EGH Associate Professor, Dr. Andrew Kane, discusses current research on the oyster population in the Gulf of Mexico

Oysters, as well as other bivalve mollusks, are filter feeders.  They do it all day long, if they’re happy.  In the effort to capture energy from microscopic organisms (such as algae), oysters filter up to 100 gallons of water per day.  Their role in the ecological stability of many estuaries worldwide cannot be understated.  These little seafood items have also been prized for their sweet flavor by those who know and care.

The majority of wild oysters produced in the United States come from the rich waters of the Gulf of Mexico.  And arguably some of the best Gulf oysters are produced right here in Florida – in Apalachicola Bay.

A beaut. Creamy oyster meat fills out a pretty shell. A condition index for the oyster meat is used to discern overall health and potential effects of environmental conditions. The index looks for opaque, creamy to tan meat that fills the cup of the shell.
A beaut. Creamy oyster meat fills out a pretty shell. A condition index for the oyster meat is used to discern overall health and potential effects of environmental conditions. The index looks for opaque, creamy to tan meat that fills the cup of the shell.

The past several years have brought remarkable change to Apalachicola Bay, and to the hundreds of seafood workers who make their living on the Bay.  The chance is not good. While the total harvest of oysters appears to remain stable, each year it is taking more and  more trips by oystermen to collect the same numbers. This situation is typical of what happens before the collapse of a fishery, as fishers work harder and harder, depleting the population down (sometimes to extirpation).

The change in oyster harvest per unit of effort has may be associated with the historical drought in the Apalachicola-Chattahoochee-Flint watershed that provides freshwater to the Bay.  In addition to drought, the hydrology of the Apalachicola River has been altered by withdrawals for urban and agricultural uses and impoundments of sections of the river by dams.  The other climatologically-relevant factor is torrential rainfall.  It takes several dramatic rainfall events each year to be able to move critical nutrients from the watershed into the river system, and into the bay to stimulate phytoplankton growth at the bottom of the food chain. These rainy season pulses of freshwater also are critical to pushing saltwater predators out of the bay that normally live in the Gulf of Mexico (e.g., sponges, crabs, clams and conchs) so they do not heavily affect or consume the oysters. That kind of rainfall hasn’t been seen since 2010.

oyster with spat
Oyster with spat. Can you see the two young oysters growing on this harvest-size oyster? Oyster larvae are motile in the water column until they “settle down” as spat on hard surfaces such as this conspecific oyster. Fouling organisms such as barnacles, sea squirts and sponges deter spat settlement, and can reduce the aesthetics of the shell.

All this, coupled with notable concerns about possible oil spill effects on the bay, has made for mell of a hess.  Hundreds of seafood workers and their families cannot harvest enough oysters to pay their bills and keep their lights on.

Through the leadership of Jack Payne (UF IFAS) and Karl Havens (Florida Sea Grant), a University of Florida Oyster Recovery Team has been assembled with expertise in ecosystem modeling, fisheries management and aquatic animal health.

Some of the animal health work is being lead by Andy Kane, associate professor of environmental and global health, and director of the UF Aquatic Pathobiology Laboratories.  Kane is focusing on ways to better understand the relationship between the higher salinity in the Bay (due to reduced freshwater input) and the presence and intensity of fouling organisms that can grow on oyster shells, and can affect oyster growth and the aesthetics of the shell.

Kane has teamed up with local oystermen to sample oysters throughout Apalachicola Bay.  “Their knowledge of the bay and where the oysters grow best,” says Kane, “is indispensible to implement a biologically meaningful sampling program.”

Initial oyster samples have been analyzed for size, condition index, and salinity-loving fouling organisms.  “We’ve found really high numbers of organisms that drill into the shell of the oysters and weaken them,” said Dr. Kane, “but relatively low numbers of Perkinsus – which is good.”  Perkinsus is the genus name for a microscopic parasite that can devastate oyster populations (but which is not harmful to humans), particularly under high salinity conditions.  Additional data indicates that the current “…methods used to estimate oyster density in the Bay may not accurately account for the uneven distribution of oysters on the different oyster bars, nor the numbers of spat – the baby oysters that settle down and grow to become the oysters we think about harvesting some 6 months to a year later.”

Oyster sampling at sunrise, near Cat Point, one of the more productive oyster bars in Apalachicola Bay. Shannon Hartsfield, president of the Franklin County Seafood Workers Association, assists Dr. Kane with making oyster collections from different areas of the bay, based on salinity gradients.

Kane is also lead investigator on a NIEHS-funded project looking at seafood safety and coastal community health.  In addition to oyster health and growth studies, additional data has been analyzed for oil spill-related contaminants.  Dr. Kane recently presented these initial data at an Apalachicola community meeting, as well as at the Gulf of Mexico Oil Spill and Ecosystem Science Conference.

“So far, our data indicate that Apalachicola Bay oysters are clean relative to the PAHs that can be associated with oil spills,” Kane said.  “These are the same kind of  “all clear” data that were provided by other state and federal agencies.”  When asked if he eats oysters, Andy replied that although he likes…“to eat them raw, a barely-roasted oyster on the barbeque is the best – it just melts in my mouth with that unique Apalachicola sweetness.”

Efforts from Kane and other UF researchers are starting to help the seafood workers back on their feet.  Oyster health and management tools are being developed so that seafood workers, the management agencies responsible for regulating the fishery, and the National Estuarine Research Reserve Service, can work together to manage the healthy, sustainable oyster fishery that Apalachicola Bay has historically supported.  The status of Apalachicola Bay as one of 28 national estuarine research reserves, is based on its ecological importance, relevance, and diversity.  It’s also a beautiful place to visit, take in the sights of a heritage fishery, and enjoy some of Florida’s best seafood.  Bon appetit! *

* As part of a College of Public Health and Health Professions, we’d be remiss not to mention that consuming raw or undercooked meats and seafood, particularly by persons who may be immunocompromised, may increase your risk of foodborne illness.


Kane and Oglaend
Dr. Andy Kane discusses variation in oyster conditions with Ida Øglænd at the UF Aquatic Pathobiology Laboratories. Ida is a visiting graduate student from the University of Stavanger, Norway. She is conducting her thesis research with Dr. Kane on environmental interactions of Perkinsus infections in oysters.