Pacific geoducks, among the largest burrowing clams in the world, are native to the Pacific Northwest. In recent years, there has been a resurgence of interest in these long-necked clams, partly due to increased demand from Asian markets. Commercially grown only since 1995, farmed geoducks now generate over $20 million in annual sales in Washington State and are among the most valuable farmed shellfish on a per-acre basis. However, hatcheries can be a critical production bottleneck.
“The geoduck aquaculture industry is dependent on seed produced by hatcheries generally from wild broodstock,” said Washington Sea Grant Sustainable Aquaculture Specialist Brent Vadopalas. Broodstock refers to adult animals that are used for breeding purposes. “There are so many steps along the way where things can go wrong as hatcheries struggle to meet production demands.”
A research group composed of Vadopalas, SAFS Professor Steven Roberts, and partners from the University of Rhode Island, Jamestown S’Klallam Tribe, and Baywater Shellfish is focused on improving the aquaculture of geoducks. The group’s primary goal is to test and implement hatchery performance-enhancement methods through the use of environmental preconditioning, or “hardening.”
“It’s akin to climbing Mount Rainier and doing some training ahead of time to condition yourself,” said Vadopalas.
The researchers are specifically looking to identify key stages in the geoduck life cycle when the environmental preconditioning can be applied for optimal benefits to productivity, including broodstock conditioning and reproductive performance, larval growth and survival, and juvenile resistance to stress through repeated exposures. They are also using genomics, epigenomics, and organismal indicators to identify underlying physiological mechanisms involved in enhanced performance, potentially improving hatchery performance in geoducks and other species of shellfish.
Their work builds upon the group’s previous finding that some early exposure to non-lethal low pH conditions can improve larval and juvenile performance. The potential to tolerate acidic conditions may bode well for geoducks’ adaptability to ocean acidification and climate change. These early findings are currently being tested in a commercial shellfish hatchery setting and will determine the genetic and epigenetic markers associated with improved performance.
“In any aquaculture scenario, especially in a hatchery, the grower is trying to enhance larvae or juvenile survival by creating the ‘cushiest’ conditions possible. What we’re exploring is whether making their life slightly less cushy in those early stages is going to give them a leg up on growth and survival later,” said Vadopalas. “From the aquaculture perspective, we’re trying to provide the hatchery operators with a potential tool that they can use to not only ensure survival and growth in the hatchery, but also after juveniles are transplanted into the environment.”
To test for enhanced performance due to prior low pH exposure, geoduck at different life stages were exposed to treated water (ambient pH) or raw water (low pH) in flowing seawater at the Jamestown Point Whitney Ventures, LLC hatchery facility. Researchers are testing performance enhancement in the parental broodstock and their offspring in different stages of development, as well as how low pH treatment of broodstock or larvae enhances larval or juvenile growth and survivorship. They are also testing the effect of repeated low pH exposures on the larvae and juveniles to determine if resistance develops in response to water conditions. Throughout these experiments, researchers are characterizing the geoduck responses at both organismal and molecular levels. Read more