The number and variety of fish in the Florida Keys, coupled with our year-round inviting temperatures, make our islands a world-class fishing destination. Most fishermen naturally assume our southern latitude alone can control our temperature range, but in reality our islands are protected from harsh temperature swings by the moderating influence of the Gulf of Mexico Loop Current and the Florida Current.
As a result, the coldest it has ever been in Key West is 41 degrees and the hottest is 97 degrees. In addition, these warm ocean currents also serve to enhance the seasonal migration of a variety of coastal and pelagic game fish into our waters.
The currents moderating our island's ocean and air temperatures arise from strong westerly trade winds blowing above the equator. These winds set warm ocean waters in motion, driving massive amounts of water towards the Caribbean Sea. This moving mass of warm sea water is reinforced by the spin of the planet (Coriolis effect) which eventually directs the flow upward until it forms the Yucatan Current which ultimately flows deep into the Gulf of Mexico where this tremendous force gives rise to the Gulf of Mexico Loop Current.
The Gulf of Mexico Loop Current plays a vital role in the survival and distribution of fish, coral and crustaceans larvae throughout the waters of the Gulf of Mexico, as well as the Florida Keys. As the Loop Current pushes deep into the Gulf of Mexico, it creates a swirling clockwise flow pattern. This life sustaining current ultimately bathes the southwest Florida coast and the Everglades with nutrient rich waters loaded with chlorophyl and micro-zooplankton. This essential micro-food chain serves to support local as well as foreign spawned larvae (i.e., spiny lobster). The Loop Current eventually turns southward and pushes the nutrient and larvae saturated waters through the natural channels occurring between the islands of the Keys. This motion serves to distribute larvae throughout our back-country and ocean reef ecosystems and ultimately ensures the future of the next generation of gamefish.
For eons, fresh water flowing through the Everglades would mix with the saltwater Loop Current to create a unique brackish ecosystem which supported the life cycle of many of our gamefish (redfish, snook, sea trout, bonefish, and permit). Unfortunately, man decided to disrupt this fresh water flow and, as a result, we now see a decline in the sea grass ecosystems, as well as the remaining populations of these beautiful and economically valuable fish.
Once the Loop Current flows through the natural channels between the islands stretching from the Dry Tortugas to Key Largo, it gives rise to what oceanographers call the Florida Current. The Florida Current then flows forcefully offshore between the southern coast of the Florida Keys and the northern coast of Cuba. Fortunately, locally created large oval downward spiraling Ekman currents allow much of the larval populations to be pushed back over our reefs where they once again have the opportunity to be deposited in the reef ecosystem.
Seasonal temperatures, current flow rates and changes in salinity all impact the flow pattern of the Loop Current and sometimes create massive independent warm cut-off circular eddy(s) which spin off and travel northward. These now independent eddy(s) also carry larvae from billfish (particularly sailfish) all the way down to the smallest benthic larvae species allowing them to be further dispersed throughout the Gulf of Mexico waters.
The powerful Loop Current and its warm spin-off eddies have the ability to create a tremendous impact on the weather (i.e., rain and humidity) experienced throughout the southeastern U.S. and Florida Keys. In addition, this very warm ocean energy can enhance the rate of hurricane intensification/development as tropical cyclones form and/or move through the Gulf of Mexico.
Unfortunately, there is the potential for these vital massive global ocean currents to begin to slow down due to climate change. Changes in sea surface temperatures, air temperatures and glacial melting all have the ability to impact these currents' flow rates and salinity. Think of the Everglades freshwater effect... but on a worldwide scale. Negative changes in these global ocean currents will create havoc on worldwide fish ecology, especially when it comes to reproduction and mass species migrations. There are already signs some of these vital ocean currents are on the cusp of degrading.
Capt. Pete Peterson welcomes comments and suggestions sent to email@example.com.