In January, officials opened the Bonnet Carre Spillway on Lake Pontchartrain in Louisiana.
High winter floodwaters led to the decision to open it for 22 days. Normally, the spillway is opened in the spring when fish like trout and redfish are heading to saltier waters to spawn.
Some anglers were concerned that the early opening would force fish to leave the lake.
However, this spring anglers having been catching fish, and now tracking of tagged fish done by the Louisiana Department of Wildlife and Fisheries (DWF) shows that the spillway opening didn’t force the fish out of the lake.
While the fish did change their patterns in relation to the river water, they remained in the lake.
According to biologist Ashley Ferguson, only two of the tagged 26 speckled trout and 28 redfish that were in the lake when the spillway was opened left. Both fish returned.
Ferguson says that the speckled trout appeared to avoid the river plume, and the fish concentrated in a stretch of clear water as the river water spread into the lake.
“The second week (after the opening), when the spillway water had taken that turn along the Hospital Wall, they were mostly all on the North Shore—redfish and speckled trout,” says Ferguson.
Telemetry data was gathered from 90 receivers around Lake Pontchartrain. MODIS satellite images showed the progression of the muddy water.
The fish tracked were tagged as early as 10 days before the spillway opening and as far back as November 2014.