Even though oysters have a hard shell that even humans have a hard time opening, they do have natural predators in our waters that can easily slurp up a couple dozen. Your usual oyster slurping suspects include oyster drills, blue crabs, and fish (such as the black drum). In this article, we will focus on the 3 major predators that contribute the most toward natural mortality in oysters here in the Florida Panhandle.
The Oyster Drill
When it comes to the marine snail world, oyster drills would win an oyster-eating contest. Oyster drills (Urosalpinx cinerea) are marine gastropods that grow to sizes of 0.5 – 1 inch. Oyster drills can be found all along the Atlantic coast of North America and the Gulf of Mexico, and they have been accidentally introduced into Northern Europe and the West Coast of North America. These small but mighty snails have become specialized in consuming oysters. Using chemotaxis, they locate their prey oyster. Once they find it, they secrete an enzyme to soften a portion of the oyster shell. Once softened, they drill into the shell and siphon out oyster meat. Oyster drills have been known to occur in great numbers when the environmental conditions are prime and can wipe out not only entire oyster beds but also clam beds. Oyster drills do have natural predators as well, but these predators also consume oysters.
An Oyster Drill (Urosalpinx cinerea) – Barnegat Bay Shellfish
The Blue Crab
Most of us know about the very tasty blue crab (Callinectes sapidus), but many do not know that it is a major consumer of oysters, especially on an oyster farm. Blue crabs are a decapod crab (meaning 10 legs) of the swimming crab family Portunidae. Blue crabs can indeed swim and their last leg on each side has developed into what are called paddle fins. Juvenile oysters are the main target for blue crabs, but they have been observed eating adult oysters when given the opportunity. On an oyster farm, blue crabs can get into an oyster bag when they are very small. Once inside, they have an all-you-can-eat buffet of oysters, and can quickly wipe out a bag of oysters. Oyster farmers have to be very cautious and must either remove the blue crabs manually or dry their bags out in hopes of destroying any blue crabs. Blue crabs can easily break open a juvenile oyster, but for them to consume an adult oyster, they will wait for it to open to feed before shoving a claw inside of the shell to keep the oyster open. Once they have their claw in the shell, they will use their other claw to consume the oyster.
Blue Crabs (Callinectes sapidus) Pulled Out Of Oyster Bags – Thomas Derbes II
The Fish
Even though oyster-eating fish like black drum (Pogonias cromis) and sheepshead (Archosargus probatocephalus) are much bigger than snails and crabs, they tend to contribute less to oyster mortality on oyster farms. However, during certain seasons wild oysters and other shelled invertebrates can contribute up to 33% of a black drum’s diet (more here). Fish will usually congregate around oyster beds and farms, but they are more interested in consuming oyster predators like crabs and snails. The black drum is a fish that was built for oyster consumption. While black drum lack sharp teeth, they have crushing plates in their throat that can crush an oyster shell which allows the drum to eat the oyster meat. Many oyster farmers welcome these fish on their farms as a free source of anti-fouling and predator deterrent (in the form of consumption).
Black Drum (Pogonias cromis) Caught On A Whole Oyster – Thomas Derbes II
There are many more oyster predators, but these are the top 3 in terms of threat and ability to consume/do detriment to oyster beds and farms in the Florida Panhandle. While oyster drills rank up towards the top, crabs and fish can also greatly contribute to natural mortality.
References
Flimlin, G., & F Beal, B. (n.d.). Major Predators of Cultured Shellfish. https://shellfish.ifas.ufl.edu/wp-content/uploads/Major-Predators-of-Cultured-Shellfish.pdf
You might have seen a floating oyster farm while driving over Garcon Point Bridge or along Scenic Highway. Many people know them for the beautiful, tasty oysters they produce, but those farms have a major ecological benefit that many aren’t aware of. First, the oysters in those cages act as a very efficient water filter, filtering upwards of 30 gallons per day. The floating farms also act as an oasis for other marine creatures, from crustaceans to finfish, and can help increase the biodiversity in the area. Oysters are also great at sequestering carbon into their shells. Today, we will go over these ecological benefits and proper etiquette when maneuvering around the farms to enjoy some of the ecological benefits of the oyster farm.
Florida Pompano Caught Off an Oyster Farm – Thomas Derbes II
Besides being tasty, oysters are very well known for their ability to filter massive amounts of water in a single day. Research has shown rates of up to 50 gallons per day in a laboratory setting, but they filter upwards of 30 gallons per day in the wild. With most oyster farms in the area having more than 500,000 oysters on their farm, that’s more than 15,000,000 gallons of water per day per farm! Oysters can filter out any excess sediments from the water, forming them into small packets and depositing the sediment on the bottom of the bay, keeping the sediments from being re-suspended. This is very beneficial to any bay or estuary as eutrophication (More Here on Eutrophication) has been an issue in almost every bay in the southern United States.
Another benefit to oyster farms is that it is a floating oasis for all types of marine creatures. Blue crabs and stone crabs are a common threat to oysters, and they love to congregate around oyster farms waiting for an easy meal from a dropped oyster or oyster spat on cages. Common bay fish, like the Spotted Seatrout, Sheepshead, and Red Drum, have been known to hang out under the cages consuming smaller finfish and crabs, but some uncommon fish like Tripletail and Florida Pompano also patrol the cages looking for a meal. Because of its ability to hold all types of fish, fishermen love to fish around the oyster farms. Fishing around oyster farms is allowed, but most farmers want the boats to stay on the boundary of the farm and not inside of it. This is due to there being lines under the surface of the water that could potentially damage any lower unit and can cut free a line of cages. Also, it is against state law to be within the boundary of the farm if you are not an authorized harvester of that lease, and I have personally seen FWC enforce those rules. As a seasoned oyster farmer once told me “We know our farm holds fish and it is okay for them to fish the farm, heck put out some blue crab traps around it, but do not mess with the cages and stay outside of the boundary and we can all live in harmony.”
Tripletail Caught Off An Oyster Farm – Brandon Smith
Last but not least is the ability of oysters to sequester carbon and excess nitrogen into their shells and pseudofaeces (aka bio-deposits). Carbon and nitrogen sequestration is a crucial service provided by oysters that helps battle global climate change. Just as they do with excess sediments, they deposit excess carbon and nitrogen into bio-deposits that accumulate on the bottom, keeping them from being re-suspended into the waters. Oyster reefs are currently on the decline around the world, and their decline has “resulted in a forfeiture of several ecosystem services” including carbon and nitrogen sequestration and water filtration. (More Here on Carbon Sequestration)
While oysters might be tasty, we have learned about some of the ecological services oysters provide to an estuarine environment. From water filtration to increasing biodiversity to carbon/nitrogen sequestration, oysters are a major benefit to any estuary and can help fight climate change and eutrophication. Next time you see an oyster farm or reef, give oysters (and farmers) a little appreciation for their hard work in helping make the world a healthier place!
Pompano?! More like Pompa-YES! Growing up in the Panhandle of Florida, I was exposed to many great fishing seasons and opportunities, from the Cobia (Rachycentron canadum) run in the spring to the “Bull” Red Drum (Sciaenops occelatus) run of the fall, but my absolute favorite season was the Florida Pompano (Trachinotus carolinus) run on the beaches. While I enjoyed being on the boat scouring the beaches with a small bucktail jig, casting at sliver flashes in the cuts of the sandbar, I had my most memorable trips on the beach with a few rods, sand spikes, and a “flea rake.” There were no bad days on the beach (as they say, it’s better than a day in the office), and when you happen upon a honey hole, it makes for an incredible day with very little effort and usually an incredible dinner to follow. Since we are rapidly approaching peak pompano season, I will pay homage to the “Silver Surfers of the Emerald Coast” with a little overview of the life of a Florida Pompano.
Beach Fishing for Florida Pompano is for Everyone, Young and Old – Thomas Derbes II
Florida Pompano have a very wide range, from Massachusetts to Brazil, and are a member of the family Carangidae (aka the Jack Family). It is a very popular sport and commercial fishery, and its rapid growth rate makes it a prime candidate for aquaculture. Florida Pompano are highly migratory fish, and they can run from the Florida Keys all the way to Texas and back in a season. In the Florida Panhandle, the Florida Pompano run starts in April/May lasting until July, with a bonus fall run in October/November when they are returning south. When fishing off the sandy beaches of the Florida Panhandle, you can run into its cousins the Permit (Trachinotus falcatus) and Palometa (Trachinotus goodei) who often get mistaken for a Florida Pompano. Another thing they have in common with Florida Pompano is their love of crustaceans including the Mole Crab (aka Sand Fleas) (Emerita portoricensis) and Atlantic White Shrimp (Litopenaeus setiferus).
Just like most members of the family Carangidae, Florida Pompano are considered “batch spawners.” A batch spawner is when a female releases her eggs into the water column and a male simultaneously releases his sperm into the water column. Female Florida Pompano can release upwards of 800,000 eggs per spawning season, and Florida Pompano typically head offshore in early spring to October in the Gulf of Mexico to spawn, and their juveniles return to the beach to grow along the shoreline. Florida Pompano can reach an aquaculture harvest size of 12 inches within one year, and males reach maturity in 1 year whereas females mature after 2 to 3 years.
Florida Pompano Eggs 12 Hours Post Fertilization – Thomas Derbes II
When it comes to table fare, Florida Pompano ranks very high on my personal fish list, and many chefs love serving pompano at their restaurants due to the great, mild taste and fillets that are of even thickness. Their diet of crustaceans helps yield a buttery, almost crab flavor and the meat is very flaky and white. There are many preparation techniques for Florida Pompano, from grilled whole to pan-fried, and pompano have even inspired their own cooking technique, “Pompano en Papillote,” or baking pompano in parchment paper.
Beautiful Florida Pompano Caught Off Pensacola Beach, Florida – Thomas Derbes II
When fishing for Florida Pompano off the beach, most anglers employ a large rod (usually a 10ft rod) with a 20lb fluorocarbon double drop loop rig and pyramid weight. The larger rod allows for maximum casting distance from the beach, giving beach anglers a chance to reach behind the first sandbar. Most anglers will bring either fresh dead shrimp or a flea rake with them to catch the prized bait, mole crabs. Pro tip, when casting out the rods, make sure you have a bait close to the shore in the “trough” and not just past the sandbar. (Learn More About Rigging Here!) If you plan to harvest a Florida Pompano, make sure you check your local regulations. In the Florida Panhandle, Florida Pompano must be 11 inches (fork-length) or larger with a daily limit of 6 per angler.
My nephew showing off his prized Florida Pompano – Zach Saway
I hope you have enjoyed this profile for the Florida Pompano. Now is the time to get your rods out of storage and ready to hit the beach!
I am sure everyone has noticed how cold this winter has been. We have had multiple days in the 20’s here in the Florida panhandle, even some snow flurries near Pensacola. I was first told this may happen by a Sea Grant colleague of mine who works with oyster farmers. Six months ago, he said the Farmer’s Almanac mentioned this would be a colder than normal winter. A few weeks later a Master Naturalist mentioned that if it was heavy “mast season” (lots of acorns on the ground) it would be a colder winter. We certainly had a heavy mast season in Pensacola this year, acorns were EVERYWHERE. And here we are. As I type this it is 27°F outside.
Though we do not see snow as often as Colorado, the panhandle does see snow from time to time.
Photo: Rick O’Connor
This past week I was at a Sea Grant meeting. We were discussing this cold and another colleague mentioned that it was an El Nino year. That’s right… it is an El Nino year, and many know that the weather does change when this occurs.
I first heard of the El Nino shortly after receiving my bachelor’s degree. I was teaching at Dauphin Island Sea Lab, and we had a video series on oceanography and one episode discussed it. It explained that commercial fishermen in Peru were the first to notice it over a century ago.
Off Peru’s coast is a large ocean current that originates in the Antarctic, flows north towards the equator passing the west coast of South America along the way. The water is cold and full of life. The Andes Mountains also run north-south along the coast. Cold air at the top of the mountains runs down towards the coast and offshore. As it blows offshore, it “pushes” the surface water of the ocean offshore as well. This generates an upwelling current moving from the ocean floor towards the surface, bringing with it nutrients from the sediments below. This nutrient reach seawater, mixing with the highly oxygenated cold water, and the sun at the surface creates the perfect environment for a plankton bloom, and a large bloom she is. This large bloom attracts many plankton feeding organisms, including the commercially sought after anchovies and sardines. This in turn supports the tuna fishery that comes to feed on the small fish. These are some of the most productive fisheries on the planet.
Based on records kept by Peruvian fishermen, every three to seven years the surface waters would warm, and the fish would go away. It was lean times for them. When it did occur, it would do so around Christmas time. So, the fishermen referred to it as the El Nino – “the child”.
Based on the video episode we showed the students, others began to notice warming along the western Pacific and realized it was a not a local event, but a global one. A high school friend of mine does sound for nature films and one of his first projects was to video the effects of the El Nino on the seal nesting season in California. As in Peru, the cold waters become warm, the bloom slows and the fish go away, with less fish the mother seals have no food so, cannot produce milk for their newborns waiting on the beach. As horrible as it sounds, and was to watch in Mike’s film, the mothers eventually abandon the newborns to starve.
The video we showed at Sea Lab followed marine biologists studying corals along the western coast of Central America. Here the waters were warming as well, warmer than normal, and the corals were stressed and dying. With orbiting satellites now in place oceanographers were able to view this event from space and watch the entire thing unfold. These images showed that during a normal year the western Pacific had cold water along California and much of South America. The waters along western Central America were warm. But during an El Nino year, warm water replaced the cold, particularly near Peru. Scientists were able to connect several events to El Nino seasons. Increases in wildfires in the western US, people were viewing the northern lights at lower latitudes, droughts occurred where it was usually wet, floods occurred where it was usually dry, and during one El Nino season the Atlanta Falcons made it to the NFL playoffs. Weird things were happening.
The obvious question for science is what drives these El Nino events?
It is understood that our weather and climate are driven by ocean currents. The “dry air” everyone talks about in the western US is driven by the cold California Current. Likewise, the “humid air” of the southeastern US is driven by the warm Gulf Stream. If you alter these currents, you alter the weather and climate of the region. How do you alter ocean currents?
Warm water in the eastern Pacific indicates an El Nino season.
Graphic: NOAA
In the 1980s, when I was teaching at Dauphin Island Sea Lab, the video suggested a connection to sunspots on the surface of the sun. At the time, they were not sure whether the increased sunspot activity triggered the El Nino, or whether there was something else going on, but there was a correlation between the two.
One explanation comes from a textbook on oceanography I used when I was teaching marine science during the 1990s1. It explains the event as such…
During “normal years” cold water from the Arctic and Antarctic runs along the western coasts of North and South America – both heading towards the equator. Once there, the earth’ rotation moves this water westward towards Australia and Indonesia, warming the water as it goes.
Apparently, the ocean currents cannot transport and disperse these warm waters effectively once they reach the western Pacific. Thus, warm water begins to build there.
This accumulating warm water seems to reverse the trade winds that normally flow from the eastern Pacific to the western along the equator. This wind reversal occurs between November and April. It mentions that in the late 1990s the cause of this wind reversal was not well understood.
This wind reversal is often followed by the development of twin “super typhoons” (very strong typhoons) north and south of the equator.
The extreme warm water in the western Pacific affects the weather in the region and this “heat mass” expands spatially. During this expansion, the high-pressure system that sits over the eastern Pacific, bringing them the dry air we know California for, weakens. At the same time, the normal low-pressure system over the western Pacific weakens and, in a sense, things are flipped. This atmospheric change is called the Southern Oscillation, and the entire event was termed the El Nino Southern Oscillation (ENSO).
The power of the typhoons moves warm water from the western Pacific across the equator to the America’s. The waters there warm and the historic El Nino occurs. This movement takes several months.
The El Nino will persist for one to two years. When the warm water eventually releases its heat, the waters cool, and normal conditions return. Until the next El Nino forms.
In the 1990s they had already noticed an increase in the frequency of El Ninos (based on old fishermen’s logs). They suggest climate change may be driving this.
During El Nino years weather patterns change globally, as mentioned above. This altering of the weather impacts all sorts of biological processes, as mentioned above.
Often, the “return” of colder water along the western Pacific “overshoots” normal temperatures and the ocean becomes colder than normal. This has been termed the La Nina.
I kind of imagine the whole process like a sloshing pool of water flowing towards one end of the pool, bouncing off and sloshing back to the other. But instead of water “sloshing around” it is temperatures.
But this was 1996. Have scientists learned anymore about this event?
Not much has changed in their explanation, other than we are much better at predicting when they will happen and alert the public so that farmers, fishermen, fire fighters, etc. are prepared. They do seem to be increasing in frequency.
For the 2024 El Nino, which NOAA began alerting the public in the summer of 2023, they are predicting it to continue for several seasons2. There is no doubt that this winter is colder than normal. The Florida panhandle also experienced a drought this past fall. But… during most El Nino years, hurricanes are few in the Gulf of Mexico. We will see, and watch, how the rest of the year rolls out.
Reference
1 Gross, M.G., Gross, E. 1996. Oceanography; A View of Earth. 7th edition. Prentice Hall. Upper Saddle River, New Jersey. Pp 472.
2 El Nino / Southern Oscillation (ENSO) Diagnostic Discussion. Jan 11, 2024. National Weather Service Climate Prediction Center. National Oceanic and Atmospheric Association.
And it’s a good thing! Green gill oysters are prized in the oyster community. In the Carolinas and Northern France, green gill oysters are a seasonal, cherished crop and a product of the saying “You are what you eat!” The phytoplankton, Haslea ostrearia, is the typical culprit, and their distribution is measured by direct observation from plankton tows or the occurrence of green-gilled oysters. The exact distribution is unknown, but there are reports of H. ostrearia throughout the Atlantic, Pacific, and Indian oceans. Haslea ostrearia is a beautiful pennate diatom that contains a water-soluble blue pigment known as marennine (More Here). Marennine’s production is stimulated by long photoperiods, blue light, and high light/low cloud weather. It can also be released into the water and into the flesh of organisms (typically oysters) that consume them.
Fresh out of the water Grayson Bay Oyster with green gills! – Brandon Smith, Grayson Bay Oyster Company
Pensacola Bay, and surrounding areas, had a pretty mild fall in terms of rainfall, and the bays have turned a beautiful green-blue hue as the bays have risen in salinity and phytoplankton typically found in the Gulf of Mexico were able to survive. Brandon Smith, owner of Grayson Bay Oyster Company, was out working his farm January 7th, 2024, and sent a text to me saying “take note of the green gills,” and I was very shocked and happy to see actual, green-gilled oysters in our local waterways. He graciously harvested a few dozen to examine (and let me taste test), and I was able to confirm the presence of green gills in the oysters. After further research on H. ostrearia, it seems as though the pennate diatom made it into our bays and is the culprit of this wonderful surprise.
A local Grayson Bay Oyster displaying green-gills – Thomas Derbes II
When I shucked my graciously donated oysters from Grayson Bay, I was reminiscing on the first time I came across green-gilled oysters. The first batch of green gill oysters I ate came from an oyster farm in North Carolina called N. Sea Oyster Company. Their green-gilled beauties “Divine Pines” were requested by a wedding I was catering for, and I was able to slurp down one to get talking and tasting notes. The seasonal Divine Pines offered a sweet yet salty taste and became one of my favorite out-of-area oysters to serve at events and to personally consume. While beautiful, the green-gilled oysters are usually only found in the fall/winter months. These green-gilled Grayson Bays were very comparable and offered a salty yet very sweet and minerally finish. The H. ostrearia is responsible for not only the green gills, but the sweet tasting notes, and I highly recommend adding any green-gilled oyster to your fall/winter raw bar selection.
References:
Turpin, Vincent & Robert, J-M & Philippe, Goulletquer & Massé, Guillaume & Rosa, Philippe. (2008). Oyster greening by outdoor mass culture of the diatom Haslea ostrearia Simonsen in enriched seawater. Aquaculture Research. 32. 801 – 809.
