When you look over the species of sea basses and groupers from the Gulf of Mexico it is a very confusing group. Hoese and Moore1 mention the connections to other families and how several species have gone through multiple taxonomic name changes over the years – its just a confusing group.
Photo: National Oceanic and Atmospheric Administration
But when you say “grouper” everyone knows what you are talking about, and everyone wants a grouper sandwich. This became a problem because what people were serving as “grouper” may not have been “grouper”. And as we just mentioned what is a grouper anyway? The families and genera have changed frequently. Well, this will probably get more technical than we want, but to sort it out – at least using the method Hoese and Moore did in 1977 – we will have to get a bit technical.
“Groupers” are in the family Serranidae. This family includes 34 species of “sea bass” type fish. Serranids differ from snappers in that they lack teeth on the vomer (roof of their mouths) and they differ from “temperate basses” (Family Percichthyidae) in that their dorsal fin is continuous, not separated into two fins. These are two fish that groupers have been confused with.
Banked Sea Bass.
Photo: National Oceanic and Atmospheric Administration.
We can subdivide the serranids into two additional groups. The “sea basses” have fewer than 10 spines in their dorsal fin. There are 10 genera and 18 species of them. They have common names like “bass”, “flags”, “barbiers”, “hamlets”, “perch”, and “tattlers”. They are small and range in size from 2 – 18 inches in length. Most are bottom reef fish with little commercial value for fishermen. Most are restricted to the tropical parts of the Atlantic basin but two are only found in the northwestern Gulf, one is only found in the eastern Gulf, and one has been found in both the Atlantic and Pacific. The biogeography of this group is very interesting. The same species found in both the Atlantic and Pacific suggest an ancient origin. The variety of serranid sea bass suggest a lot of isolation between groups and a lot of speciation.
The ”groupers” have 10 or more spines in their dorsal fin. There are two genera in this group. Those in the genus Epinephelus have 8-10 spines in their anal fin and have some canine teeth. Those in the genus Mycteroperca have 10-12 spines in their anal fin and lack canine teeth. Within these two genera there are 15 species of grouper, though the common names of “hind”, “gag”, “scamp” are also used. Most of these are found along the eastern United States and Gulf of Mexico. Five species are only found in the tropical parts of the south Atlantic region, five are also found across the Atlantic along the coast of Africa and Europe, and – like the “sea bass” two have been found in both the Atlantic and the Pacific. They range in size from six inches to seven feet in length. The Goliath Grouper can obtain weights of 700 pounds! Like the sea bass, groupers prefer structure and can live a great depths. Unlike sea bass they are heavily sought by commercial and recreational anglers and are one of the more economically important groups of fish in the Gulf of Mexico.
The massive size of a goliath grouper. Photo: Bryan Fluech Florida Sea Grant
One interesting note on this family of fish is that most are hermaphroditic. The means they have both ovaries (to produce eggs) and testes (to produce sperm). Sequential hermaphrodism is when a species is born one sex but becomes the other later in life. This is the case with most groupers, who are born female and become male later in life. However, the belted sand bass (Serranus subligarius) is a true hermaphrodite being able to produce sperm and egg at the same time – even being able to self-fertilize.
For many along the Florida panhandle, their biogeographic distribution and sex do not matter. It is a great tasting fish and very popular with anglers. For those with a little more interest in natural history of fish in our area, the biology and diversity of this group is one of the more interesting ones.
1 Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M Press. College Station TX. Pp. 327.
Snook… Wait did you say Snook in the Florida panhandle?
Yep… they are not common, but they have seen here.
For those who do not know the fish and do not understand why seeing them is strange, this is a more tropical species associated with tarpon. In the early years of tourism in Florida tarpon fishing was one of the main reasons people came. Though bonefish and snook fishing were not has popular as tarpon, they were good alternatives and today snook fishing is popular in central and south Florida… but not in the north.
This snook was captured near Cedar Key. These tropical fish are becoming more common in the northern Gulf of Mexico.
Photo: UF IFAS
This fish is extremely sensitive to cold water, not liking anything under 60° F. They frequent the same habitats as tarpon, mangroves and marshes. They are euryhaline (having a wide tolerance for salinity) and can be found in freshwater rivers and springs. Actually, near river mouths is a place they frequent. The younger fish are more often found within the estuaries and adults have been found in the Gulf of Mexico. Again, this is a more tropical fish with records in Florida north of Tampa being rare. In the western Gulf the story is the same, almost all records are south of Galveston, Texas. Until recently…
Hoese and Moore1 cite a paper by Baughman (1943) that indicated the range of the fish had actually moved further south. One reason given was the loss of the much-needed salt marsh and mangrove habitats from human development. But in recent years there have more reports north of Tampa. Purtlebaugh (et al.)2 published a paper in 2020 indicating an increase in snook captured in the Cedar Key area of the Big Bend beginning in 2007. At first records only included adults, and the thought was these were “wayward” drifters in the region. But by 2018 they were capturing fish in all size classes and there was evidence of breeding going in the area. The range of the fish seemed to be moving north. The study suggests they still need warm water locations to over winter, and, like the manatees, springs seem to be working fine. But another piece of the explanation has been the reduction of hard freezes during winter in this part of the Gulf. Climate change may be playing a role here as well.
There seems to be other tropical species dispersing northward in a process some call “tropicalization” including the mangroves. There have been anecdotal reports of snook near Apalachicola where mangroves are becoming more common, and I know of two that were caught in Mobile Bay. There are mangroves growing on the Mississippi barrier islands as well. While explaining this during a presentation I was doing for a local group, a gentleman showed me a photo of a snook on his phone. I asked if he caught it in the Pensacola area. He replied yes. When I asked where, he just smiled… 😊 He was not going to share that. Cool.
There is no evidence that snook have established breeding populations are in our waters. Especially after this winter with multiple days with temperatures in the 30s, it is unlikely snook would be found here. But it is still interesting, and we encourage anyone who does catch one, to report it to us.
1 Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M Press. College Station Tx. Pp 327.
2 Purtlebaugh CH, Martin CW, Allen MS (2020) Poleward expansion of common snook Centropomus undecimalis in the northeastern Gulf of Mexico and future research needs. PLoS ONE 15(6): e0234083. https://doi.org/10.1371/journal.pone.0234083.
At the time of this writing, red tide is still lingering off the Pensacola coast. By the time this is posted it may or may not be. I have had a few questions about red tide while this has been occurring here, and some misconceptions about it – so, now is a good time to try and set the story straight.
The dinoflagellate Karenia brevis.
Photo: Smithsonian Marine Station-Ft. Pierce FL
Red tide is actually caused by a group of small, single-celled marine plants. The one responsible for the red tide in the Gulf of Mexico is called Karenia brevis. Karenia is a naturally occurring dinoflagellate. If I were to pull a water sample off of Pensacola Beach right now I would find it there – albeit in small concentrations – say 300-500 cells in a liter of water. At these concentrations there are no problems. When we say problems, we mean respiratory problems or fish kills. See, Karenia is a dinoflagellate that when irritated or disturbed, will release a toxin – brevotoxin. This toxin is a neurotoxin that is known to kill fish, sea turtles, and marine mammals at high concentrations – greater than 1,000,000 cells / liter. For humans the issue is more of respiratory and eye irritation. Though consuming filter feeding shellfish, such as oysters and scallops, during a red tide can cause serious gastrointestinal problems and possibly hospitalization in humans. This is why the state closes shellfish harvesting when Karenia concentrations reach 5,000 cells / liter.
What causes Karenia concentrations to increase from 500 cells to 5,000 cells, or even 1,000,000 cells / liter?
The same thing that causes all plants to grow – sunlight and nutrients.
Here is where the first misconception arises.
“Red tides are caused by the increase of nutrients in the ocean due to human activity”.
Not exactly correct. Red tides have occurred in the Gulf of Mexico since the colonial period, and the colonists certainly did not discharge enough nutrients to spawn a red tide bloom. No, these blooms occur naturally. Most form off the coast of southwest Florida. There the continental shelf extends about 200 miles offshore before reaching the slope to the deep sea. At this slope there are upwelling currents bringing nutrients from the seafloor to bath these phytoplankton in the warm Florida sun. This combination, along with some other water chemistry needs, fuel the growth of phytoplankton from a few hundred cells / liter to a few thousand, hundred thousand, or even a million cells / liter – an algal bloom. At concentrations of 1,000,000 cells or more the water actually changes color to reddish – hence the name “red tide”.
Today humans ARE discharging large amounts of organic and inorganic nutrients into local waterways. These eventually make their way to the Gulf and can enhance a natural bloom from say 10,000 cells / liter to over 1,000,000 – we can make the situation worse. This typically happens when offshore winds blow the naturally occurring red tides closer to shore to meet our “cocktail of nutrients” and wa-la – an enhanced bloom with enhanced problems.
Dead fish line the beaches of the Florida Panhandle after a coast wide red tide event in October of 2015.
Photo: Randy Robinson
Here in the northern Gulf the conditions to spawn naturally occurring red tides do not typically exist. What we usually see are the blooms generated in southwest Florida pushed northward but weather patterns. At the time of this writing, Escambia County is experiencing a red tide offshore at background/very low concentrations (0-10,000 cells/liter). Though are no reports of fish kills or respiratory issues in humans, but these are happening to our east in Okaloosa, Walton, Bay, and Franklin counties.
The state is aware of the not only the red tide situation, but other harmful algal blooms occurring around the state and has a task force to try and address these. We, of course, can help by reducing the amount of nutrients (fertilizers) we discharge into our local waterways. This would include not only commercial fertilizers, but any plant and animal waste.
Red Tide Current Status. 2021. Florida Fish and Wildlife Conservation Commission. https://myfwc.com/research/redtide/statewide/?utm_content=&utm_medium=email&utm_name=&utm_source=govdelivery&utm_term=campaign.
Eels… when that name comes up most think of either the vicious moray eels or the famous electric eel. Moray eels do exist in the Florida panhandle, and we will talk about them. Electric eels do not, they are found in the Amazon River system. That said, we do have eels here – quite a few. There are at least 18 species found in six different families. Most are 2-3 feet in length, though the Banded Shrimp Eel (Ophichthus) can reach six feet. About half of them are found offshore on the middle and outer shelves, the other half can be found in the inner shelf and estuaries, a few species swim into freshwater. Shrimpers often catch them when trawling and occasionally anglers will catch them with rod and reel.
Eels superficially resemble snakes and sometimes are confused with them. I have been told more than once that we do have sea snakes here. We do not. What people are finding are one of the 18 species of eels in the area. We do have snakes swimming across our estuaries, but we do not have sea snakes.
Eels differ from snakes primarily in that they, being fish, possess gills – not lungs. Most eels do have sharp teeth, the morays are famous for theirs, but no eels are venomous – so no worries there. Most of our eels have very small scales or are completely scaleless and are often very slimy and difficult to handle. They have been used as bait and one species, the American eel (Anguilla rostrata), has been used for food.
The Anguilla eel, also known as the “American” and “European” eel.
The American eel has an interesting life history. They spawn in the Sargasso Sea, an area in the middle of the Atlantic Ocean. Their developing leptocephalus larva are thin, flat, and transparent in the water. They drift with the ocean currents into the Gulf of Mexico and eventually into our estuaries. I have found them along the shores of Project Greenshores (in Pensacola Bay) during certain parts of the year. From here they work their ways into our local rivers where people encounter the large adults. I have found them living in submerged caves near Marianna and many locals have found them at the bottom of our rivers. When time to breed, the adults will leave and head back to the open Atlantic to begin the cycle again. An amazing trip.
Moray eels are famous for the nasty attitudes and vicious bites. They are more tropical and associated with offshore reefs, though the ocellated moray (Gymnothorax ocellatus) is often caught in shrimp trawls. They live in the crevices of the reef ambushing prey. Some, like the green moray, can get quite large – over six feet. Like all eels, they have very powerful muscles and sharp teeth.
The shrimp eel is common on our inner and middle continental shelf.
Conger eels are very common despite few people ever seeing them. There are six species and they frequent the middle continental shelf, so are rare in estuaries.
There are eight species of snake, or worm, eels. These are more common on the inner shelf and the coastal estuaries. Many prefer muddy bottoms where they bury tail first to ambush prey swimming by.
The majority of these marine eels have a large geographic distribution. Their larva can be carried great distances in the currents and their need for sandy or muddy bottoms can be met just about anywhere. They appear to have few barriers keeping them from colonizing much of the Gulf and surrounding waters. Most fall into the category we call “Carolina Fish”. Meaning their distribution occurs from the Carolinas, throughout the Gulf of Mexico, south to Brazil. There are a few species that can tolerate the lower salinities of the estuaries and one, the Anguilla eel, that can even venture into freshwater.
There are few species restricted to the tropical reefs, such as the morays. But morays are found on our smaller middle shelf and artificial reefs in the northern Gulf. Though found in parts of the Atlantic Ocean, Hoese and Moore1 reported one species of conger eel, Uroconger syringus, as only occurring near south Texas in the Gulf of Mexico. What barriers keep it from colonizing other Gulf habitats is unknown.
Eels are true fish that we rarely encounter. Encounters are usually startling but exciting at the same time. They are pretty amazing fish.
Hoese, H.D., R.H. Moore. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M University Press, College Station TX. Pp. 327.
A great blue heron enjoying the Gulf of Mexico.
Photo: Chris Verlinde
June is National Ocean Month. Close your eyes and think about just how many oceans there are. Surprise, there is only one! The ocean is huge, covering over 70 percent of the earth’s surface. Traditionally, the ocean was divided into four named ocean basins: the Pacific, Atlantic, Indian, and Arctic. However, most countries, including the United States, now recognize the Southern (Antarctic) as the fifth ocean. No matter where you live, you are connected to our one global ocean.
What do you know about our ocean? The ocean is where life began over 3.5 billion years ago. The ocean covers over 70% of the Earth’s surface and includes over 96% of the Earth’s water. Australia’s Great Barrier Reef is the largest living structure on Earth and can be seen from the moon! The deepest part of the ocean is in the Mariana Trench, and nearly 7 miles beneath the waves! Coral reefs cover only 1/50th of the ocean floor but about one quarter of all the marine species make coral reefs their home. No light penetrates the ocean at depths greater than 3,280 feet. Aided by deep diving rovers and remote sensing cameras, scientists are still discovering new species beneath the waves. The Gulf Stream transports more water than all the Earth’s rivers combined. The mid-ocean ridge crisscrosses the globe for over 40,000 miles and is the largest geological feature on Earth. Did you know that about 95% of the ocean remains unexplored?
What about our beloved Gulf of Mexico? Is it an ocean? No! While both oceans and gulfs are large bodies of saltwater, gulfs are smaller and are bordered on three sides by land. In the case of the Gulf of Mexico, it’s bordered by the United States and Mexico. So, although it is large and salty like the ocean, the Gulf of Mexico is considered part of the Atlantic Ocean.
Happy National Oceans Month!
Reference: National Oceanic and Atmospheric Administration https://oceanservice.noaa.gov/ocean/30days/welcome.html
The equatorial currents of the Pacific.
In our continuing series on the biogeographic distribution of island vertebrates, this week we look at a creature that, for some, is as scary as sharks – the rays. The term stingray conjures up stinging barbs and painful encounters, and these have happened, but rays are easily scared away by our activity. Occasionally people will step on one and the venomous spine is used to make you move your foot. You can avoid this by shuffling your feet when moving across the sand. Rays detect the pressure and move before you reach them. Again, negative encounters with rays are not common.
The Atlantic Stingray is one of the common members of the ray group who does possess a venomous spine.
Photo: Florida Museum of Natural History
There are 18 species of rays (from 9 families) found in our area. An interesting note, only eight of those possess a barb for stinging, and five are from the family Dasyatidae (the stingrays). Others that have barbs include the butterfly ray, cownose ray, and the eagle ray.
Rays are related to sharks but differ in that (a) the pectoral fin begins before the gills slits, and (b) the gill slits are on the underneath of the body – not on the side as found in sharks. Shark distribution seems to be controlled by water temperature. We see this with ray distribution as well, but interestingly the skates seem to be restricted to the Gulf of Mexico. Some are found almost exclusively in the east or west side of the Gulf.
Skates resemble stingrays but lack the venomous barb. They will usually have small thorns on their bodies and lay their developing embryos in a leathery egg case folks call “mermaid’s purse” when they wash ashore. There are four species found in the Gulf, but the spreadfin skate is ONLY found in the Gulf of Mexico and is not found along the Florida peninsula. The clearnose skate, which can be found all along Florida and the eastern seaboard of the U.S., is absent from western Gulf. It is interesting to try and understand why. What barrier keeps these two skates from colonizing the entire Gulf?
There is a large plume of muddy freshwater that expands from the Mississippi River into the Gulf off Louisiana. This plume could be a barrier for coastal species trying to expand their range. However, the spreadfin skate is reported to be an outer continental shelf species and may not be influenced by this lower salinity water. So, what is their story?
And why are these not found in the Caribbean? In the Caribbean you do enter tropical waters where coral reefs become more common. There is certainly a species shift when you reach this zone and it could be the food needed by these skates is not found here – a biological barrier. Many find these biogeographic situations interesting.
There are 12 species that have the typical “Carolina marine fish” distribution, which means they are found throughout the Gulf up the eastern seaboard to Massachusetts and south to Brazil. Two, the Atlantic torpedo ray and the roughtail stingray, expand their range farther into Canada. As a matter of fact, the roughtail stingray prefers colder waters.
Torpedo rays are an interesting group. This family of fish includes two species here in the Gulf, the Atlantic torpedo ray and the lesser electric ray. Yep… these two have special muscle cells that can deliver an electric shock. It is believed this electric current can detect and stun prey as well as repel predators. The voltage is not dangerous but will get your attention.
Three of those “Carolina marine species,” the guitarfish, the lesser electric ray, and the yellow stingray, do not reach Massachusetts. Their distribution ends at North Carolina. You would have to guess water temperature as a barrier here. The warm Gulf stream begins heading east across the Atlantic Ocean off Cape Hatteras towards Europe. They could follow this current to Bermuda, but they have not been reported there. This could be due to depth (pressure), being benthic fish, or food barriers.
There is one family that is tropical, the sawfish. These bizarre dinosaur looking creatures were once common in the estuaries of the Gulf region. They are now rare and protected.
One species of stingray, the Atlantic stingray has been found in the lower reaches of Louisiana rivers. Like bull sharks, salinity may not be a barrier for them.
And then we have our “world travelers”. The manta and eagle rays are found across the globe in tropical waters, and eagle rays are common in temperate parts of the world.
The distribution of our rays is not as universal as sharks. The skates in particular have an interesting distribution pattern. Pensacola lies right at the boundary of the eastern and western Gulf of Mexico, so we find both geographic groups here. Though they may scare many people, rays are fascinating creatures and cool to see.