concentration per unit volume than air does; therefore the gills are essential in air filtration. To filter the oxygen from the water the gills use a contra flow / reverse flow system where blood passes in the opposite to that of oxygen diffusion. This is one major method of obtaining high oxygen concentrations, and is only possible due to the massive surface area. This surface area is obtained via the soft sponge like tissue of the gills. It is imperative that the gills are fully immersed in water to support the weight of the tissues if the gills go out of the water they almost completely collapse.

 

Thus the problem is not only asphyxiation but the collapsing of the gills.

 

There is however a second problem that if the gills dry out, the tissues will dry up and cause adhesion / sticking of joining cells/filaments. This proves a more serious problem as it is harder for the fish to reverse. This is why fish gills should be kept moist when out the water, not to provide more oxygen, as oxygen can only be gained when fully submerged but to inhibit filament adhesion.

 

In my own view, as long as the fish isn’t out of the water too long the gills should recover when re-submerged, and if the gills aren`t left to try I can’t see why the fish would die ! As for 40% dieing! I can`t see that, that’s saying that for every 100 fish caught in a lake a day 40 die, thinking of it like that, seems highly unlikely.

 

So there you go, just to put on a warning that that is how i interpret it (from research lol not just guess work) but i may have areas incorrect.

 

Regards

 

Chris

chris, correct me if i am wrong but you seem to have plenty of scientific knowledge of fish but no idea how to catch one???

[craynerd]

lol, i am studying Pharmacology with a high GCSE and A level in Biology.

 

I know a lot about snooker and football, can`t play tho !!!! :-D

 

Regards

Chris

[chesters1]

i know lots about intrepids but but none of fish gills nor fish poisening but apart from the odd perch having died through sheer greed i find no dead fish after a match ,the pond has no pike (ok a jack was spotted) no crayfish and only a few middling sized perch ,any dead fish that MAY have died i will spot if they float and end up on the grid of the outlet (1 heron can only eat so many),if they sink theres nothing to eat them big enough to completly digest them all and if they rot on the bottom their swim bladders float and also will catch in the grid ,so from my own experience its rubbish.

the gills collapsing out of water may well aid the fish if they stick together then all that that will be open to the air will be the outside ends of the end gills and the edges not only will this (maybe) make up for the higher oxygen content of the air but also stop them drying out ,over to Bruno for the tech stuff,mind you in the few seconds their being unhooked and either put in a keepnet or released it would have to be furnace temperatures to dry the gills out

 

[ 22. February 2005, 07:45 PM: Message edited by: chesters1 ]

[Andrew Boyd]

Carp were transported in the 50's and 60's out of water. They were just wrapped in a wet sack and withstood several hours.

 

That being said, all fish should be returned to the water as quickly as possible, this is most important in the summer months when the warmer water does not hold so much dissolved O2.

[Leon Roskilly]

When I was a lad we would often take a couple of coarse fish home for the pot.

 

I remember a couple of large roach carried home wrapped in a cloth, that we transported from Sawbridgeworth to Leyton and which I put in a bowl of water to be cleaned, reviving and scary the wits out of my mum when they thrashed about in the bowl when she went near it!

 

They must of been out of the water for at least an hour!

 

TL - leon

[chesters1]

was the same for the mrs with a pike ,it had been in the creel for at least 3 hours with a headache it was winter and it was in a damp sack,she said it went for her throut as she washed it in a sink of cold water

 

[ 22. February 2005, 08:51 PM: Message edited by: chesters1 ]

[Vagabond]

Craynerd is right about the need for the gills to be kept moist - some fish are better built to achieve this - eg eels, catfish, and to a lesser extent carp and tench.

 

In the 50s I transported many carp in wet sacks from one pond to another - some made the journey direct, others spent a night in the bath en route.

 

Carp stocks in the ponds I stocked thrive to this day.

 

Consider too the evidence from many tagging programmes involving the fish spending some time out of water. Davy Holt's skate for one.

 

Marlin have been caught as long as five years after tagging and releasing. One was also caught half-an-hour after tagging, which shows its appetite wasn't harmed.

 

Although these fish would only be out of water for just a few minutes.

[kleinboet]

May I add a layman's views to this debate:

I would LOVE a PETA person to tell me that so I could tell them they are talking rubbish to their faces, preferably in public.

 

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. If PETA's claims had a shred of truth to them, surely 40% of these fish would be dead. On the contrary, these fish are caught, on a regular basis, over and over again.

 

PETA, if you are reading this, I think you better retract that statement before one of the angling organisations leave you penniless after a libel suit!

 

[ 22. February 2005, 09:52 PM: Message edited by: kleinboet ]