Ecological Studies

The St. Lucie County Mosquito Control District funded a study by the Marine Resources Council of East Florida, entitled "Sportfish Utilization of an Indian River Lagoon Seagrass Flat Adjacent to Managed Mosquito Control Impoundments." One part of this project was monitoring the spawning of spotted seatrout near impoundments 14A and 14B with a portable hydrophone that recorded sounds made by male fish to attract females. Biweekly (near new and full moons) surveys, between sunset and midnight, were conducted during the primary spawning season of May-September. The monitoring boat stopped at each sampling station (an Intracoastal Waterway channel marker or other known location), and the hydrophone was submerged to a depth of 1 meter where it recorded for 3-5 minutes, while sound was monitored with headphones. The recordings later were interpreted with sound analysis software and/or a graphic equalizer to filter the higher frequencies and allow good estimation of calling group size. Large numbers of calls were recorded in the survey area, confirming that it is regionally important for spawning.  The data were collected by Brian Barnett of Vero Beach, Florida.

Spectrogram of Calling Spotted Seatrout

*The above seatrout images are from the Fish and Wildlife Research Institute

Sheepshead Stocking

During 1984, 1000 hatchery-reared sheepshead (~3 inches) without tags were held in two cages in the perimeter ditch of the Fort Pierce Inlet State Park Impoundment (no. 18A) for several days (with close to 100% survival).  Then they were released into the ditch, from which they could enter the estuary.  There was no formal monitoring, but over the following weeks, some of the released fish were seen and were behaving normally. (funded by private donations)

Mullet Stocking and Tracking

During 1996-1997, 3332 hatchery-reared striped mullet (3-7 inches) with tags were stocked and monitored in impoundments at Round Island (no. 24) and Jack Island (no. 16A).  Their migration and other behaviors were very similar to those of wild mullet. (funded by a state grant and private donations)

Snook Stocking and Tracking

During 2002-2003, 156 hatchery-reared common snook (17-27 inches) with tags were stocked in impoundments at Bear Point (no. 1) and Wildcat Cove (no. 17A), then tracked inside and outside the impoundments. Three were seen, and four were caught (three by hook and line, one by seine) as far as 26 miles away from their release sites. All seven were in schools of wild snook of similar size and were reported to behave like and look as healthy as the wild snook. The three caught by recreational fishermen on hook-and-line were among wild snook being caught on the same baits: live mullet, live shrimp, and artificial shrimp. Nine of the 15 snook with ultrasonic transmitters were tracked within the impoundments (including one up to 361 days). Six with transmitters (making a total of ten tracked by that method) were located outside the impoundments up to 5 miles from the release sites. One of those was in an estuarine channel ~0.6 mile from the release site during 25-37 days, was detected at the mouth of a freshwater creek 3 miles away at 59 days, and was caught and released by a fisherman under a lighted dock in a finger canal 1.8 miles away at 349 days. Then, during 353-354 days, the same fish was monitored by a receiver and seen under the dock where it had been caught.  All tagged snook seen, caught, or located were in areas preferrred by wild snook. (funded by federal and county grants and private donations)