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
The leatherback sea turtle is the largest of the five species that have been found in the northern Gulf of Mexico. With a carapace (top shell) length between 6-7 feet and weighing between 800-1000 pounds it is truly a magnificent creature. Any encounter with them is amazing.
Most encounters occur with fishermen or divers who are out searching for artificial reefs to fish or dive. Though very rare, they have been known to nest in this area. They feed exclusively on jellyfish and will follow them close to shore if need be. But what do leatherbacks do with most of their time? Do they hang offshore and follow jellyfish in? Do they circle the entire Gulf of Mexico and we see them as they pass? Based on past studies, many encounters with this turtle occur in the warmer months. They often become entangled in commercial fishing longlines set in the central Gulf of Mexico. But what do they do during the fall and winter? One of the tagging projects presented at a recent workshop tried to answer that question.
The project was led by Dr. Christopher Sasso of the National Oceanic and Atmospheric Administration. The tag chosen for this was a satellite tag. Since the leatherback must surface to breath air, and often is found near the surface following jellyfish, orbiting satellites would be able to follow them. As we mentioned in Part 1, catching the creature is step 1, and catching a six-foot 1000-pound sea turtle is no easy task.
The team used a spotter aircraft to locate the turtles. Once found, the pilot would radio the chase boat who would zip in with a large net. The net was connected to a large metal hoop and was designed to give way once it was around the turtle. Once in the net the turtle was hauled onto a small inflatable boat where the work of tagging could be done. They would measure the animal, take blood samples, place a PIT tag within them (similar to a microchip in your pet) and then attach the satellite tag by a tether to the tail end of the turtle before releasing it. The entire operation took less than 30 minutes.
Between 2015-2019 19 leatherbacks were tagged in the northern Gulf. 17 of these were females and 2 were males. Data obtained from these tags ranged between 63 and 247 days at liberty. The behavior the team noticed was divided into foraging behavior (feeding on jellyfish) and transiting behavior (direct swimming ignoring all).
The turtles foraged in this part of the Gulf until the fall season. At that point most of them moved south along the Florida shelf, past the western peninsula of the state, heading towards the Keys. A few chose to swim directly south against the Loop Current, and a small number remained in the area.
Those moving along the Florida shelf appeared to be foraging as they went. Those crossing the open Gulf may have foraged some but seemed to be focused on getting south to the nesting beaches. Almost all of the turtles entered the Caribbean on the east side of the Yucatan channel, following the currents, with their final destination being their nesting beaches. When they returned, they did so in the warmer months and used the western side of the channel – again following the currents – until they once again reached the northern Gulf and foraging began again. One interesting note from this study, the two males tagged did not leave the Gulf.
The tagging studies do show that leatherbacks use the Gulf of Mexico year-round. They usually head south to the Caribbean when it gets colder and use the currents to do so. It is during the warmer months we are most likely to see them here foraging on jellyfish. It is an amazing experience to encounter one of these large turtles. I hope you get to experience it one day.
Satellite tracks of leatherback movement in the GoM. Red (2015), Blue (2018), Black (2019).
Image: Sasso (et.al.) 2021.
Reference
Sasso, C.R., Richards, P.M., Benson, S.R., Judge, M., Putman, N.F., Snodgrass, D., Stacy, B.A. 2021. Leatherback Sea Turtles in the Eastern Gulf of Mexico: Foraging and Migration Behavior During the Autumn and Winter. Frontiers in Marine Science., Vol. 8., https://doi.org/10.3389/fmars.2021.660798.
Mark Twain once said – “Everyone talks about the weather, but no one does anything about it.” A similar statement could be made about the Gulf Sturgeon – “Everyone talks about the Gulf sturgeon, but on one has actually seen one.” Those along the coast who have a dock, pier, seawall, or have placed a marina, artificial reef, or oyster farm over state submerged lands, have certainly heard about this fish. It is a portion of the permit in each case. Heck, maybe they have seen one. But it is a fish that many know about but seems elusive to encounter.
Left-facing Gulf sturgeon illustration. Lighter brown than Atlantic sturgeon. Credit: Jack Hornady for NOAA Fisheries.
The Gulf sturgeon (Acipenser oxyrinchis desotoi) is one of 27 species of sturgeon found worldwide. It is a subspecies of the Atlantic sturgeon. These are ancient fish, and they look it. Sturgeons are large, reaching lengths of up to eight feet and 300 pounds. They have armored looking scutes embedded into their skin, giving them a “dinosaur” appearance. They have a heterocercal caudal fin that resembles a shark. And like sharks, they have a cartilaginous skeleton and a spiral valve within their digestive tract. Their head has a pointed snout with whisker-like structures called barbels, which are used for detecting food buried in the sand, and they lack teeth. They have been swimming in our oceans since the era of the dinosaurs, about 225 million years.
Sturgeons are anadromous fish, meaning they (like salmon) spend their adult lives in salt water, traveling miles upriver to their location of their birth to lay eggs. The Gulf sturgeon spends the colder months (November through February) inhabiting our bays and the nearshore Gulf of Mexico in waters less than 100 feet. Now is the time when you may encounter one near the coast. Because they eat very little while in the river systems, they gorge on benthic invertebrates during the winter. They spend most of their time over sand flats and sand bars, using their barbels to detect a variety of buried invertebrates. When sturgeon sense warmer months coming, they begin their long migrations up the inland rivers seeking the area where they were born. At this time, they leap from the water like mullet and make splashes that can be heard from a long distance. They are famous for this in the Suwannee River and have, at times, been a concern for boaters and jet skiers. Many boaters have had to go to the hospital due to collisions with leaping sturgeon.
The Gulf Sturgeon.
Photo: U.S. Geological Survey
Once they reach the spawning grounds, if conditions are right – temperature, water flow, and pH – the female will lay between 250,000 – 1,000,000 eggs which will become fertilized by the smaller males. Most eggs will not survive, but for those that do, the cycle will begin again with the trek back towards the Gulf of Mexico beginning in September.
Why are they declining?
Early in the 20th century they were sought after for their meat and fertilized eggs (caviar). Most of the rivers within their range (which is between the Mississippi and Suwannee Rivers) have been damned, dredged, or both. Dams impede their ability to reach their nursery grounds and dredging can reduce the required conditions to stimulate breeding, or literally bury their eggs. Between these human activities, their numbers declined drastically. In 1991 they were listed both as a federally and state threatened species and have been protected and monitored ever since. The best population, and best chance to encounter one, is in the Suwannee River. This river has been left basically pristine and has not had the habitat altering activities of the others. Locally, they are found in the Escambia, Blackwater, and Yellow Rivers.
Winter is the time to see them in the lower parts of our bay. Maybe you will be lucky enough to encounter one.
References
The Gulf Sturgeon. Florida Fish and Wildlife Conservation Commission.
Welcome to Red Snapper Season 2023! The season began June 1, 2023 at 12:01am for “For Hire” vessels fishing in federal waters and continues through August 25, 2023.
For Florida recreational anglers in state waters, the season started a few days later on June 16. While the summer season ends on July 31, 2023, fishing enthusiasts can look forward to 3-day fishing weekends in Florida State waters later in October and November 2023. This means there are still additional days of red snapper fishing opportunities in 2023, giving you ample time to plan exciting fishing adventures.
Here, we present Bay County’s recent artificial reefs, which serve as prime fishing locations for this year’s seasons. This select collection includes three distinct areas: east (State), south (Federal), and west (State). These sites have had the opportunity to grow and mature, with over 290 reef modules deployed between May 2019 and December 2020.
East Location – Sherman Site
Walter Marine deploys one of nine super reefs deployed in Bay County’s NRDA Phase I project located approximately 12 nautical miles southeast of the St. Andrew Pass. Each massive super reef weighs over 36,000 lbs and is 15 ft tall. Multiple modules deployed in tandem provides equivalent tonnage and structure similar to a medium to large sized scuttled vessel. Photo by Bob Cox, Mexico Beach Artificial Reef Association.
This project was completed in May 2019 in partnership with the Mexico Beach Artificial Reef Association, Florida Fish and Wildlife Conservation Commission, and Florida Department of Environmental Protection. The deployment site in the Sherman Artificial Reef Permit Area is approximately 12 nm southeast of St. Andrew Bay Pass at a depth of approximately 80 feet. A total of twenty-five modules were deployed, including nine 18-ton reefs and sixteen 3-ton reefs.
South Location – Large Area Artificial Reef Site (LAARS) A
Large 45,000 lbs. concrete modules staged for deployment. These were placed by HG Harders and Son in July of 2019.
This project was completed in July 2019 in partnership with the Bay County Artificial Reef Association and the Florida Fish and Wildlife Commission. The deployment site in LAARS A is approximately 12 nm south of the pass, with reef modules located around the center of the permitted area. The reefs are situated in about 105 feet of water. There are seventeen reef modules, including five 22-ton reefs with a height of 18 feet and twelve 2.5-ton reefs with a height of 5 feet.
West Location – SAARS E – L
This area has the largest number of reef modules and permit sites. It includes 154 small pyramids that are 8 ft tall and weigh about 10 tons. There are also 26 large pyramids that are 18 ft tall and weigh about 18 tons. Additionally, 25 concrete disk reefs, weighing about 3 tons each, were deployed nested inside select Super Reefs, adding to the complexity and diversity of the reefs. In total, approximately 980 tons of engineered concrete artificial reef material were placed in 8 permitted areas. These deployments were completed in December 2020 with the support of the Mexico Beach Artificial Reef Association.
Bay County’s NRDA Phase II deployment in Small Area Artificial Reef Sites (SAARS) E – L are located 11 – 15 nautical miles (nm) southwest of St Andrew Bay Pass in Florida state waters. (Source ArcGIS mapping software).
This monitoring dive was conducted by FWC in January 2021, shortly after the reefs were deployed. You can move the 360 deg video image to experience what the divers see and observe.
Below is an overview map of these three prime snapper sites!
Wishing everyone great fishing days on the water with family and friends!
Chantille Weber, Coastal Resource Coordinator, UF/IFAS Extension Bay County
L. Scott Jackson, Bay County Extension Director, UF/IFAS Extension Bay County and Florida Sea Grant
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.
The Emerald Coast Open Lionfish Tournament May 20-21, 2023, at HarborWalk Village in Destin, FL, is gearing up to tackle a pressing ecological challenge while showcasing the power of sport to make a positive impact. This unique tournament, held along the picturesque shores of the Emerald Coast, focuses on combating the invasive lionfish population in the region’s waters.
Lionfish, native to the Indo-Pacific region, have become a significant threat to the delicate balance of marine ecosystems in the Gulf of Mexico. With their voracious appetite and rapid reproduction, these invasive species pose a grave danger to native marine life. The Emerald Coast Open Lionfish Tournament aims to address this issue by encouraging divers and fishermen to actively hunt and remove lionfish from the waters.
Participants in the tournament will compete to catch the most lionfish, utilizing their skills in underwater navigation, spearfishing, and conservation. Sponsors provide cash and prizes for multiple categories including most caught, largest and smallest lionfish. The event provides an exciting platform for experienced divers and newcomers alike to contribute to the preservation of the marine environment.
Beyond the ecological significance, the tournament also offers a thrilling experience for both participants and spectators. Divers equipped with their spears dive into the depths, searching for lionfish while showcasing their prowess and bravery. The tournament fosters a sense of camaraderie and shared purpose among the participants, creating a community dedicated to the cause of protecting marine ecosystems.
In addition to the competitive aspect, the Emerald Coast Open Lionfish Tournament promotes education and awareness about the invasive species. Participants and attendees have the opportunity to learn about the impact of lionfish on local marine life and explore sustainable solutions to combat the issue at the free Lionfish Awareness Festival from 10:00-5:00 each day. Sign up to volunteer at the event if you want to join the fun. The week prior to the tournament is dedicated to Lionfish restaurant week where local restaurants practice the “eat ‘um to beat ‘um” philosophy and cook up the tasty fish using a variety of innovative recipes.
The Emerald Coast Open Lionfish Tournament 2023 represents a unique fusion of sport, environmental conservation, and community engagement. By bringing together individuals passionate about marine conservation, this event serves as a powerful catalyst for change and a shining example of how sport can contribute to the preservation of our natural world. Learn more at https://emeraldcoastopen.com.
A Lionfish Removal and Awareness Day festival volunteer sorts lionfish for weighing. (L. Tiu)
