SEASONALLY MANAGED CONNECTIVITY OF AN EAST FLORIDA MOSQUITO IMPOUNDMENT TO INCREASE EMIGRATION OF JUVENILE SNOOK AND TARPON FROM THE NURSERY HABITAT
Cianciotto, Anthony Carl
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Mangrove marshes are nursery habitats for juveniles of many fishes, including snook (Centropomus undecimalis) and tarpon (Megalops atlanticus), which are important recreational fisheries species in Florida. Thousands of acres of mangrove marshland in the Indian River Lagoon (IRL) have been impounded for mosquito control. Most of these impoundments are under Rotational Impoundment Management (RIM), in which culverts connecting to the IRL are closed in the summer to control mosquito reproduction, and opened Oct-May to allow water exchange. We conducted a quantitative assessment of the emigration of juvenile snook and tarpon from the Bee Gum Point Nature Preserve impoundment in Vero Beach, Florida. During 9 months of tagging, 284 snook and 70 tarpon were marked with passive integrated transponder (PIT) tags and released back into the impoundment. Tag-detecting antennas around the culverts recorded minimal emigration when the culverts were open according to RIM in winter. Tagged juveniles remained trapped after the culverts were closed for the summer, but approached the antenna frequently. We therefore conducted an experimental summer drawdown, opening culverts to allow free water flow for 2 weeks in July. High rates of emigration were recorded for both juvenile snook and tarpon during the first two days of the drawdown. A total of 9.5% of the tagged snook and 17% of tagged tarpon emigrated from one site during the 2 week summer drawdown. This indicates that juvenile snook and tarpon are more likely to emigrate from impoundments during summer, when culverts are typically closed. The results suggest that impoundment management may be enhanced by including short term openings of culverts in summer to allow juveniles to emigrate, improving their value as nursery habitats.