As water temperatures rise, Rutgers scientists breed tougher shellfish

Haskin laboratory study may pave the way for climate-change-ready scallops and clams in New Jersey waters
Credit: (Ximing Guo/RU Shellfish Research Laboratory)
Bay scallops are not yet commercially grown in New Jersey, but the Haskin lab’s study suggests they could become a viable species for the state’s shellfish farmers.

Over the last half-century, global sea surface temperatures have been on the rise, but in the last decade they have increased at an accelerated rate.

New Jersey’s coastal waters, both along the Atlantic Coast and Delaware Bay, have been no exception. More alarming, recent research indicates that sea surface temperatures in the Northeast are warming two to three times faster than the global average. For instance, in 2012, water temperatures in the Mid-Atlantic reached the highest levels ever seen in over 150 years of recorded observations.

This rapid increase in water temperature is already influencing New Jersey’s marine species. Breeding habits, ranges and growth rates are adjusting as the environment in which they have evolved to thrive has changed at an unnatural pace. For the commercial fishermen and women whose livelihoods depend on the state’s fishery, particularly those who are only just beginning to experiment with shellfish aquaculture, warmer waters mean higher operational risk.

A new study from the Rutgers University Haskin Shellfish Research Laboratory, which has been monitoring New Jersey’s shellfish stocks for more than a century, is working to combat the impacts of climate change by selectively breeding bay scallops and surf clams that can grow faster and tolerate higher water temperatures.

Opportunity to expand shellfish aquaculture

The project, funded by the National Sea Grant program and led by Ximing Guo, a professor in the university’s Department of Marine and Coastal Sciences, reared juvenile — or “seed” — Atlantic surf clams and bay scallops, identifying in each generation those scallops that grew faster, and those clams that tolerated higher water temperatures.

Currently, only hard clams and oysters are commercially cultured in New Jersey, but this study suggests that shellfish farmers may soon be able to introduce these two additional, potentially more resilient, species.

Credit: (Daphne Munroe/RU Haskin Shellfish Research Laboratory)
A field crew samples bay scallops from a partner farm in Barnegat Bay.

“We haven’t made great progress yet, but the process has allowed us to learn a lot more about how to culture [surf clams and bay scallops] in New Jersey,” Guo said. “Once we can standardize the growing method, then we can expect more progress on selective breeding.”

When Guo and his colleagues were finished with the bay scallop seed, they distributed the thumbnail-size animals to about 15 oyster and hard clam farmers operating throughout Barnegat Bay, to see how they would perform outside the study’s parameters.

James DeMarsh, co-owner of the Atlantic County-based Brigantine Oyster Co., was one of the recipients of the scallop seed. “We began in 2016, so we’re pretty new to the bay, and we’re not scientists,” DeMarsh said. “But our scallops grew. They did much better than I thought in terms of mortality.”

Risks of climate change

For bay scallops, the bigger immediate risk from climate change is disease, which may be linked to rising water temperatures, along with other changes to water chemistry. For Atlantic surf clams, warmer water is the direct threat. Once abundant throughout the state’s barrier island surf zones and other intertidal areas, the surf clam’s range has recently shifted further offshore, to deeper, cooler water.

“It’s critical that we also breed for disease and stress tolerance in order to make the shellfish aquaculture industry more resilient,” said Guo.

Guo also noted that the Port Norris-based Haskin lab recently gave bay scallops to Delaware Bay shellfish farmers, who were able to grow them with some success. Guo is cautiously optimistic. “Obviously, they are able to survive,” he said. “But the data is not conclusive, and we want to know whether they can be grown in the Delaware Bay.”

The early positive results may be minimal, but they represent the important role science will play in the aquaculture industry as the impacts of climate change broaden and intensify.

“The research into on-the-ground solutions for the industry is very important,” said New Jersey Department of Agriculture secretary, Douglas Fisher, “as there are potential impacts to growing conditions and species survival with changing climatic conditions.”

New Jersey’s role in growth of aquaculture sector

Aquaculture is one of the state’s fastest growing food-producing sectors. A decade ago, there were about 30 total aquaculture operations in New Jersey. Today, there are 60 shellfish farms alone. According to the United Nations, aquaculture is expected to grow globally, through 2030. “We continue to plan to position New Jersey to be a part of that growth,” Fisher said.

Expanding and diversifying New Jersey’s shellfish farms doesn’t just promise more dollars for the economy, it offers holistic solutions for historic problems in the state’s shallow nearshore waters, particularly for dealing with excess nitrogen and other nutrients in the water.

“Shellfish aquaculture has value well beyond dollars across the docks,” said Daphne Munroe, Guo’s co-investigator on the study. “Shellfish on farms live out their life just like any other wild shellfish would, and in doing so provide a number of ecosystem services, including providing habitat for other fish and invertebrates and helping to clean water by filtration.”

Credit: Nicole Deck
An example of the relative growth of a bay scallop over the course of a year on a partner farm.

Bay scallops and clams particularly like eelgrass, a long, rigid seaweed whose flat blade is the perfect structure for seed to adhere to. “The effect it could have on the bay is huge,” said Dale Parsons, who farms clams and oysters in Barnegat Bay and is one of the Haskin lab’s partners. “The blades of grass would slow down tidal flow and settle turbidity and improve water clarity. There are areas of vacant bottom where eelgrass could spread like a field.”

More vegetation on the seabed means more marine life, and more of both means a healthier, cleaner aquatic ecosystem. “Shellfish aquaculture is a green industry,” said Guo. “It helps the environment, and also provides high-quality protein for consumers.”

For new farmers like DeMarsh, navigating the uniquely uncertain future of his chosen field feels a little less scary with scientists like Guo working on his side. “It’s important to be connected to the Haskin lab, and for them to keep communicating with us and trying things with us,” he said. “There’s so few of us doing this, so it makes you feel a little less alone.”

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