Have you ever wondered where fish swim day to day? Or what happened to the fish you caught and released?
Well, thanks to collaborative efforts between Department biologists, anglers and a group of specially tagged fish in Lake Pontchartrain, we’re one step closer to answering these questions.
One particular fish in this special group is a female redfish named Hazel who is marked with blue dart tag number LP223147. The blue tag not only gives her a unique ID as part of the conventional tagging program, but it also marks her as part of this exclusive group.
But why, other than the blue tag, are these fish special? The answer is simple. Hazel is one of many fish that are part of LDWF’s acoustic telemetry tagging program. On November 20, 2014, Hazel was part of a school of redfish busting bait under the birds near the trestles. She was caught using rod-n-reel sampling and underwent surgery to have an acoustic transmitter implanted into her belly. Following the surgery she was released back into the water near her initial catch location, ready to begin transmitting important data including her movement patterns and habitat usage.
Just over a month later on December 29, an angler fishing from his dock on Irish Bayou recaptured Hazel. Fortunately, the angler noticed the blue dart tag, released the fish and called the Louisiana Cooperative Tagging Program to report the recapture. As we do for all recaptures, a recapture report was generated to show the location where Hazel was initially released and where she was recaptured – a distance of over 4 miles.
Conventional tagging data provides us with a snapshot of information. It shows us where the fish was the day it was tagged and its location when a lucky angler recaptured it. In reality, fish don’t swim in straight lines, simply moving from point A to B.
Once tagged, where did Hazel travel before she was recaptured? As part of the acoustic tagging program, the internal transmitter (acoustic tag) inside Hazel shed a bit more light on how she arrived at her recapture point in Irish Bayou.
Acoustic telemetry data shows Hazel was quite the traveler before ultimately heading for Irish Bayou. Information from the first data download was hand plotted to create a track showing Hazel’s estimated movements. From the trestles, she headed to the North Shore by Eden Isles, and then went east towards Hospital Wall. From there, she cruised around the open water of the middle grounds, stopped off by the dredge hole near the South Shore and eventually made her way into Irish Bayou.
One thing to be mindful of when looking at acoustic telemetry tracks is that the lines between receiver detections are more like connect-the-dots, rather than the exact a fish takes. Remember, fish don’t swim in straight lines. The detections let us know that she was near a receiver (within half a mile), and the line on the map indicates the next detection point. There are many places a tagged fish can swim between detections, but what the lines do provide is the relative direction, movement patterns and habitat types frequented by these fish.
For instance, we can see that Hazel traveled much further than the 4-mile straight shot from the trestles to Irish Bayou. She took a more scenic route over the course of a month, passing through various habitat types including shorelines, open water and dredge holes. She also seemed to have a preference for the eastern portion of Lake Pontchartrain during her first month of travel after being tagged.
Where did Hazel go next? To find out, we invite you to visit our new fish tracking webpage. Recently developed as a way for the public to view our telemetry tagging efforts, the unique fish tracking feature uses an interactive map allowing visitors to visualize the daily movements of multiple fish species. Not only can you view Hazel’s tracks, but you can also compare them to other fish tagged in Lake Pontchartrain including other redfish, speckled trout and bull sharks.
We are proud to showcase this innovative visualization tool. The online interface allows anyone to better understand a day in the life of a fish. In the case of Hazel, we can see a much clearer picture of where she went after she was both tagged and recaptured. After her November cruise throughout the middle grounds, Hazel left the system via Chef Pass on the night of December 2. The next night she came back into Chef Pass, and over the course of the next evening into morning, she made her way back into Lake Pontchartrain. From there, she continued to move around the same general area of the southern middle grounds, trestles, south point and passed near the mouth of Irish Bayou no less than 15 times before she was caught and released.
Throughout the cold winter months, Hazel spent a good amount of time near a deep dredge hole, sometimes making daily visits to Irish Bayou and open water areas. As it warmed up in the spring of 2015, her movement rate increased, but the general trend is that she hung out in the southern middles grounds of eastern Lake Pontchartrain. Her tendencies are in stark contrast to another female redfish tagged the same day named Goldie. While Hazel remained in southeast corner of the lake, Goldie virtually took a tour of the entirety of Lake Pontchartrain. From the initial tagging location near the trestles she hit Bayou Lacombe, Goose Point, multiple spots on the causeway, as well as areas on the north, east, and south shores. The final detection that we have processed shows Goldie leaving the system through the Rigolets in May of 2015.
Stay tuned for future improvements to our tracking technology and the incorporation of environmental data including lunar cycles, temperature, salinity and storm events.
Tracks of offshore species like tarpon, yellowfin tuna, tiger sharks, scalloped hammerheads and even whale sharks are also available.
Click here to learn more about LDWF’s fish tagging programs.
