Cobia Researchers use Transmitters as well as Tags to Gather Data on Migratory Patterns
I must admit to having very limited personal experience with Cobia, having caught one sub-legal fish to-date. However, that does not diminish my fascination with the fish, particularly since I ran across a 2019 report from the Gulf States Marine Fisheries Commission titled “Management Profile for Gulf of Mexico Cobia.” This 182-page report is definitely not a quick read and I have thus far only scratched the surface by digging into a few chapters that caught my interest. Nevertheless, it is so full of detailed life history, biology and everything else “Cobia” that it is definitely worth a look. This posting will highlight some of the fascinating aspects of Cobia and why the species is so highly prized by so many people.
Cobia (Rachycentron canadum) are the sole species in the fish family Rachycentridae. They occur worldwide in most tropical and subtropical oceans but in Florida waters, we actually have two different groups. The Atlantic stock ranges along the Eastern U.S. from Florida to New York and the Gulf stock ranges From Florida to Texas. The Florida Keys appear to be a mixing zone of sorts where Cobia from both stocks go in the winter. As waters warm in the spring, these fish head northward up the Atlantic and Gulf coasts of Florida. The Northern Gulf coast is especially important as a spawning ground for the Gulf stock. There may even be some sub-populations within the Gulf stock, as tagged fish from the Texas coast were rarely caught going eastward. There also appears to be a group that overwinters in the offshore waters of the Northern Gulf, not making the annual trip to the Keys. My brief summary here regarding seasonal movement is most assuredly an over-simplification and scientists agree more recapture data is needed to understand various Cobia stock movements and boundaries.
Worldwide, the practice of Cobia aquaculture has exploded since the early 2000’s, with China taking the lead on production. Most operations complete their grow-out to market size in ponds or pens in nearshore waters. Due to their incredible growth rate, Cobia are an exceptional candidate for aquaculture. In the wild, fish can reach weights of 17 pounds and lengths of 23 inches in their first year. Aquaculture-raised fish tend to be shorter but heavier, comparatively. The U.S. is currently exploring rules for offshore aquaculture practices and cobia is a prime candidate for establishing this industry domestically.
Spawning takes place in the Northern Gulf from April through September. Male Cobia will reach sexual maturity at an amazing 1-2 years and females within 2-3 years. At maturity, they are able to spawn every 4-6 days throughout the spawning season. This prolific nature supports an average annual commercial harvest in the Gulf and East Florida of around 160,000 pounds. This is dwarfed by the recreational fishery, with 500,000 to 1,000,000 pounds harvested annually from the same region.
One of the Cobia’s unique features is that they are strongly attracted to structure, even if it is mobile. They are known to shadow large rays, sharks, whales, tarpon, and even sea turtles. This habit also makes them vulnerable to being caught around human-made FADs (Fish Aggregating Devices). Most large Cobia tournaments have banned the use of FADs during their events to recapture a more sporting aspect of Cobia fishing.
To wrap this up I’ll briefly recount an exciting, non-fish-catching, Cobia experience. My son and I were in about 35 feet of water off the Wakulla County coastline fishing near an old wreck. Nothing much was happening when I noticed a short fin breaking the water briefly, about 20 yards behind a bobber we had cast out with a dead pinfish under it. I had not seen this before and was unaware of what was about to happen. When the fish ate that bait and came tight on the line the rod luckily hung up on something in the bottom of the boat. As the reel’s drag system screamed, a Cobia that I gauged to be 4-5 feet long jumped clear out of the water about 40 yards from us. Needless to say, by the time we gained control of the rod it was too late; a heartbreaking missed opportunity. Every time we have been fishing since then, I just can’t stop looking for that short, pointed fin slicing towards one of our baits.
On most days, if you walk to the end of the Navarre Beach Fishing Pier, you will find a group of shark anglers that provide valuable data to the National Oceanic and Atmospheric Administration (NOAA) Cooperative Volunteer Shark Tagging program. Led by Earnie Polk, 50-60 team members have participated in the cooperative tagging program in the twenty-five years he has been involved.
This group not only provides research data to NOAA, but are also stewards of pier etiquette, Navarre Beach and the surrounding area. Tourists and locals alike are treated to stories of local history, fish tales and general information about the area from Earnie and Team True Blue members. In addition, visitors may see a shark tagged and released or the group catching large fish to be used for shark bait
Photo Credit Earnie Polk
The NOAA Cooperative Shark Tagging program has been in existence since 1962. Today thousands of anglers along the Gulf of Mexico and Atlantic Coast have tagged more than 295,000 sharks representing 52 different species. More than 17,500 sharks have been recaptured! This program provides information on shark migration patterns, numbers, locations, migrations, age and growth rates, behavior and mortality.
Earnie estimates he has tagged more than one-thousand sharks for the program. He has refined handling methods to have the least impact on the animal to ensure the survival of the shark after release. The team brings the shark to shore to measure the length and tag the shark just behind the dorsal fin.
Earnie shared an interesting story about tagging at least eighty Dusky sharks during a red tide event during the late fall of 2015. He noticed as the north winds blew the red tide out, an open area was created along the coast. This allowed clear water for the sharks to travel closer to shore and within distance of the tag and release team.
Today, the tiger shark is the most common shark the team tags and releases. Recently, the team tagged and released a 12’6” tiger shark. Randy Meredith, of the Navarre Newspaper agreed to share the video he edited of the Navarre Fishing Pier and the tag and release of the tiger shark in February 2021.
The team uses heavy gear, 200-pound test line and Everol reels that have drag pressure for a shorter fight to reduce stress on the animal for a better survival rate. Gear is spread along the rails at the end of the pier. Baited lines range from approximately 75 to 400 yards off the end of the pier. You probably wonder how they get their line 400 yards off the pier. Earnie has modified a fiberglass kayak with a battery powered motor. It is lowered to the surface of the water; team members drop their lines onto the kayak and Earnie pilots the kayak out to deeper water.
Their strategy is that by dropping more lines, at different depths and locations a shark is bound to trip over one of the lines. They use bait they catch on the pier or other fishing trips. Something big had hit on a cow nose ray over the weekend, so most members were using rays for bait. One team member said, “if the fish had hit on a watermelon, we all would be using watermelon for bait.” These guys have a great sense of humor!!
Make sure that the next time you visit Navarre Beach, you take time to walk out to the end of the fishing pier to learn about local sharks, history and the area from these interesting, funny and helpful anglers. On clear days you may see sharks, rays, sea turtles and other types of marine life as you venture out.
Be sure to stop at the pier store to pay the $1.00 per-person fee to enjoy the view!
Reminder: Spotted seatrout harvest is closed in the Western Panhandle Management Zone the entire month of February.
New regulations were put into place last year reducing bag limits and closing harvest during February in the Western Panhandle Management Zone. For more details see my previous post on the subject.When Spotted Seatrout season is open (months other than February) in the Western Panhandle Management Zone the daily bag limit is 3 per harvester. Harvested Spotted Seatrout must be more than 15 inches long and less than 19 inches long. One fish, per vessel, over 19 inches my be included in the bag limit.
The Western Panhandle Spotted Seatrout Management Zone includes the State and federal waters of Escambia County through the portions of Gulf County west of longitude 85 degrees, 13.76 minutes but NOT including Indian Pass/Indian Lagoon.
Boundary between the Western Panhandle and Big Bend spotted seatrout management zones.
Image source: www.myfwc.com
See myfwc.com for complete information on all game and fish regulations in Florida.
Seagrasses have been described as the “nursery of the sea”. Studies show that up to 90% of the commercially valuable fin and shellfish species spend part, or all, of their lives in these submerged meadows. As you can imagine, these grasses must grow in clear, relatively shallow waters – so they are more inshore. You might also imagine that most of the fish living here are going to be small. There are the larger predators in this grassy world, but most are going to be small enough to hide amongst the blades.
These inshore seagrass meadows not only provide hiding places but provide food as well. Interestingly, most do not feed on the grass directly, but rather the tiny plants and animals that are attached to the blades – what are called epiphytes and epizoids. Those that feed on these are then preyed upon by slightly large creatures until we find the larger apex predators – like the speckled trout.
Many of those who reside here are specialist in camouflage and mimicry, and others might be ones who actually live in the sand bordering the edge of the meadows – waiting for a chance to pounce on unsuspecting food. Let’s meet a few of these interesting fish.
Photo: Nicholls State University
You are at the beach for a day of fun and sun. You enter the water of Santa Rosa Sound to play at the edge of the seagrass bed, or maybe to snorkel and explore it. As you stand on the sand you feel little nips at your ankles and immediately think – CRAB! But you would be wrong. As you look closer you will see it came from a small fish – and the more you stir the sand, more of these small fish arrive. They are probably feeding on the small invertebrates that are stirred up from your movement, but they periodically nip at you as well.
This small fish is a very common member of the inshore fish community known as the pinfish. They are members of the Porgy family, related to sheepshead, and have incisor teeth for crushing the shells of their prey. Most locals are first introduced to them as a kid while fishing. They seem to bite, or steal, any bait you put on. Most often used as bait themselves, they are actually edible – but you need one of the large ones to have a meal. They get their common name from the sharp spines of their dorsal fin. When snorkeling in the grassbeds you will find they are the most common fish there.
These guys look scarier than they are. Long skinny fish with long skinny snouts that hold long skinny teeth. They resemble barracuda and have the look as if they could attack and do some damage – but they are harmless, unless you catch one in a net, then they will swing their long skinny heads towards your hand for snip.
These small predators travel above the grassbeds looking for potential prey hiding among. Small juvenile fish seem to be what they want. Though often just referred to as “needlefish”, there are actually four species, but they are hard to tell apart.
These are captivating fish, and very hard to find as they blend in so well, but they are there – along with their close cousins the pipefish. It seems hard to call it a fish at all – it certainly does not look like one. Swimming vertically in the water, no tail to speak of, they seem like a creature in their own group. But they are fish. The scales are fused into an armor plating and they do have both gills and fins – characteristics of fish. They will use their prehensile tail to grab onto a grass blade, hanging there waiting for tiny shrimp to swim by which they inhale using a vacuum like motion with their tube-shaped mouths.
Pipefish resemble seahorses but are elongated, with a distinct fin for a tail, and swim horizontally as most fish do. They will turn vertically in the grass to appear to be a blade themselves and hunt similar prey as their seahorse cousins.
A well-known characteristic of this group is the fact that the males carry the fertilized eggs – not the females. Males can be identified by the brood sac on their ventral side and they may carry up to 80 eggs. The eggs hatch within the pouch and the young are born alive.
This group of fish are famous for their ability to “blow up”, or inflate like a balloon, when threatened. Kids love to play with them and get a kick out of watching them inflate. These are round bodied – slow moving fish, which is one reason they inflate. It does not matter if you can catch them, you cannot swallow them if you do!
There are actually two different families of “blowfish”. The true puffers are smaller (3-12 inches), have tubercles on their bodies instead of long spines, and the teeth in the upper and lower jaw have a space forming four teeth (two on the top jaw, two on the bottom) – giving them their family name “tetradontidae”. The “burrfish” are larger in size (1-2 feet), have long spines on the body, and no median in the teeth – so only one tooth on the top jaw, one on the bottom – “diodontidae”.
The most common one found is the striped burrfish. The big boy of the group – the 2-foot porcupine fish – is rare in the northern Gulf and prefers the reefs of the open sea to grassbeds.
When threatened they will inflate with water (or air) and try to continue swimming. After the danger has passed, they will deflate and go about their merry way. There are stories about their flesh being poisonous and dangerous to eat – it is true. The compound they produce is one of the more toxic found in the fish world. Though there are certified chefs around the world who can safely clean them, it is not recommended you eat these.
When most people think of reefs, they think of the coral reefs of the Florida Keys and Australia. But here in the northern Gulf the winters are too cold for many species of corals to survive. Some can, but most cannot and so we do not have the same type of reefs here.
That said, we do have reefs. We have both natural and artificial reefs. There are natural reefs off Destin and a large reef system off the coast of Texas – known as the “Flower Gardens”. Here the water temperatures on the bottom are warm enough to support some corals. The artificial reef program along the northern Gulf is one of the more extensive ones found anywhere. There is a science to designing an artificial reef – you do not just go out and dump whatever – because if not designed correctly, you will not get the fish assemblages and abundance you were hoping for. But if you do… they will come.
Reefs are known for their high diversity and abundance of all sorts of marine life – including fishes. There are numerous places to hide and plenty of food. Most of the fish living on the reef are shaped so they can easily slide in and out of the structure, have teeth that can crush shell – the parrotfish can actually crush and consume the coral itself, and some can be fiercely territorial. There are numerous tropical species that can be found on them and they support a large recreational diving industry. Let’s look at a few of these reef fish.
These are fish of legend. There all sorts of stories of large morays, with needle shaped teeth, attacking divers. Some can get quite large – the green moray can reach 8-9 feet and weigh over 50 pounds. Though this species is more common in the tropics, it has been reported from some offshore reefs in the northern Gulf. There are three species that reside in our area: the purplemouth, the spotted, and the ocellated morays. The local ones are in the 2-3 foot range and have a feisty attitude – handle with care – better yet… don’t handle. They hide in crevices within the reef and explode on passing prey, snagging them with their sharp teeth. Many divers encounter them while searching these same crevices for spiny lobster. There are probing sticks you can use so that you do not have to stick your hand in there. There are rumors that since they have sharp teeth and tend to bite, they are venomous – this is not the case, but the bite can be painful.
The massive size of a goliath grouper. Photo: Bryan Fluech Florida Sea Grant
This word is usually followed by the word “sandwich”. One of the more popular food fish, groupers are sought by anglers and spearfishermen alike. They are members of the serranid family (“sea basses”). This is one of the largest families of fishes in the Gulf – with 34 species listed. 15 of these are called “grouper” and there have been other members of this family sold as “grouper”.
So, what is – or is not – a “grouper”. One method used is anything in the genus Epinephelus would be a grouper. This would include 11 species, but would leave out the Comb, Gag, Scamp, Yellowfin, and Black groupers – which everyone considers “grouper”. Tough call eh?
These are large bodied fish with broad round fins – the stuff of slowness. That said, they can explode, just like morays, on their prey. Anglers who get a grouper hit know it, and divers who spear one know it. They range in size from six inches to six feet. The big boy of the group is the Goliath Grouper (six feet and 700 pounds). They love structure – so natural and artificial reefs make good homes for them. They also like the oil rigs of the western Gulf.
An interesting thing about many serranids is the fact they are hermaphroditic – male and female at the same time. Most grouper take it a step further – they begin life as females and become males over time.
The king of finfish… the red snapper
Photo: Florida Sea Grant
The red snapper is king. Prized as a food fish all over the United States, and beyond, these fish have made commercial fishermen very happy. With an average length of 2.5 feet, some much larger individuals have been landed. This fishery put Pensacola on the map in the early 20th century. Sailing vessels called “Snapper Smacks” would head out to the offshore banks and natural reefs, return with a load, and sell both locally and markets in New York. There are large populations in Texas waters and down on the Campeche Banks off Mexico. “Snapper Season” is a big deal around here.
Though these are reef fish, snapper have a habit of feeding above, and away from, them. You probably knew there was more than one kind of snapper but may not know there are 10 species locally. Due to harvesting pressure, there are short seasons on the famous red snapper – so vermillion snapper has stepped in as a popular commercial fishery – and it is very good also. Some, like the gray snapper, are more common inshore around jetties and seawalls. Also known as the black snapper or mangrove snapper, this fish can reach about three feet in length and make a good meal as well.
The white grunt.
Photo: University of Florida
Grunts look just like snapper, and probably sold as them somewhere. But they are a different family. They lack the canines and vomerine teeth the snappers have – other than that, they do look like snapper. Easy to tell apart right? Vomerine are tiny teeth found in the roof of the mouth, in snappers they are in the shape of an arrow. They get their name from a grunting sound they make when grinding their pharyngeal teeth together. A common inshore one is called the “pigfish” because of this. They do not get as large as snapper (most are about a foot long) and are not as popular as a food fish, but the 11 known species are quite common on the reefs, and the porkfish is one of the more beautiful fish you will see there.
Spadefish on a panhandle snorkel reef.
Photo: Navarre Beach Snorkel
This is one of the more common fish found around our reefs. Resembling an angelfish, they are often confused with them – but they are in a family all to themselves. What is the difference you ask? The dorsal fin of the spade fish is divided into two parts – one spiny, the other more fin-like. In the angelfish, there is only one continuous dorsal fin.
Spadefish like to school and are actually good to eat. It is also the logo/mascot of the nearby Dauphin Island Sea Lab.
“Danger Will Robinson!” This fish has a serious set of teeth and will come off the reef and bite through a quarter inch wetsuit to defend their eggs. Believe it – they are not messing around. Once considered a by-catch to snapper fishermen, they are now a prized food fish. They are often called “leatherjackets” due to their fused scales forming a leathery like skin that must be cut off – no scaling with this fish. They have the typical tall-flat body of a reef fish, squeezing through the rocks and structure to hide or hunt. We have five species listed in the Gulf of Mexico, but it is the Gray Triggerfish that is most often encountered.
Photo courtesy of Florida Sea Grant
You may, may not, have heard of this one – most have by now. It is an invader to our reefs. To be an invasive species you must #1 be non-native. The lionfish is. There are actually about 20 species of lionfish inhabiting either the Indo-Pacific or the Red Sea region.
#2 have been brought here by humans (either intentionally or unintentionally – but they did not make it on their own) – this is the case with the lionfish. It was brought here for the aquarium trade. There are actually two species brought here: The Red Lionfish (Pterois volitans) and the Devilfish (Pterois miles). Over 95% of what has been captured are the red lionfish – but it really does not matter, they look and act the same – so they are just called “lionfish”.
#3 they must be causing an environmental, and/or an economic problem. Lionfish are. They have a high reproductive rate – an average of 30,000 offspring every four days. There is science that during sometimes of the year it could be higher, also they breed year-round. Being an invasive species, there are few predators and so the developing young (encapsulated in a gelatinous sac) drift with the currents to settle on new reefs where they will eat just about anything they can get into their mouths. There have been no fewer than 70 species of small reef fish they have consumed – including the commercially valuable vermillion snapper and spiny lobster. There is now evidence they are eating other lionfish.
They quickly take over a reef area and some of the highest densities in the south Atlantic region have been reported off Pensacola. However, at a 2018 state summit, researchers indicated that the densities in our area have declined in waters less than 200 feet. This is most probably due to the harvesting efforts we have put on them. They are edible – actually, quite good, and there is a fishery for them. Derbies and ecotours have been out spearfishing for them since 2010. You may have heard they were poisonous and dangerous to eat. Actually, they are venomous, and the flesh is fine. The venom is found in the spines of the dorsal, pelvic, and anal fins. It is very painful, but there are no records of anyone dying from it. Work and research on management methods continue.
Is this what it sounds like? Fish that do not swim, but drift? Well… yes and no. They can swim, just not very well – they do better by drifting.
The word used most often for any drifting creature in the sea is plankton. Plankton literally means “drifter” or “wanderer”. Most plankton, including planktonic fish, can swim. Some can adjust their position in the water column – rising near the surface at night, sinking deeper during the day.
When you think about it, it is a cool way to make a living out there. With miles and miles of open blue water, the swimming fish must keep swimming. To do this requires a lot of energy, open water fish must consume a lot of high energy food. Drifters just drift. Hang with the currents, enjoying the moment, eating what they can. Sounds pretty good huh?
As you can imagine, there are not many fish who live this lifestyle. Many do after they hatch in their larval stage – but as adults, most live on the bottom, others in the open blue. Let’s meet a couple of the drifters.
The slow moving ocean sunfish.
Now here is one weird looking fish. Large bulbous head, long angular dorsal and ventral fins, and no tail – it’s a swimming/drifting head. These large open water drifters can reach seven feet long, seven feet high, and weigh over a ton. They can hold their position, undulating their dorsal and ventral fins, and move slowly through the water. Often, they will turn on their sides and just hang there. Looking like a floating board or something, small creatures are attracted to them, some of which they eat. Their diet is primarily jellyfish, though they have been known to take small fish, crustaceans, and even algae.
They are related to puffer fish, and actually resemble them early in life, but the resemblance fades quickly as this becomes more head than anything else.
Though rarely seen near shore, they have been, and one was actually spotted inside Pensacola Bay. They occasionally wash ashore dead. One did on Dauphin Island. The staff at the Sea Lab made a mold of the dead creature which is now hanging in the public Estuarium there. Many know this fish by its scientific name – Mola mola – or simply “the mola”. It is a pretty cool fish.
This sargassum fish is well camouflaged within this mat of sargassum weed.
Photo: Florida Museum of Natural History
Sargassum fish are members of a family known as “frogfish” – so you can guess what they must look like – and can guess they are not real good swimmers. Almost completely round, they are blobs in the sea. There are three species in the Gulf, two if which are bottom fish. However, the Sargassum fish is a drifter – drifting with the common seaweed known by its scientific name Sargassum. Sargassum is brown algae that produces air bladders called pneumatocyst. These bladders allow the weed to drift in large mats at the surface where they get sunlight. Some sargassum mats are huge is size and are an ecosystem amongst themselves. Hundreds of miniature fish and invertebrates call this place home – a place to hide in the open sea. It is the home of baby sea turtles, if they can make the trek from the beach alive.
One member of this community is the Sargassum fish (Histrio histrio). It has the typical frogfish shape and look but the coloration matches the Sargassum weed perfectly. Like other frogfish, the first dorsal spine is modified into a “fishing rod” complete with a “lure”. When prey (small creatures in the Sargassum weed) are in view, the Sargassum fish will extend the illicium (as it is called) and actually move it back and forth to make it look like live bait – they are fishing.
Most members of the Sargassum community flee the weed when the currents bring it to close to the beach. However, they hang on longer than you might think. If you are at the beach when the Sargassum is drifting just off the shore – wade out with a small kids dip net and snag a patch. Place in a bucket and see who comes out. You MIGHT get lucky and catch one of these ocean drifters.