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| Perry Raso, owner of the Matunuck Oyster Farm |
By
ZOE GENTES and ELIZABETH FUTOMA /special to ecoRI.org News
Rhode
Island’s shellfish aquaculture industry has grown tremendously in the past few
years, and is valued at nearly $2 million annually. In fact, more than 4
million oysters were sold for consumption in 2011, according to the state
Coastal Resources Management Council (CRMC).
Despite
advances in fisheries technologies, juvenile mortality in shellfish remains a
problem in many aquaculture programs. One of the biggest challenges for oyster
farmers is disease, which, in the Northeast alone, has caused millions of
dollars in losses in the years that outbreaks occur.
For example, the Northeast oyster industry experienced a decrease in production from a value of $50 million in 1995 to about $15 million in 2005, according to the Food and Agricultural Organization of the United Nations, with a significant portion of that decline attributable to disease outbreak.
Dale
Leavitt, a professor and researcher at Roger Williams University, recently
received funding from Rhode Island Sea Grant to focus on how to help local
shellfish growers improve methods and profits. And, with the support of Rhode
Island Sea Grant, University of Rhode Island researchers are exploring ways to
combat diseases in oyster hatcheries using natural sources.
David
Rowley, associate professor of biomedical and pharmaceutical sciences at URI,
is researching the use of probiotics — live microorganisms beneficial to their
hosts — to prevent outbreaks of disease in hatcheries.
Oyster
larvae are particularly susceptible to bacterial diseases. If a disease
infiltrates a hatchery, it can quickly spread, causing almost immediate
collapse of the population of the oyster larvae being reared.
“The
idea is to create new tools to prevent sporadic mass mortalities,” Rowley said.
“A fascinating discovery has to do with the fact that bacteria communicate with
each other using a chemical language. By doing this, bacteria behave in a
multicellular fashion, including the secretion of toxins or forming biofilms.
This is important in creating infections.”
Rowley’s
team hypothesizes that probiotic bacteria may produce beneficial compounds that
interfere with quorum sensing and thus thwart infectious behaviors. Oysters are
heavily colonized by bacteria, and some of them can provide a beneficial
effect. Probiotics have been used in aquaculture and in other studies as ways
to promote health of cultured organisms.
The
project has already had promising results. “In one case, a bacterium we
isolated from a healthy oyster provides protective effects against infections
if we provide them to healthy larvae,” Rowley said. “We have been studying the
molecular mechanisms involved in that protection. We believe that probiotic
bacteria such as these could become new tools for oyster hatcheries to increase
production and prevent sporadic diseases.”
Rowley
hopes to turn the preliminary discoveries into commercial products to prevent
diseases in oyster larvae. His team will further this plan through work with
the Blount Shellfish Hatchery at Roger Williams University.
Leavitt
said upwellers are one of the most widely used technologies used for shellfish
aquaculture systems. They work by forcing seawater to flow through a bed of
shellfish seed from the bottom to the top instead of the top to the bottom,
according to Leavitt. The end result is better food distribution, so you get
faster and more even growth in the population, he said.
The
goal of this new research is to test various types of flow through an upweller
system to find the optimal water flow pattern.
Both Zoe Gentes and Elizabeth Futoma are communication interns
at Rhode Island Sea Grant. This article originally was published in the Fall
2012 41˚ N.
