around Pontchartrain based on the ever-fluctuating salinity, temperature, and turbidity.
Generally, there is a west to east, low to high,
salinity gradient in the lake. Freshwater enters
Pontchartrain through Lake Maurepas along
with several rivers and bayous on the
Northshore, whereas saltwater creeps in
through the Rigolets and Chef Pass. While
various salinity tolerances navigate
through the lake, finding their preferred water parameters.
In 2012 the Louisiana Department of Wildlife & Fisheries (LDWF)
partnered with Louisiana State University (LSU) to deploy an acoustic
telemetry project in Lake Pontchar-
Acoustic tagged fish locations overlaid with MODIS satellite image, January 29, 2016.
rainfall influences the amount of freshwater
flowing into the lake, it is the wind rather than
the lunar tide that drives the ebb and flow of
salinity levels throughout the lake. A moder-
Release of a red drum into
Lake Pontchartrain after recovering from tagging surgery.
The R/V Percy Viosca, Jr. serves as the LDWF surgery boat.
train that would provide a clearer picture of
fish migration patterns and habitat uses. In
order to accomplish this, ninety hydrophones,
called receivers, were strategically placed
“Salinity is the strongest influence on
speckled trout movements in the lake,
followed by temperature.”
ate to strong west wind for a week or so will
push fresh water further into the main body of
Pontchartrain, allowing a wider spread of
freshwater species. Likewise, a steady east
wind will drive saltier water into the reaches of
the lake. The many transient fish species with
throughout the lake, covering artificial reefs,
shell pads, open water, passes, grass beds,
and dredge holes. After the receivers were
deployed, tagging events were held where
speckled trout and redfish were implanted
with acoustic tags. When a tagged fish
passes within a half mile of the submerged receivers, a pinging noise, created by the tag, is
translated into the date, time, and unique fish
identification number. The information is
recorded and stored within the receiver until
researchers visit and download the data, typically within six to eight weeks. An enormous
amount of data is collected each time the receivers are downloaded. The data, coupled
with water quality and weather information,
begins to paint a picture of what areas of the
lake fish inhabit and why.
Recently, the question of which habitat
speckled trout prefer was answered by Noelle
Bramer, who recently completed her Masters
research with LSU. She performed water qual-
Continued on page 34
April 2016 www.marshandbayou.com PAGE 33