Telemetry Tagging on Lake Pontchartrain
from The Fishing Wire

As part of an ongoing study of speckled trout, red drum and bull sharks in Lake Pontchartrain, the Louisiana Department of Wildlife and Fisheries will again host its annual fall acoustic telemetry tagging event during the week of November 16.

In the fall of 2012, the department launched the project to collect continuous data on individual movements of these species over time. The data collected provides insight to seasonal migration patterns, habitat use and how movements may vary between sexes.

Tagging events are held twice a year, in the fall and spring. The department depends on volunteer anglers to capture fish and carefully transport them to a nearby LDWF surgery boat. There, the fish are weighed, measured, tagged with an external dart tag and surgically implanted with an acoustic tag. Tagged fish are held in a recovery tank for a minimum of thirty minutes to ensure a healthy release.

Acoustic tags are much more effective for tracking fish movement than traditional tagging techniques. Conventional tagging involves marking and releasing a fish that will hopefully be recaptured at a future date, yielding very few data points. Acoustic tagging allows scientists to repeatedly locate and track tagged fish in remote or inaccessible settings, thus providing a more detailed look at patterns, usage and behavior.

Since the program’s inception, biologists have tagged 218 speckled trout, 56 red drum and 18 bull sharks. With four years of data already in hand, the agency has arrived at some interesting conclusions.

Speckled trout movements are most strongly influenced by salinity. The salinity in Lake Pontchartrain is low during the spring, and tagged trout can be observed leaving the lake from March through May. The salinity in the lake begins to rise in the fall, and trout begin returning in November. “Many Lake Pontchartrain anglers reference ‘World Series trout’ because they begin to catch them around the time of the World Series baseball tournament, which occurs in late October to early November,” explained LDWF biologist Ashley Ferguson. “The fall migration observed with the tagged trout correlates very closely with angler observations, lending legitimacy to the fable.”

Biologists have also used acoustic tagging technology to determine that bull sharks in the lake are mostly influenced by temperature and can be observed leaving the lake in cold winter months.

“Red drum have only been tagged for one year of the program. They can be observed using all habitats in the lake but spend a majority of their time along natural shorelines,” explained Ferguson. “We will be tagging additional red drum during this upcoming event to determine how their future behavior compares.”

Movement trends of all acoustically tagged fish can easily be observed using our online Fish Tracker.

Anglers are encouraged to report all tagged fish recaptures. These tagged fish are very valuable to this research project, and we ask that if caught, they be released so that data can continue to be collected. Tagged fish that are part of this program can be recognized by a blue external dart tag. Please call the number provided on the blue tag, and report the date, time, location of catch and health of the fish when released.

Anglers interested in volunteering for the fall tagging event can email aferguson@wlf.la.gov for additional information.

The Louisiana Department of Wildlife and Fisheries is charged with managing and protecting Louisiana’s abundant natural resources. For more information, visit us at www.wlf.la.gov or www.FishLA.org.