TARPON BEGIN their lives looking like a clear worm. Adult tarpon spawn offshore: 80 to 100 miles in the Gulf of Mexico and 5 to 10 miles in the Atlantic Ocean. Once eggs fertilize and hatch, tarpon begin their larval stage looking like a transparent flat ribbon. This particular larva, similar to eels, bonefish, and ladyfish, is known as a leptocephalus. Although leptocephali do have the ability to swim, they are mostly drifting with currents to make their way back inshore. A study on the Indian River Lagoon found that tarpon larvae enter the passes at night and make their way into far reaches of the estuary to find calm, tidal backwaters where they metamorphose into juveniles.
They can breathe air. Although we can’t exactly compare juvenile tarpon to Flipper, tarpon have a unique capability of taking oxygen from above the surface instead of relying on dissolved oxygen in the water. Tarpon have a modified swim bladder that has rows of vascularized (i.e. spongy) tissue that can act as an extra set of gills. In contrast, other fish typically have a balloon-like swim bladder that can only help with buoyancy during pressure changes.
Gulping air is a major benefit to juvenile tarpon who seem to prefer habitats with low dissolved oxygen that exclude other fish that could be competition or predators.
They eat anything and everything. Another good strategy for juvenile tarpon in backwater habitats is that they are opportunistic feeders. A study on the east coast of Florida looked at the diets of juvenile tarpon compared with prey availability for seven locations and concluded that tarpon eat everything. The only limiting factor was whether the food would fit in their mouth. Therefore, the larger the juvenile tarpon grows, the more things it could eat. Fish and copepods are the main organisms consumed, but tarpon also eat ants, crabs, shrimp and fly larvae.
Their growth rates depend on habitat quality. Although the scientific literature is limited on juvenile tarpon studies, some show tarpon in captivity and natural habitats exhibit growth rates of 10 to 12 inches per year. Likewise, the Florida Fish and Wildlife Conservation Commission (FWC) found comparable growth rates of juvenile snook (who use similar habitats) in the Tampa Bay estuary. However, BTT studies in southwest Florida and coastal South Carolina of juvenile tarpon in human degraded habitats found average growth rates of 1-2 inches per year. These studies underscore how detrimental coastal development; altered waterflows and nutrient runoff are to our fisheries.
About two thirds of angler-reported juvenile tarpon habitats are degraded by humans. In 2016, BTT started a juvenile tarpon habitat mapping project to find locations of tarpon 12 inches and smaller. Anglers reported almost 300 locations and were asked to describe the site as natural or altered. About 64 percent of reported sites were described as having some level of degradation. Couple this information with slow growth data in human-impacted sites, and it’s clear just how important habitat protection and restoration are. For more information visit bonefishtarpontrust.org.