Monday, January 30th, 2023
Monday, January 30th, 2023

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To fish or not: warm weather trout

By Jerrod Vila
Contributing Writer


This spring proved to be statistically cooler than most with ample precipitation. This, in turn, serves as the base for many trout fisheries across the state. However, as the transition from spring to summer occurs, catch-and-release trout fishermen should take a little extra care in returning their ever-so-sought-after prize to the waters in which they reside. 


Making an about face usually sometime in mid-September, water temperatures will begin to fall once again. But until that point, they are ever on the rise and something we as respectful anglers need to be cognizant of.


To make things clear I am not at all against keeping a few trout for the dinner table now and again; so if that is your prerogative, by all means keep a limit. It is hard to top a meal of fresh trout wrapped in foil, stuffed with butter and onions and done over the campfire. After all, it is tradition. What follows applies to the catch-and-release folk.


There are two distinctly different types of stream trout fisheries: freestone and tailwater. A freestone stream is defined as a flow that originates from the conglomeration of many smaller streams and grows with each influx to become a larger stream; the flow and temperature of the water contained within the system are solely characterized by snow-melt, rainfall, or any other naturally occurring water source. 


Tailwater systems, on the other hand, are typically found below a dam or a reservoir. Wherein there is a constant release of cold water. Hence keeping the entire system much cooler and ultimately rendering it ideal trout habitat throughout the duration of the year.


The mercury will climb in most freestone streams as the dog days of summer press on, in effect, becoming too warm to consciously and respectfully target trout in which the goal is to release. 


Tailwater fisheries are a completely different story however, and may hold cold, well oxygenated water throughout the duration of the summer months and trout may be fished for without worry of excessive stress due to warm water temperatures.


On the really hot days, the temperature swing may be as much as 10 to 12 degrees in a freestone stream. So in a nutshell, freestone streams may still be fishable very early on in the day after a period of cool nighttime air temperatures have brought them back down into the safe zone before climbing again around midday.


The trouble for many fishermen can be determining where to draw the line. When it comes to trout, how warm is too warm? The upper limits of the temperature range which trout will feed, grow and remain unstressed by thermal conditions certainly varies by species. The upper limits are characterized by the temperature at which trout, that are otherwise unstressed, will die should those conditions persist for a certain period of time (typically 24-48 hours). This number does not take into consideration a fish being hooked, and played where a buildup of lactic acid that occurs during the fight in conjunction with the lack of dissolved oxygen that may be too much for a fish to recover from.


Warm water contains less dissolved oxygen than colder water. As temperature increases and dissolved oxygen decreases, fish begin to experience stress. 


So how do you know when the conditions remain comfortable enough to fish your target stream without creating a lethal situation for its residents? Unfortunately, studies vary and there doesn’t seem to be any one set of accepted limits. That said, there is a considerable consensus that all three major trout species (brook, brown, and rainbow) begin to experience some level of stress at around 68 degrees, with that stress increasing rapidly as the temperature rises further. For brook trout, these limits are generally accepted to be a few degrees lower (some sources suggest as low as 65 degrees). For many fishermen, 68 degrees has become a pretty accepted figure that represents the “do not fish” limit if you plan on practicing catch-and-release.


Of course these are merely guidelines as water temperature is not the only determining factor of dissolved oxygen (speed of current also plays a factor for example). Trout which spend extended periods of time living on these generally accepted thermal margins will likely have a greater tolerance outside these margins. However, 68 degrees represents a limit, outside of which, as a responsible angler you should not target trout. Unless of course you plan on putting them on the dinner table; then water temperature really doesn’t matter at all. However, trout will be much less aggressive and in turn much harder to catch.


There are a few things an angler can do to assure the safest release possible. First and foremost, always use a net. Preferably one with a silicone rubber basket to keep from scraping away the protective slime coat found on all fish. As crazy as this sounds, it is honestly surprising to me to how many anglers I personally see streamline without a net. Even if you have intentions to keep fish, landing them is so much easier with a nice net. A net also serves as a good location to keep fish confined within the water for hook removal and to resuscitate for a minute or two if need be.


Another notable mention is to play and land fish as quickly as possible. Obviously this comes with a rather large gray area as every individual fish and scenario will differ. Using proper gear to effectively handle the size of fish expected to be encountered also helps. Maybe consider sizing up in tippet selection as the water warms so there is no worry when a little extra pressure needs to be put on a fish to get him into the net. 


We have all heard the catch phrase “keep ‘em wet.” Well this certainly applies to successful catch-and-release. While there is absolutely nothing wrong with holding up a nice fish for a quick photo, keeping them wet and out of the dirt and streamside gravel will do wonders for the health of a fish, reiterating the fact of why the use of a net is vitally important. 


Lastly, carry a pack-friendly thermometer with you. Even if you have to steal the digital meat thermometer from the kitchen, it will certainly serve the purpose. Take a reading when you first get on the water and a few more throughout the day. Chances are it will be a worthy addition in your trout fishing arsenal, aside from just discerning water temperature.


Hopefully these few tips will keep the fish alive, happy and able to be caught again!


Jerrod Vila pens a regular outdoor column in the Amsterdam Journal. 

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