Estuary Nurseries: Early life histories of popular sportfish
Perhaps the most well-known function of estuaries, such as Charlotte Harbor, is their role as nursery grounds for growing fish, shrimp and shellfish. Very few marine species spawn in estuaries, but estuaries are used extensively as nursery grounds. Most fish and crustaceans (crabs, shrimp, etc.) spawn offshore. The eggs are typically planktonic (free floating). Eggs develop into larvae that depend upon tides and currents to transport them to suitable habitats to settle out and grow within. Settling young fish and crustaceans utilize a number of different survival strategies, but common to all is a quest to not be eaten.
As fish increase in size, habitat and diet demands largely determine where it will be found. How and for how long fish utilize the estuary varies by species. Gag will only spend about a year in the estuary before moving offshore. Redfish stay in the estuary for several years. Snook go offshore to spawn but then come back to the estuary and spotted sea trout live their entire life in the estuary. The innate need to reproduce, to ensure survival of the species, also determines where and when different fish species are found. Tides, day length, the lunar cycle, temperature and salinity all influence the fish spawning patterns.
Adapted from “An Abbreviated Look at Common Charlotte Harbor Fish Life Histories“, published Sept. 24, 2012. Also published in WaterLife Magazine, October 2012.