This article first appeared in Mote Magazine, a quarterly publication by Mote Marine Lab.

Temperature
The subtropics are a great mix of characteristics of both the tropical environments to the south and the warm-temperate environments to the north.  A defining characteristic of the tropics is the relatively constant water temperature, which ranges from the upper 80s to the mid-70s, and in many locations not even this much variation.  In contrast, water temperatures in subtropical Charlotte Harbor typically range from the upper 80's in summer to the mid-50's in winter.  There can even be some abrupt changes in water temperature – particularly in winter when a cold front causes water temperatures to drop so quickly that fish may die of cold shock.

Due in large part to the overlap in temperatures between tropical and subtropical, and subtropical and warm-temperate regions, there is a considerable amount of overlap of both habitats and species.  So an angler’s knowledge of fishing in one environment will transfer to another.  For example, snook employ an ambush strategy to catch prey (waiting in the shadows of the mangroves for unsuspecting prey to pass by) throughout their range.  So an angler hoping to latch onto a large snook will do well by casting into the shadows of a mangrove-lined shoreline whether in southwest Florida or Belize. 

However, there are also many differences that an observant angler will incorporate into a fishing strategy.  These differences range from the way that similar habitats function to the behavior of some of the species of gamefish that range across different environments.  Again, using snook as an example – in south-central Florida, the northern limit of the snook’s range, snook will undergo notable seasonal changes in behavior (highest activity in warm summer months, and lowest activity, almost semi-dormant at times, in winter months), whereas seasonal differences and snook behavioral changes in Central America are minimal in comparison.

Cold-Blooded Fish
Since fish are cold-blooded, temperature is a controlling factor in their distribution. This is why you will generally not find snook north of Tampa Bay, nor striped bass south of northern Florida.  Each species has a range of temperatures that it can tolerate, and within this tolerance each species has a preferred temperature range.  Within its preferred temperature range, a species is generally most active, with more feeding, growth, and energy.  When the water temperature either exceeds or drops below the preferred range for a species, fish will often become lethargic. Learning the temperature tolerances and preferences for your favorite gamefish will go a long way toward helping you find locations, times of day, and seasons where you are most likely to find fish ready to take a well presented fly.

The preferred temperatures of gamefish are one of the helpful clues to figuring out why fish may bite one day and not the next, or may move from one area to another.  Fish are often able to tolerate extreme temperatures for short durations, but do best when in their comfort zone.   Adult snook are able to tolerate short periods of temperatures as low as 43oF, but long-term temperatures below 59o can be problematic.  Juvenile snook are not as tolerant of cold temperatures, having trouble when the temperature drops to 52o.  Snook generally don’t spawn until the water temperature approaches 78o, so temperatures between 75o - 85o might be considered the preferred temperature range for snook. 

Knowing the temperature preferences of your favorite gamefish is a good start, but there is a catch.  How a fish reacts to the temperature today is in part a function of what temperatures that fish was exposed to yesterday, and even for some time before.  Gradual changes taking place over days or weeks will influence a fish differently than a rapid temperature change in a day. Usually a slower change over time will result in better fishing, but sometimes a rapid temperature change will stimulate a feeding rush by gamefish.

Resident Gamefish
Red drum have a wide temperature range in which they will be active – from 50o - 82o, but seem to prefer water from the upper 50s to low 70s. Their behavior is reflective of water temperature, and is a variable you can use to improve your chances of finding active red drum on the flats. 

For example, in winter, when cool weather drops the water temperature into the low to mid 50's, red drum can become rather lethargic.  But if you find dark-bottomed flats, especially flats with some seagrass, and fish the right tide and time of day, you have a good chance of finding red drum on the feed.  On clear, calm days in winter, the sun will warm the flats considerably, especially if there is a mid-morning low tide.  A flat covered by water that is 55o in the morning can warm to 60o by early afternoon, and coupled with an incoming tide, can stimulate a period of feeding by the red drum that are on the flat.  Often the feeding will stop as quickly as it started, probably to allow the fish time to digest what they have eaten.  Since they are cold blooded, digestion also takes longer in these cooler temperatures.

Snook in the subtropics undergo a winter migration from their summer haunts in the estuarine shallows to areas where the water temperature is relatively constant.  Historically, in winter snook have sought out the constant temperature of freshwater springs in some of the coastal rivers and deeper areas in the estuaries, and more recently have also found refuge in the protected deeper waters of canals.  During warm periods in winter, some of these snook will venture into more open water to feed, which can make for some great fishing.

Migratory Gamefish
Other species of fish use a different strategy to remain in their preferred temperature range – they migrate.  Tarpon are a great example of a coastal species found in the subtropics that undertake seasonal migrations.  As tarpon migrate considerable distances to remain in their preferred temperature range, they encounter a variety of habitats and prey species, each with a different challenge – from coral reefs and seagrass beds in the south to temperate marsh in the north.  Each scenario changes the degree to which tarpon rely on different senses.  In clear tropical water, a tarpon has to be able to see the prey yet get close enough to capture it prey without being seen. In murky or tannin stained water, the tarpon might be able to rely on sight at only the closest distance, so sensing prey by vibrations and smell become more important. Each scenario requires a different approach from the angler as well.

All material copyright Aaron Adams 2007, 2008, and beyond, unless noted.