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Sea School students discover where the water goes

By Staff | Aug 30, 2011

Sanibel Sea School student Kyle Hasenfus paints up a coconut prior to the release.

The very last week of the summer at Sanibel Sea School’s summer camp was Tarpon Week and what better way to celebrate a summer of fun and learning than to pay homage to the Silver King. We made otoliths the ear bones in fishes, used by biologists to age them. We canoed through the backwaters of mangrove forests in Tarpon Bay where tarpon thrive as young fish. But the really interesting stuff started happening when we studied how adult tarpon spawn and how the larvae of these mighty giants are, to some degree, at the mercy of the currents.

In conjunction with that knowledge of larval dispersal we asked a tantalizing question. Just where do the currents take tarpon eggs and larvae if they spawned off the shores of Sanibel? To answer that question of current movements, we decided to use coconuts to try to track water movements off the shores of Sanibel Island. We chose coconuts because they are a natural part of the flotsam of the Gulf of Mexico and besides, who wouldn’t love to find a message on a coconut?

So, we gathered up 30 coconuts and painted them crazy colors mostly pink and orange. We wanted our coconuts to attract folks on distant shores to come and have a look wouldn’t you look if you saw a pink and orange coconut in the shallows off the beach? We painted numbers on each one and affixed laminated tags asking the finder to call or email Sanibel Sea School when they found our wayward coconut.

On Thursday at 11:15 a.m., we took the boat to point just offshore of the Sundial Resort, which is a favorite hunting ground for tarpon fishermen and we set our groups of coconuts adrift. We anchored the boat and observed the direction we saw the coconuts moving they all seemed headed to Captiva. We eventually weighed anchor and traveled further up island.

We enjoyed a picnic lunch and seined for near-shore fishes always in search of those elusive tarpon larvae. We then got back in the boat and sampled the plankton with a plankton net a fine meshed net designed to capture creatures greater than 0.3 mm in size.

Two coconuts ready to be deployed on their epic journey.

Once our plankton observation was done, we headed back to our deployment point to hopefully visit our coconut current drogues. But, we could not find a single coconut on the Gulf of Mexico it was as though a giant wand had erased our happy little coconuts from the earth. Oh well, we would just have to wait and see if anyone would find our little friends and give us a call.

The first message arrived at Sanibel Sea School on Friday evening. Someone had found one of our coconuts in Naples! Our initial prediction of Captiva landings, based on the observations of the drifting coconuts, didn’t pan out. Over the weekend, 18 more were reported from kind people who found coconuts all over the beaches of Naples and even on Keewaydin Island, south of Naples. We still have calls coming in and great hopes for the rest of our coconut explorers. Next stop? Maybe Marco Island? Maybe Cuba?

Our coconut current study is yielding a lot of insights. One of them is that what we do here on Sanibel can have a direct impact on our neighbors on Naples it’s funny, I never thought of Naples as the town next door, but in our ocean world they seem to be. And that makes us wonder about the flotsam landing on our beaches. Where is it coming from?

We learned a lot in our last week of summer camp. We celebrated the Silver King, made new friends, had some adventures and found out that pretty interesting things can happen when you study the ocean in simple, old-fashioned ways.

Sanibel Sea School is a 501c3 dedicated to a world in which all people value, understand and care for the ocean. Visit us in person or at “http://www.sanibelseaschool.org”>www.sanibelseaschool.org.