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Hot, cold or somewhere in between, so much of fish activity and their lifestyle is dictated by water temperature. There are other factors like moon phase and water quality, but surface water temperature is a great indicator as to what feeding mode they are in, where they will be located and what phase of spawning they might be in. In extreme temps it could be a matter of survival. Certainly, the geographical area you find yourself in may create a variance or make allowance for the fish’s tolerance levels. Northern spots or tropical warm weather locales may be all part of the adjustment the species may have made over hundreds of years.

High tech, Low tech or No tech.

With the advancement of electronics many variables appear on the screens of “fish finders”. GPS technology, depth, wind direction, underwater visibility and water temperatures all can be indications of natural influences. Some anglers ignore all the variables and just cast away blindly and hope to bet a bite. Others tap into the alignment of the electronics and search out or “scope” areas before presenting a bait. I’m somewhere in between. I visually search for clues as to the hideouts of whatever fish I have targeted but I do have a submersible thermometer to determine the surface water temperature in the area.

When the Spawn is On.

There is a large variance by species as to when they “go on bed” and the time period before that is known as pre-spawn. Pre-spawn is when you can catch massive numbers of fish but also lends itself to boating a BIG fish. Regardless of species they all feed heavily prior to the spawn in order to prepare themselves for the exhausting ritual of spawning. The appearance of many and certainly the bass family is drastically different after the feeding binge and then weeks later post spawn. *see photo. Not an exact science here’s a list of some of the most popular fish and their desired starting spawning temperatures. Smallmouth bass 59 degrees, largemouth 63, crappie 62 degrees, catfish 70 and bluegill are different in that their normal spawning behavior starts at 70 degrees and on the full moon, with additional spawning occurring on each full moon that the water is at 70 degrees! The moon does affect other species including the category of baitfish like shad and other minnows as well as many other wild creatures. Most fish DO NOT feed during the spawn but will vigorously defend their nests.


As a side note the digestion of our finny friends is in large part tied directly to the water temperature. A bass that eats a six-inch shad in 40-degree water takes around four or five days to digest the shad, same bass, same size shad in 78-degree water and the shad is digested in FOUR OR FIVE HOURS! The optimum digestive water temperature has been previously preached at around 75 degrees, recent studies document the highest rate of feeding and digesting is at 84 degrees.

When Slowdowns Occur.

The metabolism of most fish is in tune with water temperatures. In very cold water 45 and below they can go days without feeding and their movement can be minimized. Notorious cold-water species such a trout, walleye and others may continue a more normal rate of activity. Similarly, in very warm / hot waters (90 degrees and above) fish may slow down and become lethargic, feeding less frequently. This slow down is in direct proportion to the amount of dissolved oxygen contained in the water making breathing difficult. This is why there are often “die offs” that take place during the late, hotter summer months. In either case fish tend to become lazy until there is a natural correction.

Catch and Release.

If your goal is to release your catch during the hot water periods some extra precautions might favor a successful release. Keep in mind mishandled fish may still fall victim to delayed mortality, dying within a day of the release. In warmer environments fish that are played for longer periods can experience a build up of lactic acid (much like humans with a “Charlie horse”) have a full body experience, seize up and die. Play the fish in quickly, measure or photo, minimize the handling of the fish and gently release. Removal of the “slime coat” dooms a fish to a bacterial infection which most times is fatal. Tossing a fish into the air is also potentially damaging because the body of the fish is normally supported by water pressure and the air toss can be similar to a belly flop damaging internal organs.

Being aware of water temperature and its affects on the fish can be critical to the catch. Also being aware of your physical reaction to the outside air can keep you safe and comfortable. Dress for success, life jackets and being prepared goes a long way.