Tagging redfish, trout helps biologists track growth, movement _lowres

 

When New Orleans attorney T. Maumus Claverie decided it was time to collect data on a species like redfish, he knew he had to do it himself.

Back in the late 1980s, few knew the benefits of applying a tag to a fish to study where the fish lived, where it went and how big a it could grow in a year or two.

“T-Mau ran the whole show out of his office, getting the tags and getting fishermen to use the tags, collecting the data,” Wildlife and Fisheries assistant secretary Randy Pausina said.

Some 10 years later, when Pausina took over the LDWF’s Finfish Program, he went to Claverie, who was working in a federal-level program for small gamefish. He knew it was time for his crew to get involved. CCA-Louisiana was helping Claverie, but Pausina knew those thousands of tags already attached to swimming redfish held a wealth of knowledge.

So with CCA providing the private-sector help, LSU and UNO scientists lent their expertise in labs and on the water. With the LDWF spearheading the drive, the redfish tagging program went into another gear. Today, 25 years after Claverie introduced tagging to the state’s coastal anglers, tags remain an important part of state biologists’ redfish study, and, through the Louisiana Saltwater Series, has spread to speckled trout.

Pausina said tags are used to study different aspects of these two species, but, he said, “The bottom line is (tags) give us good movement and migration patterns, and, if there are enough tagged fish, we can get more accurate estimates of population size and mortality, and those are two of the most difficult things to study with any fish species.”

Pausina said the Tagging Program has expanded past a dedicated angler inserting a ribbon tag into the fish near its dorsal fin.

In another partnership with university studies in Calcasieu Lake, then in Lake Pontchartrain, fish are being fitted with acoustic tags. Monitoring buoys in the lakes chart each tagged fish when it swims near the buoy. Pausina said this program “fills in the in-betweens of a fishermen catching, tagging and releasing a fish and another angler recapturing that fish.

Current Tagging Program coordinator Heather David, a LDWF biologist, said the program works because anglers are more involved.

“They want to help. They use the tags, record the data needed, and want to know where their fish are going. When one of their (tagged) fish is recaptured, we tell them where it went (and) how much it grew,” David said.

To fill in Pausina’s “if there are enough fish” part of this fishery equation, David said more than 105,000 redfish have been tagged in Louisiana’s coastal waters since the 1980s.

While part of any biological study involves killing a fish to study its age and growth rates, David said the state’s extensive data bank on redfish and trout has enough numbers to come close to comparing length to weight and to the age of a captured, then recaptured redfish or trout. She said they have studied a redfish that was 43 years old, its age calculated by counting rings on the fish’s otolith, a free-floating bone that grows in the fish’s head.

“We are taking what the anglers give us, analyzing the information. It helps us find population structure, growth rates, habitat preferences and movement patterns from point A to point B and, maybe, to point C,” David said. The program also give biologists a chance to determine if there’s an equal age distribution among these species’ populations.

“(Movement) depends on the species, but we see a lot of redfish, and not many of them travel a mile or two from where they were released,” David said. “They’re sticking around where originally released, so it’s apparent that they’ve got food there, the water is right and they’re happy in that place.”

David said most tags are shed by the fish within two years. Muscle growth pushes the tags from the muscle and back through the skin. She said most tags a fishermen will see in Louisiana tagged fish are yellow, but some older tags are white and some green.

“This is a program that is a great source for the department (LDWF) and for the anglers,” Pausina said. “The anglers who volunteer to tag fish means a big savings for our department and we wouldn’t have the data we have now without them.”