Summers in Southwest Florida are known for plenty of sun and plenty of heat. But to me, the hallmark of the season is really thunder. Daily or near-daily storms pour trillions of gallons of water onto the land, and a significant portion of that water ends up in our estuaries. The main effects there are lower salt content and darker water due to tannins from decaying plant matter.
Like all things, the summer rains have to come to an end. In most years, that happens more or less approximately in about the last half of September (ish). This year, a near-miss from an extraordinarily powerful hurricane and swipes from a couple more tropical cyclones seem to have put the kibosh on our rainy season a bit early. Hurricanes dump a lot of rain quickly, but they tend to leave dry air in their wakes.
One thing that dry air does is it allows our nighttime temperatures to drop a bit. It’s still plenty hot during the day, but cooler air at night means that some of the heat in our shallow waters can dissipate. A drop of only a couple degrees is enough to get our flats fishing fired up. During these times, the bite will usually be peaking in the early mornings.
Eventually that lower humidity will be part of the reason our daytime temperatures will be more comfortable as well. For all the talk about carbon dioxide and methane as greenhouse gasses, water vapor has a much greater effect on day-to-day temperature changes.
An obvious effect of less rain is less runoff flowing from the rivers and into the Harbor. When less water is coming down the rivers, the estuary is more strongly influenced by the salty Gulf of Mexico. Every incoming tide pushes high-salinity water up into the Harbor. By the time we reach minimal river flows in spring, the water will be close to sea-strength salty all the way up into the river mouths.
Rising salinity affects different species in different ways. Most of our estuarine fish can tolerate huge variations in salt content, but changes can act as sort of an alarm clock. Take snook as an example. When salinity starts rising in the fall, that’s a cue to move from the beaches and passes into backwaters and the rivers. Even though the water still looks brown, they know that it’s saltier than it used to be.
Other fish need high salinity. Mackerel are a good example. When there’s a lot of runoff and the Harbor’s water has little salt content, they rarely venture inside even if there’s plenty to eat. But now, as the salinity is rising, we’re seeing lots of Spanish mackerel in the lower Harbor.
Fresh water outflows extend out into the Gulf as well. Fish that insist on water that’s close to sea-salty often stay many miles out from shore at those times. Now that the outgoing tides don’t carry as much fresh water out, pelagic predators such as kingfish and little tunny will be showing up much closer to shore.
There should be plenty for them to eat when they arrive. When the nutrients the rivers have been carrying downstream meet up with highly salty water, the result is an explosion of life at the very bottom of the food chain. Tiny planktonic plants and animals are food for baitfish, and I think you already know what eats baitfish. Rising salinity in fall means a bountiful buffet, and plenty of action for us anglers.
While it might not feel like fall, there are lots of changes happening right in front of us. If you want to improve your angling skills, you need to be paying attention to those changes. Many of them are subtle to us because we spend most of our time indoors and don’t live underwater. But for the fish, which are literally immersed in their environment, these seemingly insignificant changes are huge. You would do well to be aware of them.
Robert Lugiewicz is the manager of Fishin’ Frank’s Bait & Tackle, located at 4425-D Tamiami Trail in Charlotte Harbor. Call 941-625-3888 for more information about the shop or for local fishing info, or visit them online at FishinFranks.com.