Subtropical Seasonality

In the previous articles in this series I provided an overview of some of the habitats anglers will encounter in the tropics B primarily the Caribbean and surrounding locations (Florida Keys, Bahamas, Turks and Caicos).  In later articles I may revisit some of these habitats, and the game fish you will likely find there, in more detail.  But with this article, the focus of the series will begin moving northward, into subtropical environments.  In North America, the subtropics occur in south Florida and in Mexico.

The subtropics are a great mix of characteristics of both the tropical environments to the south and the warm-temperate environments to the north.  This mix provides an opportunity to apply to this environment some of the information from previous articles, while introducing new concepts at the same time.  I will use this article to introduce one of the most important elements that helps define the subtropical and warm-temperate environments B seasonality B providing examples throughout.  In subsequent articles I will focus on some of the specific habitats and gamefish that make the subtropics such a great area to fish, and provide more details and examples.

Anglers fishing in warm-temperate environments that may feel left out should take heart.  Many of the gamefish, and some of the habitats, that I mention in this and the next few articles are also found in your area, so much of this information will apply to you as well. 

Seasonality    
A defining characteristic of the tropics is the relatively constant temperature.  In general, water temperature in the tropics may range 10 degree F to 15 degree F over a year, with highs in the upper 80s and lows into the 70s.  In many locations, there is not even this much variation.  This relatively stable environment results in habitats and species being present over a large area, which allows me to write a single article that is appropriate for the entire region.  This is not the case in subtropical regions, where water temperature can range 20 to 30 degrees over a year.

Due in large part to the overlap in temperatures between tropical and subtropical, and subtropical and warm-temperate regions with the changing seasons, there is a considerable amount of overlap of both habitats and species.  In that respect, some of an angler's knowledge of fishing in one environment will transfer to another.  For example, snook employ an ambush strategy of predation (waiting in the shadows of the mangroves for unsuspecting prey to pass by) throughout their range.  So a fly angler hoping to latch onto a large snook will do well by casting a streamer into the shadows and prop-roots along a mangrove-lined shoreline whether in south Florida or northern Mexico.

However, there are also many differences between regions - some of them subtle, some more obvious - that an observant angler will note and incorporate into a fishing strategy.  These differences range from the way in which apparently similar habitats function to the behavior of some of the species of gamefish that range across different environments.  Again, I will use snook as an example: in south and 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).  Seasonal differences in Central America, the center of the snook's range, are minimal in comparison and so are the snook's behavioral changes.

In contrast to the moderate temperature range in the tropics, water temperatures in subtropical areas can vary considerably between summer highs and winter lows, though not as much as in warm-temperate latitudes.  There can even be some abrupt and drastic changes in water temperature within a season B particularly in winter when a cold front causes water temperatures to drop so quickly that fish may die of cold shock.  This seasonal variation, and the region=s maximum and minimum temperatures, are key factors in structuring the habitats and fish communities in this region.

Cold-Blooded Fish
Since fish are cold-blooded, temperature is a controlling factor in their distribution. This is why you will not regularly find snook very far 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, slower to eat and flee from predators, and certainly more reluctant to take even the best fly.  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 59 degrees F can be problematic.  Juvenile snook are not as tolerant of cold temperatures, having trouble when the temperature approaches 52 degrees F.  Snook generally don't spawn until the water temperature approaches 78 degrees F, so temperatures between 75 - 85 degrees 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 a 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 – for fish that undergo seasonal migrations, the first cold front of fall often spurs them to put on the feed bag.

Red drum have a wide temperature range in which they will be active, from 50oF to the mid-80s, but seem to prefer water from the upper 50s to upper 60s. The behavior or red drum 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 50s, 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, the sun will warm the flats considerably, especially if there is a mid-morning low tide.  A flat covered by water that is 55 degrees F in the morning can warm to 58 - 60 degrees by early afternoon, and coupled with an incoming tide, can stimulate a period of feeding by red drum.  Even though they may be rooting in the bottom for crabs and shrimp, these drum will probably not be the most energetic, so may be slow to see and pursue a fly.  Your approach to these fish should take this into account - the crab and shrimp flies should be cast very close to the fish and any movement of the fly should be slow.  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.

Since water temperature in the subtropics varies from tropical highs to temperate lows, the array of fish you will encounter will be a mixture of tropical and temperate species.  For example, in the Florida Bay region of south Florida you might find both bonefish and red drum.  And each summer, juvenile bonefish are found in shallow seagrass beds along the west Florida coast, the result of larvae that rode currents up the coast from spawning areas farther south.  But these juvenile bonefish perish when the water cools in the fall, so there are no adult populations in these areas.  In contrast, red drum thrive in the subtropical environment of Florida and north into the warm-temperate region, but are generally not found farther south.  Some species, such as tarpon, are found throughout the tropics year-round, and in the subtropics and warm-temperate regions in the warmer months.  

Fish that stick around an area throughout the year are forced to search out locations that provide the required temperatures in each season.  For snook in the subtropical latitudes, this means a winter migration from their summer haunts in estuaries and along coasts 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 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 on a bit of a feeding, which can make for some great fishing.  A favorite spot for me at times like this is a mangrove shoreline and flat that lie next to the mouth of a deep tidal creek.  Snook that were sulking in the deeper parts of the creek during the previous cold spell can be found sunning themselves on the flat.  Small shrimp and baitfish patterns are good bets in these conditions.

Although snook may be active throughout the year, where they feed, their rates of feeding, what they feed on, and their attitude toward a fly will vary with water temperature.  For example, during the summer and fall months, pinfish (Lagodon rhomboides) is high on the snook menu in Charlotte Harbor, but during winter snook stomachs hold few pinfish.  You should take this seasonality into account when selecting a fly pattern for your next snook fishing adventure. 

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.  During the migration, tarpon may encounter habitats that are somewhat different - coral reefs and seagrass beds in the south and mangrove-lined estuaries or temperate marsh in the north.  Some of these areas will have clear water, in other areas the water will be murk, with sediments churned by waves, or perhaps the water will be stained brown by the tannins from mangroves lining the rivers and estuaries.  Thus, 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.  Each scenario changes the degree to which tarpon rely on different senses.  In clear water, a tarpon has to be able to see the prey yet get close enough to capture the 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 - patterns tied to pique the tarpon's interest in clear water might be colorful attractors, suggestive mimics, or exact copies of a natural prey item.  In contrast, flies used in murky or tannin stained waters need to attract a tarpon to within striking distance by the fly's movement, but then must be discernable as prey once the tarpon is within striking distance.

Overlaying the seasonality described above - migrations, changes in energy level and behavior - is the seasonality due to life cycles of gamefish and their prey.  This was addressed in Part 1 of this series, but deserves mention again.  Each species has a time of year and temperature that is the best time to spawn.  The fish (or shrimp, crab, etc) must have enough energy stores to spawn; the water temperature, salinity, and oxygen must be at the right levels; and when the larvae settle onto the bottom to begin life as juveniles, they must have access to sufficient food and shelter to be successful.  All of these variables depend on season, and result in a constant rotation in predator and prey interactions.  For example, late summer and fall are good times to find juvenile blue crabs in the grass beds of southern Florida.  Juvenile flounders are also found in the shallows during summer and fall, and are on the menu of red drum cruising grass and mud flats this time of year.  A Chernobyl Crab, trimmed flat and with abundant marabou in the wing, makes a workable imitation of a small flatfish.

In addition to affecting the type and abundance of prey during the year, the life cycle also influences the location and abundance of gamefish.  Spawning behavior is an example.  Some species gather in large groups to spawn en masse (called a spawning aggregation), which seems to have been a successful approach (many species of marine fish employ this strategy).  In Florida, snook spawn in aggregations during late afternoon into evening in passes and inlets during the summer and early fall.  Individual fish probably spawn every few days, and will often take a breather and feed along nearby beaches in between spawning days.  Knowledgeable anglers will adjust their schedules accordingly, and will spend many dawns searching for large snook along beaches near inlets and passes.  Deceivers of 3" that match the members of the herring family (Clupeidae) that are found along the beaches this time of year are the best bets.

Finally, perhaps because species that live in subtropical and temperate environments have ranges that extend over wide areas, there can be considerable differences in how a single species uses habitats.  For example, most of the red drum in estuaries of southwest Florida are juveniles and young adults.  These are the fish we most often see tailing on the flats.  Adult red drum are mostly found in offshore waters where they are out of reach of a fly rod.  In contrast, it seems that red drum in Mosquito Lagoon, on Florida=s east coast, remain in the lagoon into adulthood, and spawn successfully within the lagoon.  Not only that, but red drum on Florida=s east coast generally grow larger than their brethren on the west coast. 

Conservation
With the population increasing along our coasts at a rapid pace, the stresses on our coastal resources are also increasing.  Problems associated with this growing population are numerous, and increasing angling effort is one of them.  Since there are more anglers chasing the same number or fewer fish, we have to take special precautions in how we act while on the water.  One way we can make a difference is to be especially thoughtful when we are deliberating whether or not to keep a fish.  This is especially true for species that use the estuaries (where so much of the population increase is occurring) as nursery grounds for juveniles.  For such species, a fish or two on occasion is fine, but a couple a day for many days is probably overdoing it.                

Sidebar 1:  Although prey species will be different in many of these areas, they are similar enough in appearance that a single fly pattern can be used.  For example, the small green reef crab is a common prey item of permit in tropics, and is imitated by numerous fly patterns.  In south Florida, the mud crab is a common prey item of red drum, so imitations of mud crabs are good flies for red drum feeding on the flats.  Fortunately, the green reef crab and the common mud crab are very similar in size and color, so the same fly patterns should work well for both permit and red drum.

Sidebar 2: There is also a seasonality in the tides.  In winter, the average tide level is lower than during the summer.  You can use this information when deciding what areas to fish and what flies to use.  During the winter low tides, seagrass beds that were waist-deep during summer will be shallow enough for wading and sight-fishing. These grass beds will likely harbor numerous species of shrimp (grass shrimp, snapping shrimp, juvenile pink shrimp), juvenile blue crabs, mud crabs, hermit crabs, juvenile flounder, and an assortment of other prey.  In summer, when these areas might not be appropriate for wading and sight-fishing because of the higher average tide level, you might search for shorelines with populations of fiddler crabs.  As the high tide inundates these fiddler crab colonies, gamefish may prowl these areas in search of a meal, or a dropping tide may wash a few crabs into deeper water.

Sidebar 3: Seasons also influence what gamefish eat, so you should be prepared to adjust your fly selection accordingly.  For example, pinfish are a major diet item of snook in summer, but the average size of pinfish varies during the year.  In spring, juvenile pinfish an inch or so long are abundant in the grass beds, but by fall these fish have grown considerably.  What's more, you may find that the pinfish are different sizes in different locations.  A selection of high-bodied, white and yellow flies, from 1" to 4" or so should cover the range of pinfish sizes you are most likely to encounter. 

Gamefish will also change the dominant prey in their diet on a seasonal basis, so you should be ready to try a number of different patterns with each season.  For example, speckled trout will change preference between shrimp and fish, depending on the season and their location, and knowledge of your local area will be paramount to knowing when they prefer what prey.

Sidebar 4: When wading in the subtropics - whether along the outer beaches or in an estuary - you must be especially vigilant for stingrays.  Stingrays will often lie partially buried in the sediment, and can be almost impossible to see - especially when the water is murky.  Usually a stingray will move as you approach, but not always, so you should shuffle your feet when wading.  Stingrays have a large spine at the base of their tail that they can whip up into your leg if stepped on, inflicting a painful and potentially dangerous wound that will end your fishing for a while.