by Rick O'Connor | Mar 11, 2022
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.
by Rick O'Connor | Nov 4, 2021
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.
by Rick O'Connor | Sep 2, 2021
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.
by Laura Tiu | Jun 23, 2021
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.
by Rick O'Connor | Jun 18, 2021
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.
by Rick O'Connor | Jun 3, 2021
With this article we are going to begin a short series on the biogeography of panhandle vertebrates. Biogeography is the study of distribution of life and why species are found where they are. Many are interested in what species are found in a specific location, such as which sharks are found in our area, but understanding why others are not is as interesting.
The Bull Shark is considered one of the more dangerous sharks in the Gulf. This fish can enter freshwater but rarely swims far upstream. Photo: Florida Sea Grant
All species have a point of origin and from there they disperse across the landscape, or ocean, until they reach a barrier that stops that dispersal. These barriers can be something physical, like a mountain range, something climatic, like the average temperature, or something biological, like to abundance of a specific food or predator. There are a lot of barriers that impede dispersal and explain why some species are not present in some locations.
Sharks are marine fish. In general, there is little to impede the dispersal of marine fish. All oceans are connected and there is no reason why a shark found in the Gulf of Mexico could not swim to Australia, and some have. But there are barriers that keep some species of south Florida fish from reaching north Florida – mean water temperature being one.
There are 24 species of sharks from nine different families found in the Gulf of Mexico. Most have a wide distribution range, and some are found worldwide. Nurse sharks are more tropical, common in the Keys, but are found in our area of the northern Gulf of Mexico. They are fans of structure and are often found near our artificial reefs.
Whale sharks and hammerheads are circumtropical, meaning they are restricted by water temperature but found worldwide in warmer waters. Whale sharks are the largest of all fish, reaching a mean length of 45 feet, and are not common near shore. They are plankton feeders and, though large, are harmless to humans. There are five species of hammerheads found in the Gulf of Mexico. They are easily identified by their “hammer” shaped head and are known for their large dorsal fin that, at times, will extend above the surface while they are swimming. Finding species of hammerhead inside the bay is not uncommon.
Several of our local sharks are not as restricted by water temperature and are found as far north as Canada. Sand tigers, threshers, and dogfish seem to prefer the cooler waters and, though found in the Gulf, are not common. There are two members of the mackerel shark family found here. Great whites, of movie fame, prefer cooler waters and are found worldwide – except for polar waters. There are records in the Gulf, but most are offshore in cooler waters. As you know, these are large predatory sharks, reaching up to 25 feet in length, and are known to feed on large prey such as seals. Their cousin the shortfin mako, prefers warmer waters and is more common here. Nearshore encounters with makos is rare but has happened.
The largest family, and best known, are the requiem sharks. There are 13 species in the Gulf, and many are common in our area. Many are not as restricted by water temperature and can be found as far north as New York. Bull sharks are not restricted by salinity and have been found up rivers in Alabama, and Louisiana. Silky sharks are more tropical, and the tiger and spinner sharks are more circumtropical.
The geographic distribution of sharks seems centered on water temperature. Most can easily swim the oceans to locations across the globe but congregate in areas of preferred temperatures and food. Though feared because of attacks on humans, a rare thing actually, they are fascinating animals and world travelers.