Wanda swims lazily in an 8,500-gallon black
plastic tank until she senses the approach of visitors. Then she
breaks the surface of the cold, clear water in a frenzied greeting
exacerbated by the natural orientation of her head, permanently cocked
to one side in the trademark twist of her species.
Far removed from her deepwater ocean haunts, she
is one of more than 100 adult Atlantic halibut being raised as brood
stock at the University of Maine Center for Cooperative Aquaculture
Research (CCAR) in Franklin, Maine. Wanda and her companions supply
the eggs and milt that seed the production lines of CCAR's halibut
aquaculture program, turning a diet of carefully formulated krill,
squid, crab and fish sausages into the next generation of Hippoglossus
hippoglossus.
Wanda weighs in at a hefty 120 pounds, the first
big hint that there are peculiarities of the halibut's life cycle that
make the rules for raising such bottom-hugging beauties unlike those
for raising goldfish. In truth, the halibut's journey from egg to
plate is as complicated as its twisted visage is bizarre. A tremendous
research investment is required to achieve success in the feeding,
breeding and rearing of each tasty filet. UMaine's halibut program
represents more than seven years of research into the unusual lives of
the flatfish and benefits to Maine's aquaculture industry that have
only begun to be realized.
"There has been a lot to discover with halibut,"
says Nick Brown, CCAR operations manager. "Marine species are
notoriously difficult to raise in terms of nutrition and other
factors, and since halibut spawn in deep water, we know even less
about them."
Brown and his UMaine research colleagues have
applied their considerable expertise to unraveling the secrets of
halibut growth and development, pairing their discoveries with an
adaptive, innovative approach to developing successful systems for
large-scale production. Utilizing the facility's resident adult
population, wild caught in Maine waters in 2000–01, the scientists
began harvesting eggs and milt from the huge fish and identifying
optimal conditions for hatching and rearing halibut larvae.
Every three days during breeding season, a single adult female
can supply several liters of the fragile eggs, which are carefully
blended with milt collected from the males. In a darkened room humming
with the sound of pumps and filters, long columnar tanks act as
swirling incubators for the fertilized eggs. Once hatched, the tiny,
translucent fry are at the most delicate stage in their development.
For nearly 10 weeks, they swim in much the same
way as other fish. After absorbing their yolk sac, they seek out
minuscule prey to build energy for their surprising metamorphosis.
With the proper food and environmental conditions, the bodies of the
tiny fish transform from a typical salmon-like design to the
horizontally flattened form of the adult. Their bodies twist and
flatten, their eyes migrate to one side and they slowly descend
through the water column to their new home on the ocean floor.
The slightest environmental disturbance or
nutritional deficiency can throw the halibut larvae's delicate systems
off balance, causing an irregular or incomplete metamorphosis that
leads to deformities. Brown and his team have successfully identified
the environmental and nutritional requirements for larval growth, and
can now rear tens of thousands of larvae in the Franklin facility for
research and commercial aquaculture.
Brown also has teamed up with UMaine aquaculture
nutrition expert Linda Kling. Their research, funded by a grant from
the USDA Northeastern Regional Aquaculture Center, includes the
longest-running halibut brood stock nutrition study ever conducted.
Testing two specially formulated diets against a control diet of raw
herring and squid, Brown and Kling have made significant strides
toward understanding the complex nutritional needs of adult halibut,
comparing differences in growth rates, egg production rates and larval
success based on feeding regimes.
Addressing the challenges of halibut aquaculture
in a comprehensive way has allowed the center to become a true partner
in the development of the state's aquaculture industry. By examining
everything from breeding to feeding, UMaine has been able to offer its
industry partners a head start in the growing halibut aquaculture
market.
"We have been working with UMaine since 2002 in a
business incubator-type relationship, and we are very enthusiastic
about what the future holds," says Alan Spear, president of Maine
Halibut Farms LLC of Orono. "Raising halibut commercially is a process
that requires a long lead time and considerable capital investment.
Our relationship with UMaine has given us the chance to prove our
model works and carve a niche for ourselves in the industry."
The successful relationship between CCAR and its
industry partners was highlighted by the sale of a bumper crop of more
than 25,000 healthy juvenile halibut to Maine Halibut Farms in 2006.
The fish represent the first large-scale population of commercially
grown halibut in the country and are an important step toward
establishing a halibut aquaculture industry in Maine.
Research into nutrition and rearing methods has been critical
to the program's success, but UMaine's role in developing the
fledgling halibut aquaculture industry isn't limited to researching
the fish's unique biology. CCAR's innovative facilities and management
methods are helping ensure that raising halibut will be a commercially
viable enterprise in the state. From temperature-controlled incubation
rooms to advanced recirculation technologies, CCAR's facilities and
techniques have revealed new ways to reduce costs, increase growth and
prevent disease.
One of CCAR's most important advances has been in
the recirculation systems being used to house the adult brood stock,
and in incubation and larval rearing. To maintain healthy conditions
for growth and breeding, the huge tanks require a complete water
change every hour, amounting to almost a million gallons per day
cycling through the brood stock facility.
Seawater inputs this large not only increase
energy and maintenance costs for pumps and associated equipment, but
also make temperature, salinity and other water conditions nearly
impossible to control. CCAR's recirculation system not only cleans the
water and allows technicians greater control, it also limits fresh
seawater inputs to just 4,000 gallons per day.
"With this system, we are able to filter the water
and sterilize it using ultraviolet light, as well as control salinity
and temperature in the tanks," says Brown. "We are always trying new
things to boost the efficiency of the system and reduce costs."
The filter takes advantage of the natural ability
of bacteria to break down fish wastes such as ammonia into harmless
nitrates. As pumps churn billions of bubbles through a mixture of tank
water and dime-size plastic nuggets, bacteria growing on the surface
of the plastic work their magic, creating a giant biofilter for
processing the considerable waste produced by dozens of adult halibut.
With 25,000 young halibut at CCAR, a major
facility expansion is under way. Giant concrete tanks and new
technologies have been installed to expand the program's ability to
grow halibut to a market size of 5–10 pounds, and market tests are
being conducted to determine if smaller, plate-sized halibut would
appeal to consumers. Capable of supporting 500,000 fish, the new
expansion will allow CCAR and its industry partners to complete the
progression from proof-of-concept experimentation to demonstrable,
large-scale production.
The successful expansion is clearly a good sign
for Maine's aquaculture industry.
"Restrictions on wild-caught halibut have opened
up more markets in Boston and New York for farmed halibut, and most of
what's being raised currently is coming from Norway, Scotland and
Canada," says Spear.
"This new phase of the project will bring us up to
a production level of 20 tons per year," he says. "When we take the
next step to 200 tons per year, we'll have a real, viable business
under way."
by David Munson
January-February, 2008
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