Bright Future for Texas Oysters

Photo by Jerod Foster for The Nature Conservancy

Article by NATE SKINNER

Oysters are interesting creatures, and arguably one of the most unique mollusk species found within Texas estuarine waters. Although most originate as a single animal, they typically grow into consolidated reefs, providing habitat, refuge and food to a plethora of marine aquatic species.

According to Dr. Jennifer Pollack, the Texas A&M UniversityCorpus Christi Harte Research Institute Chair for Coastal Conservation and Restoration, one of the most important impacts that oysters have on our bay systems comes from the fact that they filter the water.

“Healthy oyster reefs contribute to the overall water quality of an estuary,” Pollack said. "Oysters are filter feeders. They use their gills to absorb oxygen, while consuming phytoplankton. This process provides them sustenance, all the while, filtering the water. One oyster will filter up to 50 gallons of water per day.”

Oysters reefs also serve as barriers or buffers and protect adjacent shorelines and marshes from erosion. They typically concentrate prey species for inshore game fish, making the waters surrounding them popular fishing grounds among the recreational angling crowd.

Photo by Jerod Foster for The Nature Conservancy

Pollack said that oysters have long been a bioindicator for changes in freshwater inflows and salinities within Texas bays.

“There are measurable traits and attributes among oyster reefs that reveal how salinities are being impacted,” Pollack said. “These include the average size of harvested oysters, as well as mortality rates and the overall health of specific oyster reefs.”

Pollack said that one of the largest effects that high salinity conditions have on oysters is the increased threat of predators. This typically takes place during drought periods when freshwater inflows into estuaries are very minimal.

“As salinities within an estuary become similar to those found in the Gulf, populations of predators that harm oysters may increase,” Pollack said. “The two main species that threaten oysters are the blue crab and oyster drill.”

The oyster drill is a snail that uses its tongue, or radula, to drill a hole through an oyster’s shell. This enables it to feed upon the bivalve.

“Spat, or juvenile oysters, are typically the most susceptible to predators,” Pollack said. “Their shells are oftentimes much weaker than those of an adult oyster.”

Another threat that oysters face when salinities are high is disease.

“The most common disease found in mature oysters is Dermo,” Pollack said. “It is caused by the protozoan parasite, Perkinsus marinus, and is characterized by the degradation of oyster tissues. Dermo results in massive mortality among oyster populations.” Oysters can contract Dermo from other oysters.

“Perkinsus marinus is transferred into the water column when oysters that were already contaminated with the parasite die from Dermo and decompose,” Pollack said. “Live oysters then become stricken with the disease by ingesting Perkinsus marinus while they are filtering the water. Feces from the parasite in the water column can also cause Dermo among oyster populations.”

Pollack said that Perkinsus marinus thrives in warm, super saline waters. Oyster populations rely on ample freshwater inflows to dilute estuarine water salinity and keep it at levels inhospitable to the disease-causing parasite.

The ideal salinity range for oysters along the Texas coast is somewhere between 10-25 ppt. Pollack said that oysters will undergo osmotic and physical stresses when they experience the extreme ends of the salinity spectrum.

“This becomes especially true when periods of extreme low salinities are experienced,” Pollack said. “Oysters are capable of withstanding short pulses of intense, freshwater inflows; however, they will clam-up, or shut completely, when salinities plunge too rapidly. The problem with this is, that during warm conditions, oysters can only stay shut for short periods of time or they will not survive.”

Oysters have a much faster metabolism in warm water than they do in cold water. They feed more often during the warmer periods of the year by filtering the water that is available.

Photo courtesy of Galveston Bay Foundation

Oysters spawn when water temperatures rise above about 68°F. Spawning continues in intervals, throughout the summer months. Fertilization occurs in open water, and the egg soon develops into a microscopic, free-swimming larvae. This stage lasts about three weeks.

“Chemical cues given off by bacteria and algae growing on hard surfaces appear to trigger the free-swimming larvae to change shape into a small oyster, about the size of a grain of pepper called a spat,” Pollack said. “Spat will attach themselves to many types of hard material or cultch, but they prefer the shells of other mollusks or oysters. Oysters can reach sexual maturity in as little as four weeks after attachment.”

THE TEXAS WILD OYSTER FISHERY

According to the Team Leader for the TPWD Habitat Assessment Team Emma Clarkson, Texas coastal bays are home to approximately 79,000 acres of wild oyster reefs. Of these 79,000 acres, about 76,000 are located within the Aransas, San Antonio, Matagorda and Galveston Bay systems where oysters are commercially harvested.

“In 2020, we had 18 wild oyster dealers and 468 licensed and permitted oyster fishing vessels,” Clarkson said.

In 2019, the ex-vessel value for the wild oyster fishery was approximately $33 million, including both public oyster reefs and private oyster leases. Approximately 5.2 million pounds of oyster meat weight was harvested by the commercial fishery in 2019. The 20-year long term average is approximately $19 million per year for the ex-vessel value, and about 4.6 million pounds of oyster meat weight harvested per year.

The 2020-2021 commercial oyster season was open November 1, 2020 - April 30, 2021. This did not include private leases with TPWD permits, where there is no closed season. During open season, oysters could be harvested Monday through Friday from sunrise to 3:30 p.m.

The current bag limit for commercial oyster harvests is 30 sacks per day. Each sack must weigh no more than 110 pounds, including dead oyster shell and the sack.

In 2017, the Texas Legislature passed House Bill 51, which has helped to preserve the future of our wild oyster fishery. The bill requires entities and purchasers within the commercial oyster industry to replant oyster cultch equivalent to 30 percent of the total amount of oysters that they purchased by volume during the previous license year into areas approved by TPWD. This can be in the form of oyster shells or other TPWD-approved oyster cultch material.

These commercial entities can also choose to pay TPWD a fee that will go toward replanting the material instead of replanting it themselves. This fee is calculated by multiplying the market cost by 30 percent of the volume of oysters that the entity or individual purchased, during the previous license year.

Since the passage of House Bill 51, approximately 40 acres of oyster reef have been restored with over 22,000 cubic yards of cultch.

OYSTER RESTORATION EFFORTS

Oyster restoration projects, as well as plans for future projects, are underway in a variety of locations and bay systems along the Texas coast. These projects have been the effort of a variety of agencies and organizations in partnership with TPWD, and their purpose enhancing the wild oyster fishery across Texas bays, ultimately preserving its future.

According to the Coastal Conservation Association (CCA) Advocacy Director Shane Bonnot, an oyster habitat expansion project was recently completed back in November of 2020 in the southwest portion of Sabine Lake. Funds for this project were provided by the CCA Building Conservation Trust and Harvey Fisheries Disaster Relief funds.

This expansion project included 3,706 cubic yards of oyster cultch in the form of limestone, which produced 926 new mounds of substrate that were strategically placed in relation to already existing oyster reef expansion material. The project's goal was adding a bunch of small patch reefs near natural, existing oyster reefs and previously deployed cultch from prior oyster habitat expansion efforts.

Bonnot said that historically, most oyster cultch has been deployed in a manner in which it was sheeted or spread out evenly and flat across the bay floor.

“TPWD and CCA both agree that the mounding technique utilized in the project mimics the structure of a more natural oyster reef,” said Bonnot. “The mounds were all placed within a rock’s throw of each other."

OYSTER REEF RESTORATION

Photos courtesy of Galveston Bay Foundation

It is anticipated the checkerboard design will promote tremendous expansion of the existing reef in the southwestern portion of Sabine Lake." Sampling since this cultch was deployed in November is already showing that oyster spat are attaching to the new material.

TPWD Coastal Ecologist Bill Rodney said that TPWD recently partnered with The Nature Conservancy and the Galveston Bay Foundation, to complete the Galveston Bay Sustainable Oyster Restoration Project located in Galveston Bay's upper portion.

“This project included a combination of fishable reefs that are available to commercial oyster fishermen, and one sanctuary reef that is not fishable by commercial vessels,” Rodney said.

The reef is about 15 acres in size and is composed of large cultch material. The project's goal is for the reef to become a home for large mature oysters to spawn, ultimately creating a hub for larval production, which will then supplement and further enhance the surrounding, harvestable reefs. The reef is positioned in a way that the predominant direction of tidal flows will distribute oyster larvae to the smaller reefs that surround it.

Rodney said, "Essentially, the should become a larvae factory and will help sustain and replenish the reefs around it, as mature oysters are harvested from them."

According to the Galveston Bay Foundation Habitat Restoration Manager Haille Leija, there is also oyster restoration work taking place in various locales along Galveston Bay in the form of oyster shell recycling.

“The Galveston Bay Foundation’s Oyster Shell Recycling Program focuses on returning shucked oyster shells collected from local restaurants back into Galveston Bay to create new oyster habitat, and to prevent erosion along shorelines,” Leija said. “The program is rapidly growing, and we are getting more and more interest and participation from area restaurants.”

Leija said that the Galveston Bay Foundation is also working with volunteers that own or live on waterfront properties along Galveston Bay to build and grow their own oyster garden using recycled oyster shells. The volunteers, recruited from the communities surrounding Galveston Bay, are educated on oyster biology, usually during a hands-on workshop. They then take some recycled oyster shells home and hang them from their bulkhead, dock or pier in the water using a mariculture-type bag or cage during the spawning season. "The hope is that these oyster gardens grow and thrive, attracting new oyster larvae that is floating around in the water," Leija said. "At the end of the spawning season, we collect the gardens and deploy them at oyster restoration project sites that we have been working on to further enhance their productivity.”

Oyster shell recycling site near Texas City

Photo courtesy of Galveston Bay Foundation

In Aransas Bay, Pollack said that a recently completed TPWD oyster restoration project is already showing signs of growth. This project, designed by TPWD's Emma Clarkson involved developing a reef that was built into many mounds about 1.5 meters tall, surrounded by flats consisting of several inches of cultch placed on the bay bottom.

“The idea is that the tall mounds are more resilient to fishing activity and storm damage, and thus provide longterm habitat for oysters to grow, thrive and produce larvae that will replenish the surrounding reefs,” Clarkson said.

“It’s very similar to the project that took place in upper Galveston Bay,” Pollack said. “We’ve never seen reef growth and expansion take place at this rate. The density of the new growth is impressive, and it’s all taken place in less than a year.”

In the last decade, TPWD has restored over 500 acres of oyster reef in Texas.

OYSTER MARICULTURE IN TEXAS

Oyster mariculture in Texas was created under the Texas Parks and Wildlife Code Chapter 75, by House Bill 1300 from the 86th Legislative Session. It was passed on May 24, 2019, and was later championed by TWA member and Senator Lois Kolkhorst. The bill mandated that the new program be adopted by August 31, 2020. The Texas Parks and Wildlife Commission adopted the program on May 21, 2020, opening the door for Texans to begin farming oysters within our coastal bays.

According to Clarkson several agencies are involved in the oyster mariculture program, including the General Land Office (because oyster farmers will have to lease the bay bottom that they want to use for their farm from them), the Army Corps of Engineers (because oyster farming involves some sort of discharge), the TCEQ, and the Texas Department of Agriculture.

New oyster growth

Photo courtesy of Galveston Bay Foundation

“We really had to work on figuring out the permitting process with the involvement of all of these agencies,” Clarkson said. “A lot of folks look at the program and initially think that TPWD made the permitting process so lengthy and difficult, but it is really just a result of the way the code is written. All of these agencies have jurisdiction over the key components necessary to build an oyster farm, an oyster nursery or an oyster hatchery.”

Clarkson said that TPWD did make an effort to work with the other agencies to find out what applicants will need to do in order to get the necessary permits to begin practicing oyster mariculture.

“Although we cannot supply all of the permits, we can definitely assist and point folks that want to participate in the program in the right direction,” Clarkson said.

The oyster mariculture program is designed to satisfy the demand of the growing half shell market for oysters. While this market may not directly compete with the wild caught oyster fishery, it may serve to help take some pressure off our wild, natural oyster reefs.

“Farmed oysters will be boutique quality, meaning they will be consistent in shape and visually appealing, compared to what you would find on a natural, wild oyster reef,” Clarkson said. “They will have a deeper, cupped shell, and will be perfect for restaurants serving oysters on the half shell.”

Brad Lomax, owner of Water Street Oyster Bar in Corpus Christi, has been working with Clarkson throughout the permitting process to become the first oyster farmer in Texas. He has received the first-ever conditional oyster mariculture permit from TPWD and is now working with the other agencies involved to obtain the rest of the permits necessary to move forward with his oyster farming endeavor.

“Clarkson and TPWD have been great to work with throughout this entire process,” Lomax said.

Lomax’s oyster farm will be located in Copano Bay, about 1,000 feet offshore from Swan Lake. It consists of 8 acres of water, with depths varying from 7-10 feet. The farm’s shorebased headquarters will be stationed about a mile away as a crow flies on the shoreline of Port Bay.

“What oysters do for the marine environment is extremely important for our estuaries,” Lomax said. “I believe that oyster mariculture will be able to take significant pressure off of our wild reefs over the next ten years. I really want to see this new industry grow and thrive.”

TWA Legislative Program Coordinator Joey Park said that from the governmental and regulatory side of things, it is important that the oyster mariculture program continues to evolve in a way that allows others to get into the industry.

“We don’t need it to be too difficult and too expensive to where we are not able to see other Texans willing to take advantage of this mariculture opportunity,” Park said. “At the end of the day, this program can develop a new thriving market and industry within our state, and at the same time, remove some pressure from our natural, wild oyster reefs that are essential to our estuaries.”

Sen. Kolkhorst said that oyster mariculture provides a sustainable way to produce Texas Gulf Coast oysters.

“I am proud of the work we have done to support commercial oyster mariculture in Texas, and I am delighted to continue working on legislation to further help commercial oyster mariculture with Chairman Todd Hunter,” Kolkhorst said.

The future of oysters in Texas looks pretty bright. From thriving oyster restoration to new oyster mariculture opportunities, it will be exciting to see how things continue to evolve for our coastal oyster reefs, both wild and farmed.