While most people look at Fort Myers Beach and see a beachfront vacation mecca, the island's economy also relies on a large shrimp fleet that uses it as a home base.

To get a glimpse of that side of San Carlos Island, take a free, self-guided walking tour that reveals much about its ecology and history.

Pick up a brochure at the Fort Myers Beach Welcome Center, 17200 San Carlos Blvd., or at the Ostego Bay Foundation Marine Science Center, 718 Fisherman's Wharf.

The marine science center, situated along the trail, is a good place to start the half-mile tour. Get an up-close look at remnants of old shipwrecks, find out about mangroves and the vital role they play in preserving the island, and see some live sea horses and other marine creatures.

From there, follow the trail to the five points at which kiosks have been set up. Each one contains narrative and pictures that explain such topics as how to discern a snapper from a snook and how flocks of pelicans faithfully follow well-laden shrimp boats to the docks in search of an easy meal.

The trail leads walkers past establishments often overlooked by visitors: shrimp docks, seafood packers, and markets selling super-fresh seafood.

Get a taste of the place by stopping for lunch at the Beach Seafood Market, where the informal dining area looks in on a huge machine that sorts shrimp by size before they are packed into big boxes and sold wholesale.

The Ostego Bay Foundation gives a guided tour of the trail beginning at 9 a.m. every Wednesday. Be sure to call ahead to reserve a spot.

The Ostego Bay Foundation is open from 10 am. to 4 p.m. Wednesday through Friday and 10 a.m. to 1 p.m. Saturday. A $10 donation is suggested for the guided tour. For details, call the foundation at 765-8101.