How telemetry tag data could improve the odds of redfish and trout reaching trophy size
Ashley Ferguson may not be a fish surgeon, but she’s become pretty handy with a scalpel and sutures over the last four years. Ferguson is one of a half-dozen fisheries biologists with the Louisiana Department of Wildlife and Fisheries who implant telemetry tags in redfish, speckled trout, sharks, and—hopefully—tarpon in the Lake Pontchartrain Basin.
Each tag sends a unique signal in the form of a “ping” to a series of yellow buoys anchored in strategic locations throughout Louisiana’s largest brackish-water lake. Analysis of data from the buoys is helping biologists better understand how fish use different types of habitat and react to changes in temperature, forage, and salinity.
“We have a buoy on every artificial reef, on each of the major bridges, and in the passes leading into and out of the lake,” says Ferguson. “If one of our tagged fish swims within 500 yards of a buoy, we can download the information and establish a pattern of where those fish are moving—and why.”
The study was launched in 2012 as a cooperative effort between Louisiana State University and the department, but it has been run by Wildlife and Fisheries in the last two years, thanks to grants from the angler-driven Sport Fish Restoration Fund.
Avid Lake Pontchartrain anglers are in on the project in a hands-on way, as well. For three to four days each year, anglers aim to catch trout that are longer than 18 inches and redfish that are longer than 21 inches and keep them in their live wells for the journey to the Percy Viosca, Jr., a converted aging shrimp boat where fish are held in oxygenated tanks.
That’s where Ferguson and her team get to work cutting and stitching.
Once a telemetry beacon is inserted, the fish’s backs are marked with a light blue tag to help anglers recognize them as part of the study so they can be released. From the launch of the project through the end of 2015, the team tagged 244 trout, 64 redfish and 18 bull sharks.
On a rare windless day in early January, I joined biologists and a handful of anglers on Lake Pontchartrain to add to the trout and redfish totals. Gulls diving on hand-sized white shrimp pointed to the location of huge schools of trout and redfish along the south shore. By noon, more than 20 new tags were pinging silently from stomach cavities.
Biologists were particularly interested in capitalizing on the ideal fishing weather because of the changes coming to Lake Pontchartrain this winter and spring. Just 48 hours after the fish were tagged, the Army Corps of Engineers opened the Bonnet Carre Spillway, a relief valve that directs sediment-laden flood waters from the Mississippi River into the lake when river levels threaten to overtop levees in New Orleans. Bonnet Carre’s gates only open about once a decade, but this year’s opening comes just five years after record flooding that forced the opening of spillways throughout the Mississippi River Basin.
“This year is the first time since we started the study when we’ve had a spillway opening, and we want to see where the fish go, if they leave, and how long it takes them to come back,” says biologist and fish tagger Craig Gothreaux. “Usually, a spillway opening causes a temporary displacement, and the saltwater fish return when salinities come back up a couple of months after the gates are closed. But, do the redfish behave differently than the trout? Does opening the spillway this early in the year have an effect because the water is colder? Hopefully we can figure that out by looking at what we get from the tags.”
What biologists have figured out, spillway open or not, is that many of the area’s renowned trophy trout leave the lake in early June to spawn in the saltier adjacent waters of Mississippi Sound and Breton Sound. Buoys in the passes leading to and from the lake light up again in early fall as trout return to feast on annual crops of white shrimp and menhaden—which get even larger after a spillway opening.
“If they leave the lake or just stay here and find the pockets of salty water, we’ll be able to read the buoy data and know,” Ferguson says. “Even if they go to Mississippi or Alabama by chance, we’ll know because researchers there use the same equipment and each tag sends a unique signal.”
Ferguson adds that the data shared among Gulf States is helping track other species, like the endangered Gulf Sturgeon, and will allow for an expansion of tagging efforts across the region on fish like red snapper, grouper, and even highly-migratory king mackerel and tuna.
The TRCP and its conservation partners have recommended expanding on projects like Louisiana’s telemetry tagging effort, which will be essential to the long-term monitoring of fish stocks in the wake of the 2010 oil spill. The data collected will help biologists establish baseline information vital to understanding how future disasters and weather events affect fisheries. The tagging efforts also give anglers an opportunity to be more involved in helping scientists gather important information—consider it a normal day of fishing with a little biology lab thrown in.
Want a peek at the travel routes of these fish? Click here.
To learn more about the TRCP’s work in the Gulf of Mexico and beyond, visit our website: trcp.org