This is an amazing animal – the horseshoe crab (Limulus polyphemus). A relic of an age before the dinosaurs, they have been plowing the sediments of our marine and estuarine waters for over 400 million years.
They are thick armored tanks, shaped like horseshoes with a long spikey tail giving them appearance of a stingray. They are usually a deep green color, though some have a brownish hue, and have two lighter colored eyes on each side of the head, though there is a third you cannot see. They crawl across the bottom of the Gulf and bays seeking smaller invertebrates to eat. Their armor protects them from most predators, but they do have a few, like the loggerhead sea turtle. Though harmless to people, they don’t appear that way with numerous spines running along their abdomen and the long spine extending from the rear on a ball and socket joint that allows them to swing it, albeit slowly, in circles. They are pretty cool actually.
They are actually not crabs. They are in the Phylum Arthropoda, like crabs, but not in the Subphylum Crustacea, as crabs are. Rather they are in the Subphylum Chelicerata and more closely related to the arachnids like spiders and scorpions. There are four species of these creatures remaining on the planet, three of those live in Asia, one along the Atlantic and Gulf coast of the United States.
Horseshoe crabs vary in size throughout their range but are typically between one to two feet in length and up to one foot across the head. This would be the size of a large female; males are much smaller.
They are benthic creatures exploring the bottom of both the bays and the open oceans searching for food.
Life for a horseshoe crab begins on the shore. Mom buries her eggs in the sand at the tideline during the spring high tide of either the spring or fall season. They young emerge between two and four weeks and begin life as plankton (though they resemble the adults at this stage). They eventually settle out as juveniles in the seagrasses near where they were born and begin their life as benthic creatures. The large adults eventually work their way out into the open ocean to feed before returning to start the cycle over.
When the females return, smaller males pursue her to shore in hopes of being the one to fertilize her eggs. Many times, a male will use a modified claw that resembles a hook to grab on to the back of the female and ride in with her. But several other males, called satellites, will continue across the bottom in pursuit. Once on the beach she will begin to deposit her eggs in the sand at high tide and the males rush in to fertilize. Studies show that more often than not it is one of the satellites who is successful. And so, it goes over their 20 year life span, and this has been going on for hundreds of millions of years.
Their range extends from the Gulf of Maine to the Gulf of Mexico. Populations within this range have declined in recent years and there have been efforts throughout to manage this problem. Here in Florida the Florida Fish and Wildlife Conservation Commission (FWC) has developed a citizen science project they call The Florida Horseshoe Crab Watch where volunteers visit nesting beaches to collect information from the animals and tag them. Here in Pensacola Bay, though we have seen horseshoe crabs, we have not identified any nesting beaches and that is the focus of our Pensacola Bay Horseshoe Crab Hunt… to find those nesting beaches.
In 2017 we began marking horseshoe crab sightings in the Pensacola Bay area on a map. The purpose of this was to determine if there were “hotspots” (locations that had repeated sightings) that we could use to search for nesting locations. Beginning in 2020 we trained citizen science volunteers to survey one of nine such hotspot locations. Each of these were laid out with beach walking transects that ranged from 0.30 to 0.95 miles in length (mean = 0.69 miles).
In 2022 we trained 14 volunteers in March to survey these transects. They were instructed to visit one of the nine locations ± 30 minutes of spring high tide during the spring months (April-June). All of the spring tides were provided to them, but they had to use an outside resource to determine what time high tide as their location. Each volunteer was provided an FWC data sheet to complete after each survey and submit these to the local Sea Grant Extension Agent.
12 of the 14 volunteers (86%) did conduct at least one survey. These surveys covered six of the nine transect locations (67%) and others surveyed nine new locations.
A total of 77 surveys were conducted during the spring of 2022 for a total of 23.7 miles and logging 77 hours. No horseshoe crabs were sighted, and no nesting beaches were found.
That said, the general public continued to call in sighting reports outside of the official surveys. Six residents sent the Sea Grant Extension Agent records of sightings at six locations around the bay area. Three of these were locations were transect locations we are currently surveying, further confirming these are good places to search. Those three were Big Sabine, Little Sabine, and Sharp Point on Pensacola Beach. The other three locations included Portofino and the point at Ft. Pickens on Pensacola Beach as well as Navarre Beach.
Locations that were surveyed and no sightings were reported included Park West and Morgan Park on Pensacola Beach, Naval Live Oaks in Gulf Breeze, Sanders Beach and Bayou Grande in Pensacola, and Galvez Landing, Perdido Key State Park, Big Lagoon State Park and Tarkiln Bayou out near Perdido Key.
We will continue to search these sites each year in hopes of finding nesting horseshoe crabs. We encourage everyone to continue to report sightings to the Sea Grant Extension Agent in Escambia County (850-475-5230; firstname.lastname@example.org ) and consider becoming a volunteer in the spring.
“Bluefish!” … “It’s just a school of bluefish!” So yelled the lifeguard in Jaws II when Chief Brody had mistaken a school of bluefish for the rogue great white shark that was plaguing the town. He would not have been the first to mistake these large schools for a larger fish, particularly a predatory shark, but as some know, bluefish are quite predatory themselves.
Bluefish Image: University of South Florida
Growing up along the Florida panhandle we heard little about this species. We had heard stories of large bluefish schooling along the Atlantic coast killing prey with their razor-sharp teeth and, at times, biting humans. But not much was mentioned about them swimming along our shores. But they do, and I have caught some.
Bluefish are one of several in a group Hoese and Moore refer to as “mackerel-like fish” in Fishes of the Gulf of Mexico. They differ in that they lack the finlets found along the dorsal and ventral sides of the mackerel body and mackerels lack scales having a smoother skin. Bluefish are the only members of the family Pomatomidae. They can reach three feet in length and up to 30 pounds. They travel in large schools viciously feeding on just about anything they can catch and seem to really like menhaden. They move inshore for feeding and protection from larger ocean predators but do move offshore for breeding.
Bluefish landed from the Gulf of Mexico are much smaller than their Atlantic cousins, rarely weighing in more than three pounds. They do have a deep blue-green color to them and thin caudal peduncle and forked tail giving them the resemblance of a mackerel or jack. Some say they are bit too oily to eat while others enjoy them quite a bit. There is a commercial fishery for them in Florida and, as you would expect, it is a larger fishery along the east coast. Most of the panhandle counties have had commercial landings, albeit small ones.
Biogeographically, the blue fish are found all along the Atlantic seaboard and into the Gulf of Mexico. It is listed as worldwide but seems to be absent from the Caribbean and other tropical seas. This could be due to a distaste of warmer waters, or the lack of their prey targets.
They are an interesting and less known fish in our region. Swimming in a school of them should be done with caution, there are reports of nips and bites from these voracious predators.
This began with a call from one of my volunteers who was checking salinity at Shoreline Park. She reported the salinity, but also reported to smell of dead fish – though she could not see them. I visited Shoreline Park the following day on another project and could smell it as well. There was a large amount of dead seagrass washed ashore from a recent storm and I thought this may be the cause of the smell because I did not see the dead fish either.
When I got home, I checked the FWC fish kill database. It reported a redfish kill in Pensacola Bay. It is unusual to see a kill of only one species. Many times, these are releases from fishing activity, particularly bait, and thought this must be the case – FWC did not mention the cause. I let the volunteer know and asked to keep an eye out.
I reported this to the Escambia County Division of Marine Resources to (a) let them know, and (b) to find out if they had any idea of cause. They replied that the location was incorrect. The kill was actually near Galvez Landing on Innerarity Point. He (Robert Turpin) had visited the site and did find any dead fish. I have a lot of volunteers over that way so asked each to take a look. They did not see any dead fish. I asked them to keep an eye out and collect a dead fish if they saw one for testing. Often when a large fish kill occurs, and it is only one species, the suspect cause is disease. Tissue samples could confirm this.
And then came another call.
This time it was from one of our Master Naturalist who lives on the eastern shore of Mobile Bay. He wanted to know what was up with all of the dead redfish along the shore of the bay. He sent photos and his beach was littered with them. I reached out to Mississippi/Alabama Sea Grant to see if they knew what was going on. They had heard about the situation and knew the Alabama Department of Natural Resources was collecting samples. The Gulf Islands National Seashore then reported large numbers of dead redfish along the National Shores property in Mississippi, something was up.
Dead redfish on the eastern shore of Mobile Bay. Photo: Jimbo Meador
I eventually got word from Dr. Marcus Drymon at the Dauphin Island Sea Lab. They had a team working on this. Their team reported that stratification of the Gulf had created a hypoxic (low dissolved oxygen) layer on the bottom and the male “bull redfish” had gathered for breeding and died.
So, we are back to our title – what is stratification and how did this cause the fish kill?
Stratification is the layering of the water. Less dense water will sit atop the more dense. Water temperature or salinity can cause this density difference and layering. Colder and/or saltier water is denser and will form the bottom layer. If you have high winds, it will mix the water and the stratification disappears. Tides and currents can affect this as well.
What they believe happened recently was excessive amounts of rainfall created a large layer of freshwater to move from Mobile Bay into the open Gulf. The combination of tides and wind allowed a stratified layer to form. The oxygen that marine life uses is dissolved into the water at the surface and referred to as dissolved oxygen (DO). If the system is stratified, then the oxygen dissolved at the surface will not reach the bottom and hypoxia (low DO) can happen. They this is what happen. It just so happens that the large male redfish (bull reds) had congregated just offshore for breeding. They are more sensitive to low DO than the smaller females and any juveniles. So, the males died. To answer the question as to why other fish did not die (what you typically see in a DO related fish kill) – the numbers were not mentioned by there was one reference to 4.0 ppm. This is the high threshold of hypoxia. Many fish can tolerate at this concentration, but the male redfish could not.
So, that is what we think happened. The perfect storm of the demise of a group of male redfish just off of Mobile, and the carcasses drifted to other locations.
Do you live in Bay, Gulf, and Franklin County? We need your help! Scallop Sitters is one of our cooperative volunteer programs with Florida Fish and Wildlife (FWC).
Historically, populations of bay scallops were in large numbers and able to support fisheries across many North Florida bays, including St Andrew Bay, St Joe Bay, and Alligator Harbor (Franklin County). Consecutive years of poor environmental conditions, habitat loss, and general “bad luck” resulted in poor annual production and caused the scallop fishery to close. Bay scallops are a short-lived species growing from babies to spawning adults and dying in about a year. Scallop populations can recover quickly when growing conditions are good and can decline dramatically when growing conditions are bad.
An opportunity to jump start restoration of North Florida’s bay scallops came in 2011. Using funding from the Deepwater Horizon Oil Spill, a multi-county scallop restoration program was proposed and eventually set up in 2016. Scientists with FWC use hatchery reared scallops obtained from parents or broodstock from local bays to grow them in mass to increase the number of spawning adults near critical seagrass habitat.
FWC also created another program where volunteers can help with restoration called “Scallop Sitters” in 2018 and invited UF/IFAS Extension to help manage the volunteer part of the program in 2019 which led to targeted efforts in Gulf and Bay Counties.
Giving scallops a helping hand, “Scallop Sitters” work with UF/IFAS Extension, Florida Sea Grant, and FWC restoration scientists by cleaning scallops and checking salinity once a month from June through January. Photo by Tyler Jones, UF/IFAS Extension and Florida Sea Grant.
After the 2020 hiatus due to COVID-19, the program boasted nearly 100 volunteers for the 2021 campaign. UF/IFAS Extension is once again partnering with FWC in Bay and Gulf and Franklin Counties. Despite challenges with rainfall, stormwater runoff, and low salinity, our Scallop Sitter volunteers have supplied valuable information to researchers and restoration efforts, especially in these beginning years of our program. Scallop Sitters collect useful information about salinities throughout the target bays. But the bulk of the impact comes with keeping a close watch on their scallops. The scallops maintained by their sitters have a better chance of a successful spawn when the time is right.
A “Scallop Sitter” cage ready for placement near seagrasses. The cages are restoration tools used to produce baby scallops during the annual growing cycle. Photo by L. Scott Jackson.
So, what does a Scallop Sitter do? Volunteers manage predator exclusion cages of scallops, which are either placed in the bay or by a dock. The cages supply a safe environment for the scallops to live and reproduce, and in turn repopulate the bays. Volunteers make monthly visits from June until January to their assigned cages where they clean scallops removing attached barnacles and other potential problem organisms. Scallop Sitters watch the mortality rate and collect salinity data which helps figure out restoration goals and success in targeted areas.
Bay County: June 16th Kickoff Reception 9:30AM, Pick-up 10:00AM – 1:00 PM (Central)
An Equal Opportunity Institution. UF/IFAS Extension, University of Florida, Institute of Food and Agricultural Sciences, Andra Johnson, Dean for UF/IFAS Extension. Single copies of UF/IFAS Extension publications (excluding 4-H and youth publications) are available free to Florida residents from county UF/IFAS Extension offices.
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.
Gag grouper. 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.