Small Investment, Big Returns

By Phil Stevens 

The acoustic telemetry research activities in the Finfish Biology subsection of Marine Fisheries Research continue to deliver . . . in surprising fashion.

Answering concerns expressed by Florida panhandle anglers about the status of cobia in the Gulf of Mexico, a pilot project was conducted in Pensacola, Florida seeking to connect cobia (Rachycentron canadum) research between Gulf and Atlantic waters. And connect it did!

Typically, cobia, a coastal migratory species, are abundant along panhandle beaches during spring. The popular paradigm is that cobia migrate from warm wintering grounds in south Florida towards the productive Mississippi delta. Northern gulf anglers have noted decreases in catches during recent years and tournament records appear to support these anecdotal observations. Partly in response to these concerns, the FWC reduced daily bag limits of cobia in state waters of the Gulf of Mexico. Researchers formed relationships with knowledgeable captains to facilitate this pilot project, creating important relationships upon which future research by FWC and other institutions will be based. Thanks to their eager cooperation, six cobia were tagged with acoustic transmitters off Pensacola and two acoustic receivers were deployed in April 2017.

Tequesta biologist Jim Whittington surgically implants an acoustic tag into a cobia.

The receivers were retrieved by Finfish Biology divers in late May 2018. Logic and experience suggest such a low saturation of transmitters and receivers would have a low probability of yielding meaningful results. But, half of the six cobia were detected on the Pensacola receivers within miles of where they were originally tagged. Another tagged cobia was harvested farther east at Destin, Florida on November 2, 2017. Surprisingly, one Pensacola tagged fish was detected on receivers deployed off Cape Canaveral along the Atlantic coast of east-central Florida!

But it gets even better. The two Pensacola receivers that were deployed detected two cobia that were originally tagged off Cape Canaveral during Aug. 3-4, 2016. One of these was detected on receivers in the Florida Keys, then was detected later at two stations off Pensacola in June and July, 2017. It then returned to the Ft. Pierce area in southeast Florida where it was harvested on December 3, 2017. The other cobia that was tagged at Cape Canaveral was detected on receivers in the Keys, and was last detected off Pensacola on May 1, 2018.

The results of this pilot project with its scant resources have been significantly more fruitful than expected. The boundaries of the Gulf of Mexico cobia stock include southeast Florida based on genetic analysis. What appear to be fairly regular movements of cobia between at least Pensacola and Cape Canaveral supports this stock delineation and provides information on the northern extent of the stock boundary in southeast Florida, which has been uncertain. Expanded research should continue to close knowledge gaps about this important gamefish.