A Lagoon is by nature a very shallow body of water. The Indian River Lagoon has an average depth of only 2 1/2 feet. Many of the mangrove islands were formed in the 1920's when the Army Corps of Engineers first dredged the ICW to allow safe inland navigation for large vessels. Vero Beach and the Indian River Lagoon is also the home of the famous Harbor Branch Oceanographic Institute.
Using giant dredges they would suck the bottom soil from middle of the lagoon and simply deposit it to either side. Eventually these deposits would sprout life in the form of mangrove seedlings, Autrailian Pine trees, and assorted types of palm, and palmetto shrubs. In time it has produced a beautiful and scenic ecosystem.
Mature coastal fish like the snook, redfish, sea trout, tarpon, various types of sharks, barracuda, and jack cravalle migrate into the lagoon after spawning to deposit their eggs or to simply feed. It's in this lagoon that many fish will spend the first 3 to four years of life before reaching maturity, thus replacing the previous stock, and then it all happens over, and over again. As you may suspect these predatory fish aren't the only ones to take advantage of the estuary.
The prey fish use this ecosystem as well, mullet, threadfin herring, grunts, croakers, pinfish, glass minnows as well as shrimp and assorted crabs. The current estimate is that more than 4,300 types of fish and animals utilize the lagoon at one time or another over the course of their lives. Bottle nose dolphin, manatees and otters are just a few of the mammals that also share this very bountiful universe.
Let's also not forget the additional life above the water line. The sea birds; Pelicans, gulls, the fish eating cormorants, Herons, Ibis,' mammals like; Raccoons, Squirrels, Opossums, Bobcats, reptiles such as; Green and Brown Anole lizards, Snakes like the Black Racer, the Banded Water Snake, along with numerous toads and insects even alligators.
Mix all this together and what you get is a macrocosm for all types of wildlife. Plenty of food for the smaller prey fish to eat around the mangroves, crabs, shrimp, and small minnows making up the majority of their diet. In turn while they're fattening up under the protection of the mangroves the predatory fish are feasting on them.
The lagoon system is a unique environment a constant migration of life, and naturally death. Now granted this is not a very scientific explanation but I'm not a scientist I'm a fisherman, and all I know is that it's beautiful system that nature has devised. The only natural enemy threatening it are humans.
