As I write this article it is mid spring, and the rays are bedding on the edges of our seagrass beds. The most common species seen is the Atlantic Stingray (Dasyatis sabina). They are often found in the sandy areas near the grass where they bury in the sand to ambush potential prey. This time of year, their numbers increase as the females are preparing to releasee their young in summer. Mating occurs in early spring and the females will deliver live young1.
According to Hoese and Moore2, there are eight families and 18 species of rays and skates found in the Gulf of Mexico. These are cartilaginous fish found in the same class as sharks but differ in that their gills slits are on the ventral side (bottom) of the body and their pectoral fins begin before the gill slits do on the side of the head. Most are depressed (top to bottom) and appear like pancakes, but not all of them. Sawfish and guitarfish appear more like sharks than rays.
Of the 18 species listed, seven can be found in the estuaries and may be associated with nearby seagrass beds. Two are species of sawfish, which are rare in our bays these days.
The sawfish.
Photo: University of Florida.
There are two members of the eagle ray family, the cownose ray and the eagle ray, which can be found in our bays. These resemble manta rays but differ in that they lack the characteristic “horns” of the manta (often called the Devil Ray because of them) and they do possess a bard on their tail, which manta’s do not. These are more pelagic rays spending their time swimming in the water column and hunting for buried food.
The cownose ray is often mistaken for the manta ray. It lacks the palps (“horns”) found on the manta.
Photo: Florida Sea Grant
The butterfly ray does resemble butterflies in shape having wide “wing-like” fins and a very small tail. It behaves similar to stingrays burying in the sand and ambushing smaller prey.
Two of the more familiar stingrays are found in our grassbeds, the Atlantic Stingray and the Southern Stingray. The Atlantic Stingray’s disk is more round in shape while the Southern Stingray’s is more angular shaped. The Southern Stingray is larger (disk width about five feet, Atlantic disk width is about two feet) and prefers estuaries with higher salinity. The Atlantic Stingray is very common and can tolerate freshwater, thus is common throughout the bay.
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
Stingrays are notorious for their venomous bards and painful stings. They actually try to avoid humans and are frequently spooked by our activity fleeing as soon as they can. However, there are times when people accidentally step on one buried in the sand, or hiding in the grass at which time they will flip their whip-like tail up and over to drive their barb into your foot forcing you to move it – and you do move it – while you yell and scream. The ray then will swim away and can regrow a new barb.
The bard is a modified tooth. It is serrated on each side and there is a thin sac of venom along the flat side of the barb. When it penetrates your foot there is pain enough there. But the natural reaction of your body to an open wound is to close it, this reaction can pop the venom sac and release the toxin. The chemistry of the toxin is not life threatening to humans but is very painful. This experience is something you do want to avoid.
Like their shark cousins, rays do have rows of small teeth which they use to crush small invertebrates including shelled mollusks. They lie in the sand to ambush prey moving in and out of the seagrass beds. They possess two spiracles on the top of their heads which provide water to the gills when they are lying on the seafloor or buried in it.
Like sharks, males can be identified by the two claspers associated with the anal fin and the females usually have two uteri where the young develop. In skates, and some other rays, the young are deposited into the environment within a hardened egg case often called a “mermaids purse”. We see these washed ashore in the beach wrack. Young stingrays usually develop within the female and are born “live” in summer.
Though there is fear of this animal from some seagrass explorers they are a small threat unless you step on one. To avoid this, when in and around the sandy areas of a grassbed, move your feet in what we call the “stingray shuffle”. This is sliding your feet across the surface of the sand instead of stepping. The pressure generated from this movement can be detected by the ray several feet away and they will immediately move away.
Despite the fear, they are amazing creatures and play an important role in the overall health of the grassbed community.
References
1 Snelson, F.F., Williams-Hooper, S.E., Schmid, T.H. 1988. Reproduction and Ecology of the Atlantic Stingray, Dasyatis sabina, in Florida Coastal Lagoons. Copeia. Vol. 1988, No. 3 (Aug 1988). Pp. 729-739.
2 Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M University Presse. College Station TX. Pp. 327.
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.
It is now late May and in recent weeks I, and several volunteers, have been surveying the area for terrapins, horseshoe crabs, and monitoring local seagrass beds. We see many creatures when we are out and about; one that has been quite common all over the bay has been the “stingray”.
The cownose ray is often mistaken for the manta ray. It lacks the palps (“horns”) found on the manta. Photo: Florida Sea Grant
These are intimidating creatures… everyone knows how they can inflict a painful wound using the spine in their tail, but may are not aware that not all “stingrays” can actually use a spine to drive you off – actually, not all “rays” are “stingrays”.
So what is a ray?
First, they are fish – but differ from most fish in that they lack a bony skeleton. Rather it is cartilaginous, which makes them close cousins of the sharks.
So what is the difference between a shark and a ray?
You would immediately jump on the fact that rays are flat disked-shape fish, and that sharks are more tube-shaped and fish like. This is probably true in most cases, but not all. The characteristics that separate the two groups are
The five gill slits of a shark are on the side of the head – they are on the ventral side (underside) of a ray
The pectoral fin begins behind the gill slits in sharks, in front of for the ray group
Not all rays have the whip-like tail that possess a sharp spine; some in fact have a tube-shaped body with a well-developed caudal fin for a tail.
There are eight families and 19 species of rays found in the Gulf of Mexico. Some are not common, but others are very much so.
Sawfish are large tube-shaped rays with a well-developed caudal fin. They are easily recognized by their large rostrum possessing “teeth” giving them their common name. Walking the halls of Sacred Heart Hospital in Pensacola, you will see photos of fishermen posing next to monsters they have captured. Sawfish can reach lengths of 18 feet… truly intimidating. However, they are very slow and lethargic fish. They spend their lives in estuaries, rarely going deeper than 30 feet. They were easy targets for fishermen who displayed them as if they caught a true monster. Today they are difficult to find and are protected. There are still sightings in southwest Florida, and reports from our area, but I have never seen one here. I sure hope to one day. There are two species in the Gulf of Mexico.
Guitarfish are tube-shaped rays that are very elongated. They appear to be sharks, albeit their heads are pretty flat. They more common in the Gulf than the bay and, at times, will congregate near our reefs and fishing piers to breed. They are often confused with the electric rays called torpedo rays, but guitarfish lack the organs needed to deliver an electric shock. They have rounded teeth and prefer crustaceans and mollusk to fish. There is only one species in the Gulf.
Torpedo rays can deliver an electric shock – about 35 volts of one. Though there are stories of these shocking folks to death, I am not aware of any fatalities. Nonetheless, the shock can be serious and beach goers are warned to be cautious. I once mistook one buried in the sand for a shell. Let us just say the jolt got my attention and I may have had a few words for this fish before I returned to the beach. We have two species of torpedo rays in the Gulf of Mexico.
Skates look JUST like stingrays – but they lack the whip-like tail and the venomous spine that goes with it. They are very common in the inshore waters of the Florida Panhandle and though they lack the terrifying spine we are all concerned about, they do possess a series of small thorn-like spine on the back that can be painful to the bare foot of a swimmer. Skates are famous for producing the black egg case folks call the “mermaids’ purse”. These are often found dried up along the shore of both the Gulf and they bay and popular items to take home after a fun day at the beach. There are four species of skates found in the Gulf of Mexico.
Stingrays… this is the one… this is the one we are concerned about. Stingrays can be found on both sides of our barrier islands and like to hide beneath the sand to ambush their prey. More often than not, when we approach they detect this and leave. However, sometimes they will remain in the sand hoping not to be detected. The swimmer then steps on their backs forcing them to whip their long tail over and drive the serrated spine into your foot. This usually makes you move off them – among other things. The piercing is painful and spine (which is actually a modified tooth) possesses glands that contain a toxic substance. It really is no fun to be stung by these guys. Many people will do what is called the “stingray shuffle” as they move through the water. This is basically sliding your feet across the sand reducing your chance of stepping on one. They are no stranger to folks who visit St. Joe Bay. The spines being modified teeth can be easily replaced after lodging in your foot. Actually, it is not uncommon to find one with two or three spines in their tails ready to go. Stingrays do not produce “mermaids’ purses” but rather give live birth. There are five species in the Gulf of Mexico.
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
Butterfly ray is a strange looking fish and easy to recognize. The wide pectoral fins and small tail gives it the appearance of a butterfly. Despite the small tail, it does possess a spine. However, the small tail makes it difficult for the butterfly ray to pierce you with it. There is only one species in the Gulf, the smooth butterfly ray.
Eagle rays are one of the few groups of rays that actually in the middle of the water column instead of sitting on the ocean floor. They can get quite large and often mistaken for manta rays. Eagle rays lack the palps (“horns”) that the manta ray possesses. Rather they have a blunt shaped head and feed on mollusk. They do have venomous spines but, as with the butterfly ray, their tails are too short to extend and use it the way stingrays do. There are two species. The eagle ray is brown and has spots all over its back. The cownose ray is very common and almost every time I see one, I hear “there go manta rays”… again, they are not mantas. They have a habit of swimming in the surf and literally body surfing. Surfers, beachcombers, and fishermen frequently see them.
Last but not least is the very large Manta ray. This large beast can reach 22 feet from wingtip to wing tip. Like eagle rays, they swim through the ocean rather than sit on the bottom. They have to large “horns” (called palps) that help funnel plankton into their mouths. These horns give them one of their common names – the devilfish. Mantas, like eagle and butterfly rays, do have whip-like tails and a venomous spine, but like the above, their tails are much shorter and so effective placement of the spine in your foot is difficult.
Many are concerned when they see rays – thinking that all can inflict a painful spine into your foot – but they are actually really neat animals, and many are very excited to see them.
References
Hoese, H.D., R.H. Moore. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M. College Station, TX. pp. 327.
Shipp, R. L. 2012. Guide to Fishes of the Gulf of Mexico. KME Seabooks. Mobile AL. pp. 250.
