Everyone knows that an abundance of food is an effective way to keep animals around.
After all, a bowl of cat food on your porch will keep the neighborhood felines coming back for weeks, if not months. Take my word for it.
But a certain fish in north Louisiana has garnered attention of LDWF biologists by possibly willingly passing up a source of nourishment.
“They’ve got all the food in the world right here, and we’re just wondering why would they leave this all-you-can-eat buffet,” LDWF biologist Ryan Daniel said.
Stocked into Bayou DeSiard periodically since 2013, these 4,500 grass carp have not been eating the food readily available to them because they’ve left or because they’ve died. The species was introduced in hopes of reducing unwanted aquatic vegetation to facilitate boat navigation in this bass, crappie and bream fishing hotspot. Surprisingly, we’ve seen little to no reduction of the troublesome vegetation, frustrating local residents and fishermen, alike.
“They feed in large schools. Fish this size are very easy to see, but we’re just not seeing them out there. We also haven’t seen the reduction in vegetation growth we hoped to see by now,” Daniel said. He added that electrofishing samples have confirmed very few grass carp remain in the food-rich area.
The mystery has led to our latest telemetry tagging project – the tracking of grass carp in Monroe’s urban fishery.
LDWF biologists insert a telemetry tag into a grass carp prior to dropping it - and nine of its counterparts - into Bayou DeSiard.
Telemetry tags are tracking devices that can be inserted inside a fish or exteriorly attached to a fish to monitor its movements. Telemetry tags allow biologists to track fish continuously rather than be restricted to points of catch and release.
On March 17, biologists released 56 grass carp into Bayou DeSiard, 10 of which were telemetry tagged. Since the stocking, biologists have been tracking and will continue to track the movements of the tagged fish by boat with a hand-held receiver over the course of a year or longer, depending upon battery life.
Daniel hopes that this project will provide insight into why sampling efforts have resulted in very low numbers of the carp. Fishery managers will then be able to use the information from this study to determine if it is beneficial to continue to stock grass carp into the waterbody or employ other vegetation control efforts. Additionally, if containment measures are deemed necessary and couldn’t be installed at a reasonable cost, biologists may have to abandon this form of vegetation control.
Biologists speculate that a lack of oxygen during hot summer months may temporarily displace the fish, but this doesn’t explain their absence during the majorly of the year.
If the grass carp are leaving by choice, biologists have narrowed their escape routes to three possibilities. They either left through a culvert on the northern portion of the waterbody into Bayou Bartholomew or a culvert just south of Frenchmen’s Bend into Blake Bayou Lake. The carp may have also traveled south down the waterbody, however Daniel thinks this is unlikely because of the lack of food in that portion of Bayou DeSiard.
Excess vegetation has plagued the northern portions of Bayou DeSiard since the 1970s. Potential remedies include widening, dredging and tree removal but would likely be too costly. As a result, officials have resorted to herbicide applications. LDWF also stocked a small number of grass carp into the bayou about 20 years ago; however, barriers designed to keep the carp within the confined area failed.
Biologists hope that this telemetry project will determine whether grass carp are a viable option in Bayou DeSiard.
