A new report by researchers in Canada has come out recommending that fish caught recreationally which are released should not be kept longer than ten seconds out of water to ensure the best possible chances of survival.
The report, titled “Fish out of Water – How much air is too much?” is published in this September’s edition of Fisheries magazine, a publication of the American Fisheries Society.
A fish out of water is exposed to air and hence the term “air exposure” is often used. Scientifically, the fish suffers acute “hypoxia” (or “oxygen deficiency”). Gills collapse, the fish cannot get any oxygen into its body, carbon dioxide accumulates and the pH of its blood drops (meaning it becomes more acidic). The fish becomes significantly stressed, cells start to dies and eventually the fish dies, as we would if we held our breath too long.
In the report, the authors review much of the literature regarding air exposure thresholds for different fish species in both the commercial and recreational fisheries. They consider a number of factors that can influence how damaging air exposure is to a fish. For example, in general the more exhausted the fish is, the less air exposure it can tolerate, which makes sense. Try going for a hard run and then seeing if that affects how long you can hold your breath! Temperature is also important.
The report understandably tends to focus on Northern Hemisphere fish,but it is one of the few articles that actually recommends a time limit on how much air exposure a fish being caught recreationally can tolerate before damage starts occurring. It acknowledges that there are still gaps in our understanding, but believes an actual time limits needs to be recommended, rather than simply saying to minimise air exposure, which many other reports do.
From my point of view, I work very hard to get any fish I catch back into the water as quickly as possible if I want to let it go. I think most of the time it would be less than ten seconds; if I can, I release fish while they are still in the water which ensures there is no air exposure. People who have been fishing with me know this and sometimes find it frustrating, but I make no apologies. Spending a long time to get the right photo of a fish while it is essentially holding its breath is not justifiable, if the fish is to be released. If the fish is out of water, it’s either a quick photo or no photo at all, in my opinion. It is good to now be seeing more and more photos taken while the fish is still in the water.
So – interesting information. Thought I’d share it with you.
For anyone wanting to read the article, here is the reference:
Cook, K.V., Lennox, R.J., Hinch, S.G. and S.J. Cooke (2015). Fish out of Water – How Much Air is Too Much? Fisheries, 40: 452-461