Know Your Water Temps
With negligible rain and temperatures consistently reaching 90s anglers must be aware of the effects this has on water temperature and the fish in these waters. Water temperature is an extremely important metric for fishing due to drastic changes in fish behavior caused by temperature fluctuations and even more important due to its direct relation to post catch mortality. Water temperature should be checked by every angler throughout the day when fishing primary in the hotter months but also in the dead of winter. Because fish are cold blooded their body temperature closely reflects that of the water in which they reside. The relation between Water temperature and a fish’s body temperature means that catch and release fishing should only take place in water between 35-64 degrees Fahrenheit (1.6- 17.7 Celsius) because a fish released in conditions outside that range has a much lower chance of surviving than one released within it.
During the coldest times of the year cold water will cause fish behavior to change, most predominately by drastically reducing their movement and feeding. The lowest end of the spectrum for cold water is clear, but even if the water has not yet become a solid that does not mean that fish and anglers have nothing to worry about. Water temperatures between freezing and below about 35 degrees will cause a sharp decrease in metabolism resulting in caloric shortage and stress that can prove fatal if a fish is suddenly forced to burn a large amount of calories when for example a fish is hooked and fighting to free itself.
On the other side of the scale, though an exact water temperature at which salmonids die is not known, and tolerances differ slightly between species, it is a commonly held belief that most salmonid species will die when water temperatures rise (and stay) above 77 degrees. Assuming 77 degrees as the absolute limit why would the high-end limit for safe fishing be more than ten degrees lower at 64 degrees? The answer here is due to increased molecular speed at higher temperature which allows more oxygen molecules to escape from water resulting in less dissolved oxygen being present in water. Under normal conditions a fish can survive in 64 degree water but because of reduced oxygen when that fish is put under stress (hooked and fighting to free itself) its ability to recover will be drastically reduced.
For more information on how to check water temperatures check out this post from Trouts: TROUTS TIPS: How-To Effectively Measure Water Temperature in Trout Streams
