Modifying mosquito impoundment management to enhance nursery habitat value for juvenile common Snook (Centropomus undecimalis) and Atlantic tarpon (Megalops atlanticus)

Abstract

Coastal wetlands function as nurseries for juveniles of many fishes, including common snook (Centropomus undecimalis) and Atlantic tarpon (Megalops atlanticus). Thousands of hectares of mangrove habitat in the Indian River Lagoon (IRL), Florida (USA) have been impounded for mosquito control, limiting connectivity and potentially decreasing nursery habitat value. Many impoundments are managed to provide connectivity through culverts to the IRL from October through April (non-breeding season for mosquitos), with the impoundments isolated and filled with water to control mosquito breeding from May through September. To determine whether seasonality of impoundment-estuary connectivity affected nursery habitat value, we conducted a quantitative assessment of the emigration of juvenile snook and tarpon from Bee Gum Point, a mosquito impoundment in the IRL. A total of 305 snook and 103 tarpon were captured within the impoundment and marked with passive integrated transponder (PIT) tags. Pairs of tag-detecting antennas were established at culverts in two basins within the impoundment and monitored for 2 years. Only four tagged snook, and no tagged tarpon, were physically recaptured, while nearly 71% of the tagged snook and 77% of the tagged tarpon were detected at least once by antennas on the inside of the impoundment. Antennas on the outside of the culverts detected only 18 snook and eight tarpon emigrating through the culverts during 418 days of two open seasons. When culverts were experimentally opened for a total of 21 days in three periods during two summers, both snook (n = 49) and tarpon (n = 22) emigrated at far higher rates that they did during the normal open season. This significant increase in emigration indicates the importance of managing habitat connectivity to correspond to natural seasonal emigration patterns to increase the productivity of these fish nurseries.