Can Fish Read a Thermometer?

Here are a couple of thoughts to ponder when the fish are not biting. They call it “fishing not catching,” therefore becoming a better catcher means research, study, and practice…“there are no free rides.” Secondly, temperature has a direct influence on the comfort level of fish and “Happy Fish…Make Happy Anglers.”

Therefore, understanding water temperature is perhaps the single most significant matter between fishing and catching. Appreciation of temperature and its affect on fish often makes your angling life simpler.

Fish are cold-blooded or presumed cold-blooded. Then again, like most creatures they do produce limited forms of metabolic heat derived from oxidation or burning of food. This might prompt the question; if they produce heat why are they cold-blooded? Cold-blooded simply means dependent on surrounding environments as there is no way of controlling the body’s temperature.

To understand why fish feel cold to the touch means knowing how their circulatory system operates. This very simple system circulates blood through a two-chamber, single pump heart which carries blood and oxygen to and from the gills. Since the gills are open to external temperatures and considering that blood passed through them makes it easy to grasp the cold-blooded concept. Any heat whether metabolic or otherwise rapidly dissipates as it enters and leaves the gills.

Although we consider all fish cold-blooded there are some exceptions. Tuna, billfish, and some sharks use a system of parallel blood vessels called “countercurrent heat exchange.” With this system the veins run close together and allow the transfer of heat from one to the other. In other words, veins carrying warm blood to the gills transfers’ heat to veins returning with cool blood. This system operates with remarkable efficiency allowing otherwise lost heat to remain within the body.

Tuna are a prime example of “countercurrent heat exchange” and it’s used so effectively you could refer to them as warm-blooded. Tuna have large muscles that require heat to function effectively. With a semi-constant body temperature their muscles contract faster which increases speed; enabling them to catch food, and escape danger.

Bodily functions in cold-blooded fish are temperature dependent and being unable to control that temperature any sudden changes can affect their appetite, heart rate and respiration. The only alternative to controlling an unbearable water temperature means they must move to more comfortable surroundings.

Temperatures typically fluctuate slowly, allowing fish the opportunity to gradually adapt to changing water temperatures.  However, severe cold fronts often force rapid drops thereby initiating uncomfortable and stressful conditions. Humans are no exception and uncomfortable circumstances often influence our activities or patterns of behavior. Subsequently when fish become comfortable they may instinctively move from a comfort zone to feed, provided they can return. On the other hand when they become uncomfortable, their patterns may also change transitioning them into a survival mode, becoming lethargic or not feeding; often moving to more tolerable temperatures until acclimatized. Clearly, fish are appreciably in touch with their surrounding especially temperature. In addition, the more you study their preferences, the more success you enjoy.

The metabolic processes increase as water warms and decreases as it cools. A 10 to 18 degree rise in water temperature causes metabolic rates to double often affecting feeding and digestion. However, extremes on either side can be devastating since water that are to cold or hot have a direct correlation to oxygen levels. In most cases, cold water slows them down and warm water speeds them up but only to a point. Rapidly fluctuating water temperatures frequently impair breathing consequently; oxygen rich waters with steady temperatures are more comfortable.

Because temperature affects everything most creatures including humans have comfort ranges. Comfort ranges for some Florida fish are: Snook 70-86, Redfish 56-84, Cobia 68-86. King Mackerel 70-75, Spanish Mackerel 67+, Pompano 70-86, Spotted Seatrout 65-75, Tarpon 74-88 These temperature ranges are only a guide and variations one-way or the other are expected.

Improving catch ratios is often the discussion among anglers but until you become skilled at reading the water; along with understanding temperature, habitats, and how each affects behavior patterns; pretty much all it is… just discussion.

Highly regarded lines of attack to becoming a better catcher are research and understanding. Remember, education should consist of a desire for knowledge raising an individual to a higher level of conscious comprehension.

What’s the Temperature Tip: Today’s electronic packages usually include provisions to monitor horizontal surface and often vertical temperature readings. Understandably, many anglers cannot afford these pricey tools. Here is an easy solution if you are not equipped with electronics, a simple everyday thermometer will suffice simply attach it to a string or secure it inside your live well.

Capt. Woody Gore    813-477-3814   www.captainwoodygore.com