Monitoring program central to planned first shellfish farm in U.S. federal waters

By on August 2, 2013

Miles of the coast of southern California, marine life fueled by upwelled, nutrient-rich water grows so thick on the legs of oil rigs that divers occasionally scrape them clean to maintain the structure’s integrity.

Phil Cruver, a “social entrepreneur” with six startup companies to his name, is banking on that oceanic conveyor belt of nutrients to fuel a unique aquaculture venture that he says could ultimately cut into the millions of dollars that the U.S. spends each year to import mussels.

Cruver is the CEO of the Catalina Sea Ranch, what he intends to be a 100-acre oyster and mussel farm anchored 5.5 miles offshore from Huntington Beach and Long Beach. The project has already been granted a provisional permit from the U.S. Army Corps of Engineers and now awaits approval from the California Coastal Commission.

Once approved and constructed, the operation will be the first shellfish farm in U.S. federal waters.

“What I’m doing here in federal waters off California, there is nobody in my rearview mirror,” Cruver said. “So there’s no competition at all.”

Cruver said the offshore waters are ideal for shellfish production because the animals can feed on the naturally abundant phytoplankton and won’t depend on food pellets like farmed finfish. The ranch will produce oysters, which will be housed in suspended cages, and mussels, which will be seeded on 689-foot long lines.

To ensure the program isn’t detrimental to the environment and lives up to water quality standards, he’s recruited a team of experts for the ranch’s “Offshore Mariculture Monitoring Program.”

“I’m an entrepreneur,” Cruver said. “I’m not a scientist. I’m a business guy.”

Leading the program is Dale Kiefer, a professor of biological sciences at the University of Southern California. Kiefer’s expertise is in plankton dynamics and remote satellite sensing of the oceans, but has turned to aquaculture and fisheries issues in the past five years.

Among the first monitoring efforts at the future site of the ranch was a survey of the sea bottom, which regulators wanted to make sure was free of rocky formations. Those would make for good fish habitat that could be disturbed by the farm’s anchor system. The work, which included multibeam bathymetric and side-scan sonar survey, found the 100-acre area was rock free and dominated by hard-packed sand and mud.

The shellfish farm will be anchored 5.5 miles out on the San Pedro Shelf, marked by the yellow point (Credit: Catalina Sea Ranch)

The preliminary monitoring also included a survey of the benthos conducted through a series of grab samples that were tested for organic carbon levels, macroinvertebrate populations, sediment grain size and heavy metal concentrations. The tests didn’t find anything out of the ordinary and will provide a baseline dataset in later years to determine whether the operations are having an impact on the benthic conditions.

The ranch’s monitoring program hasn’t yet surveyed the water quality in the column, Kiefer said, because this part of the ocean has been consistently well studied. Research on the effects of a sewage treatment plant with an outfall pipe in the area has lead to a long time series of information on water quality.

“It’s probably one of the most heavily sampled coastal areas in the world,” he said. “So we know chlorophyll concentrations, we know water temperature, oxygen concentrations. There are simulation models of current velocity and there is lots of satellite imagery.”

But once the ranch is up and running, instruments will continuously record water quality data.

“We’ll have a fluorometer and water temperature, salinity and dissolved oxygen probes built right into the long-line support system,” he said.

The monitoring program will couple real-time data with simulations from a software program called AquaModel, which predicts the effects of aquaculture operations on benthic conditions and water quality. The model, which Kiefer co-developed, is calibrated to each fish farm it simulates with data on variables including current velocity, the number of fish, growth rates, oxygen consumption and feed rates, among others. Once those numbers are plugged in, the model projects including the deposition of organic carbon below the farm.

The shellfish, which consume oxygen and excrete nitrogen-enriched material, will also create a plume of oxygen-depleted and nutrient-enriched water. The model, which runs in a GIS program, will project the shape and intensity of the plume.

Though the shellfish will use up some oxygen and produce nutrients, Kiefer said the animals are relatively benign compared with a traditional fish farm. That’s especially the case because the shellfish feed on naturally occurring phytoplankton rather than artificial food pellets fed to fish.

“Of course, everything is relative, but they’ll probably be a source of water quality improvement,” he said.

That could be good news for the waters over the San Pedro Shelf. But it’s also good news for Cruver, the “business guy.”

“You save 60 percent of your operating costs because you don’t have to feed these babies,” Cruver said. “You put them out there and they consume the phytoplankton naturally.”

Top image: An illustration of the proposed Catalina Sea Ranch shellfish farm (Credit: Catalina Sea Ranch)

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