Red Tide is one of those phrases that people talk about but don’t really understand. Like New Labour, Quantitative Easing, plausible deniability and El Nino. We know they mean something significant but aren’t exactly certain what.
Last week we were fishing off the coast of southern Belize in the Caribbean for the large Tarpon migration which happens during the months of July, August and September. The Tarpon follow the great shoals of bait fish that annually move through this area; minnows and small sardine-like fish in large masses. While there are resident Tarpon around the many mangrove lagoons, the biggest in size are the migratory Tarpon. We were well equipped, eager and ready for the challenge of hooking and landing the “silver king”.
But this year was not normal. It seems that several weeks before our arrival in southern Belize there was a prolonged Red Tide that either killed or drove the bait fish schools out into the open water, away from the Tarpon migration route. So, all we saw for the week were a few resident fish rolling or jumping and managed to only hook, and lose, one fish all week.
So what is this Red Tide menace? As a curious fellow, like most fly anglers, I wanted to know more so I dug deep into my marine biology background and researched the internet extensively to understand this infrequent yet deadly phenomenon.
In a nutshell, here’s what I found out about Red Tide
At the base of the food chain are microscopic single-celled algae, or dinoflagellates, which comprise a large part of the energy-producing plankton found in the sea. Occasionally, algae can grow fast or “bloom” which results in dense and visible patches of varying color in the water. When an upwelling occurs in the ocean, bathing the surface plankton in nutrients from the bottom of the ocean, or land runoff rich in fertilizer and other nutrients flows into the estuaries, they trigger an algal phytoplankton ‘bloom”. Their population density may reach several million per liter of water.
These ‘blooms’ are a population explosion and may cause discoloration of the water golden or red, and is called ‘red tide’ (due to accumulation of carotenoid pigments). Most algal species are not harmful, but there are a few species that produce poisonous toxins.
The ensuing “red tides” can have harmful effects on the sea life in and among coral reefs and mangrove habitats, where the bait fish for the Tarpon congregate.
Red tides can become a problem because of their domino effect in the food chain. When these tiny plants undergo an algal bloom, they are consumed in enormous quantities by plankton eating shellfish, small fish fry and schools of bait fish.
It’s almost impossible to predict where and when a red tide event will take place, but most occur along the coastal areas in association with upwelling currents, changes in current patterns, or excessive rainwater runoff from nutrient rich farming areas. The most common sites are along the Florida coast, the Gulf of Mexico, and along the Mexican coast. In Florida, red tides usually occur in late summer and fall, but they’ve also occurred in just about every month. During an event, fish affected by the neurotoxin become paralyzed and stop breathing, eventually washing up on the beach.
My hunch is that the large schools of bait fish and “glass minnows” that the Tarpon feed on are negatively affected by this toxic algal bloom, some dying but most of the schools driven to offshore areas of cleaner water. Some scientists believe the mass of algal cells clog the gills of small fish affecting their oxygen intake.
So, during our Belize fishing holiday it seems that the big migratory Tarpon followed the retreating bait fish out beyond the barrier reef and were nowhere to be seen in the mangrove lagoons that they tend to frequent, crashing into schools of bait fish and feeding voraciously. In fact during the entire week we only saw one rolling tarpon in a region that is normally full of fish.
A suggestion to saltwater anglers
If who have booked a lodge or guided fishing trip for Tarpon, first, buy trip cancellation insurance and make certain it includes weather related events. Second, keep in close contact with the lodge for several months in the run up to your scheduled trip and ask about catches, anomalies, and particularly Red Tide. You might save yourself a disappointing trip.
Fishing is never disappointing, but the catching may suck!
Tight Lines . . .
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