Please note that we have updated this post because the study discussed has been misinterpreted and taken out of context. The importance of the Ferguson and Tufts 1992 study is that it was the first to demonstrate the potential magnitude of impact that air exposure can have on fish. HOWEVER, the numbers from that study are NOT meant to be representative of what happens in real fishing situations!!!! I cannot emphasize this point enough!
Sascha Clark Danylchuk
For the first Finsights translation I wanted to start with a classic manuscript about air exposure and fish, and arguably, the paper that started it all. The paper (linked here and at the bottom of this page) is titled “Physiological effects of brief air exposure in exhaustively exercised rainbow trout (Oncorhynchus mykiss): Implications for ‘catch and release’ fisheries” and was published in the Canadian Journal of Fisheries and Aquatic Sciences in 1992 by Ralph Ferguson and Bruce Tufts.
What did they do?
In this study, the scientists compared three groups of rainbow trout:
• Fish that were exercised
• Fish that were exercised and air exposed (for 60 seconds)
• A control group of fish that were neither exercised nor air exposed
Because this experiment was performed in a lab, chasing trout around the tank was used as a proxy for exercise, which is how scientists think of angling or fighting a fish.
They then measured a bunch of different blood parameters that are used as indicators of stress. I don’t want to go into the details of blood chemistry here – it can be confusing and I don’t think necessary to understanding the main points of this study – but I do want to point out that this is a very common way to look at the effects of angling on fish.
Lastly, the scientists looked at the survival of fish in each of the three groups and also added another group that was exercised and air exposed for 30 seconds, but where no blood samples were taken.
What did they find?
• Air exposure made a big difference!
• Rainbow trout that were air exposed were more stressed and exhausted than any of the other fish.
• More fish that were air exposed died compared to those that were just exercised.
Why didn’t the air-exposed trout survive? The scientists argue that the trout that were air-exposed died because fish gills don’t work in air. Gills consist of tiny, delicate structures, called lamellae, where oxygen exchange occurs. Water flow across the lamellae is essential for proper functioning and for a fish to breathe (oxygen in, carbon dioxide out…just like us). When fish are lifted out of the water, the lamellae collapse and stick together and the fish can’t get any oxygen.
Imagine running a marathon and then being forced to hold your breath – your body (and likewise that of an angled fish) would be deprived of oxygen at the precise moment that you needed it the most.