Powers Leads Study on Cobia and Tripletail in the Gulf

By DAVID RAINER, Alabama Department of Conservation and Natural Resources

Two saltwater species with little research data will now be the focus of a $5 million study that will encompass all five Gulf states. Dr. Sean Powers of the University of South Alabama (USA) will lead a team to study cobia, a species that had great popularity among anglers several decades ago, and tripletail, a species that has been increasingly targeted in recent years.

Powers, the Director of the Stokes School of Marine and Environmental Sciences at USA, said Alabama Senator Katie Britt and her staff were able to shepherd this funding from the National Marine Fisheries Service to the Gulf States Marine Fisheries Commission (GSMFC) for species that don’t garner national attention. He and Commissioner Chris Blankenship of the Alabama Department of Conservation and Natural Resources (ADCNR) were elated when the grant was announced last week.

“The reason Commissioner Blankenship and I are so excited is we’ve been talking to Senator Britt’s staff about some money to study species that are important to the (Gulf) states but seem to not be priorities for the National Marine Fisheries Service,” Powers said. “This money will be used to address problems from the states’ perspectives. The Senate requested that NMFS study species that didn’t have a lot of data on these, what we call,  data-poor species. They are not encountered nearly as often as species like speckled trout and redfish. We just don’t know enough about them to manage them properly. 

“Tripletail definitely falls in that category, cobia as well. The thing about those two species is that tripletail are being targeted more and more. For cobia, there’s been a lot more effort directed at those fish during the past decade.”

The success of cobia anglers varies significantly by location. Several decades ago, anglers on the Alabama Gulf Coast geared up for a spring cobia run that produced abundant catches, including state record fish. That migration has fallen to a trickle today, and the study will try to determine why. Cobia is a federally managed species but they are rarely caught farther than 3 miles off the coast. Cobia must be 36 inches fork length, measured from the fork in the tail to the tip of the mouth. The daily bag limit is one per person, not to exceed two per vessel.

“Having grown up on the Alabama Gulf Coast, I can remember how excited anglers were about the cobia spring run,” Commissioner Blankenship said. “Many people had towers on their boats to be able to spot the fish as they cruised down the coastline. Since that time, the migration has waned to the point that it’s not dependable. Strict management measures have helped cobia recover, but we need to understand much more about the migration, which this study is designed to do. I look forward to seeing the results from Dr. Powers and his team.”

Powers said the health of the cobia population depends on location.

“Cobia is really interesting because if you talk to people along the Chesapeake Bay and the Atlantic, they’re having some of the best cobia catches they’ve ever had,” Powers said. “When you talk to people along the Gulf Coast, they don’t see the big migration in that April window that used to happen. Cobia, we think, for the most part, migrate from southern Florida around the Gulf Coast in April, stay until fall and then go back to the Keys. That’s what we thought for a long time.”

Anglers on the northern Gulf used to set their calendars for the second or third week in April to make sure they had time to chase cobia along Alabama’s beaches.

“We’ve noticed that migration has become less and less distinct,” Powers said. “We don’t know if this is new or not, but we’re seeing evidence there may be a different type of cobia. We call these ‘contingents’ if they have a different behavior and life history. This different contingent seems to stay along the Gulf Coast and kind of migrates north and south. If it gets cold, they just go to that deep water offshore. When it warms up, they’ll come back. So, we call that a resident population. There’s evidence for that off of Alabama and Mississippi, and we have new evidence that is the case off Texas.

“We want to know if we have a migratory contingent of cobia and this resident contingent. And we want to know how heavy the fishing pressure is.”

Commissioner Blankenship added, “In years past, tripletail were targeted by a handful of people. These days, with the onset of social media, the popularity of this tasty fish has exploded and everybody is trying to catch one. This data will help determine if our current management efforts are enough to sustain the population or whether changes need to be made.”

To acquire the data needed, Powers said there will be a massive effort to tag both species this spring and summer.

“We want to tag about 500 of each of those species,” he said of the Gulf-wide effort. “We’ll use conventional tags, acoustic tags and satellite tags. I’m leading the effort, but we’re partnering with all five Gulf states. The goal off Alabama is to tag 100 cobia and 100 tripletail.”

The information published nine years ago by GSMFC indicated very little is known about the biology and life history of tripletail, including age and growth, reproductive biology, seasonal movements and migratory patterns. This pelagic species can be found from the northern Gulf and associated estuaries all the way to Argentina and is usually associated with some type of structure, like buoys and channel markers, or sargassum grass in the open water. Tripletail are a state-managed species. Alabama’s daily bag limit is three fish per person with an 18-inch minimum fork length.

“The interesting thing we want to know about tripletail is, do all the tripletail come in from the sargassum or is it just a percentage?” Powers said. “We’re going to spend a lot of time tagging tripletail out in the sargassum, where we know they are during the colder months. Then we’re going to tag a bunch in the estuaries, like Mobile Bay and Mississippi Sound.

“Tripletail are really targeted now. They’re fun to catch and great to eat. If only 10 or 20 percent are coming inshore to the bays and most of them stay offshore, then I’m not that worried about how much fishing pressure we have in the bays. If it turns out that almost all of them are coming into the bays and then going back to the sargassum, then we have to worry a little bit about tripletail.”

Another dataset Powers will seek during the study will be the spawning activity of tripletail.

“We think they come into the bays to beef up on the menhaden and abundant prey available, and then they go offshore to spawn,” he said. “There’s some evidence they do that repeatedly. It’s not just one migration; it’s several migrations on and offshore. That is some of the information we need to know. With the fishermen calling in their tags, we will also get an idea of the exploitation rate, what the fishing mortality is. 

“These are two very cool species that we need more information on. We’re very specific about what we need. The tagging allows us to understand movements, migrations and fishing mortality.”

Powers said the initial funding will focus on getting the tagging goals accomplished. Follow-up funds will be used to study the data collected.

“We have to wait on the data from the acoustic and satellite tags,” he said. “Some of the satellite tags will be programmed to last 12 to 18 months. We’re going to be out there tagging in April to make sure we catch the migratory cobia. Tripletail won’t start coming in until it gets a little warmer. We will probably be tagging fish from April until September or October, depending on the weather.

“We’re really excited that ADCNR and Commissioner Blankenship have helped bring attention to this. Anglers will see us (USA and Dauphin Island Sea Lab) out there. They will see the tags, and we will definitely learn a lot about these two species.”

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