Juvenile tarpon Megalops atlanticus use of natural and managed marsh habitats in coastal South Carolina

There is a paucity of information on juvenile tarpon Megalops atlanticus habitat use at the northern edge of its distribution. Therefore, we investigated the timing of recruitment and the size distribution of juvenile tarpon in natural and managed marshes in coastal South Carolina. We monitored recruitment to salt marsh habitats during July through November 2019 in the North Inlet estuary, Kiawah Island, and Tom Yawkey Wildlife Center Heritage Preserve. One-hundred and two juvenile tarpon (36-333 mm standard length) were observed during July to November. Tarpon from natural marsh pools (North Inlet estuary; mean +/- SD = 65.4 +/- 20.2 mm) were smaller than those from managed impoundments (Kiawah Island and Yawkey Preserve; 253.9 +/- 41.6 mm), with no overlap in size across habitats throughout the study duration. Mean tarpon length was relatively constant throughout the study in marsh pools (65 +/- 20.2 mm SL), but mean tarpon length increased from 180 +/- 9.9 mm SL in August to 290 +/- 31.5 mm SL in October in managed impoundments. Peak catch-per-unit-effort occurred during August (marsh pools) into September (managed impoundments) across habitat types and declined as water temperatures decreased at the end of October to November. The absence of size overlap between habitats and increasing size of tarpon over time in marsh impoundments compared to the minimal change in length over time observed for marsh pools suggests that (1) tarpon are transient in marsh pools early in life, (2) tarpon do not enter impoundments until reaching a certain size, (3) small juvenile tarpon are cryptic in impoundments and larger juvenile tarpon are more susceptible to capture in those habitats, or (4) a combination of (1), (2), and (3).