PSA : Waters are warm, and trout can suffer for it

Hey all,

There was a post recently about an angler who may have caught a trout in too warm of water (and then exposed it to warm air for too long) that they took down, likely because everyone and their brother shows up to get their .02 in. I did too, but I did so to try and share some info…

So anyway, I figured I'd collect a couple interesting articles from that post and drop them here for the interested anglers.

https://www.keepfishwet.org/keepemwet-news-1/trout-in-warming-waters

This is a recent study that challenges the "thresholds" that many of us are familiar with. Many people won't like this one but I think it's worth a read and considering. What I really like about this article, if you're reading closely, is that the author doesn't argue that 68F/20C is wrong, but that this number is often at the top of the range where mortality rates really kick into high hear. The author argues that different species have different mortality rates that start to increase exponentially above (5-10% per increase in degree) and that those thresholds are likely lower than we see on usual graphics around the internet.

• For those that do not want to go read it, and I would really recommend it, the author states the following thresholds (please, remember that threshold is not the limit, but the start of the exponential increase in mortality rates…)
  • Brown Trout : ~66F/19C
  • Rainbow,Steelhead,Cutty,Brook : ~61F/16C
  • Bull Trout : ~54F/12C

https://www.sciencedirect.com/science/article/pii/S0165783624000572

Another recent article/study was shared (it actually shares co-advisors in Dr. Danylchuk and Dr. Cooke, for whatever that might be worth). Shoutout to the redditor the shared this with me, although he seemed to be doing so in argument which was odd.

This one only studies rainbow trout and makes a strong case that the combination of water temps and handling (extended air exposure + dehooking time) lead to higher mortality rates. This one is more of a quantitative approach than the first, but I think ultimately they are saying very similar things. That catching fish in warm temps can lead to higher mortality rates. Anglers that practice catch and release should be aware that research lends support to the idea that :

1. if we lower the acceptable temperature thresholds for trout we'll lower mortality rates.
2. If we reduce the fight time and air exposure (faster dehooking and, yes, less photo sessions) as temps rise we'll lower mortality rates.
3. being species aware is key as different trout vary in their abilities to tolerate different temps, etc.