ICHTHYOPLANKTON RECRUITMENT WITHIN MANGROVE-DOMINATED MOSQUITO CONTROL IMPOUNDMENTS

Coastal wetlands across the Indian River Lagoon (IRL) on the east coast of Florida have been impounded for mosquito control purposes, which have been known to have adverse effects on overall fish populations. The objective of this project was to assess the use of culverts by species of larval fish at three impounded mangrove sites in the IRL. Light traps were used to collect samples of larval fish (both inside the basins and in the surrounding lagoon) which were humanely euthanized, preserved, and examined under a digital microscope. A total of 3,926 fish were collected from 24 taxa in 576 samples over the year-long study. Larval seasonality generally followed known reproductive seasonality of the species captured. Inside the impoundments were dominated by species known to spawn in and around mangroves such as the Gambusia holbrooki and Poecilia latipinna. Species that spawn in the IRL or in coastal waters that subsequently use the IRL as a nursery (such as Anchoa mitchilli and Gobiosoma robustum) had relatively low catches in the impoundments. Larvae of the main sportfishery species that have juveniles known to utilize the studied impoundments (Megalops atlanticus, the Atlantic tarpon, and Centropomus undecimalis, the common snook), were rarely caught inside the impoundments or in the surrounding IRL. The low numbers of IRL and offshore spawning larvae that enter the impoundments may be hindered by restricted water flow through culverts connecting the habitats, or by their inability to survive the low DO conditions often found inside the impoundments, especially during the summer. The lack of larval tarpon and snook in the light collections suggest that these species metamorphose from the larval to juvenile stage outside of the impoundments, before they enter the mangrove-dominated nursery habitats. The results of the study can be used to further modify impoundment restoration and management strategies to enhance their role as fish nursery habitats.