MAJOR BREAKTHROUGH IN HATCHERY AND OFFSHORE AQUACULTURE TECHNOLOGY IN THE SE US AND THE CARIBBEAN
New methods of spawning and raising fish are bringing
the prospect of an environmentally sustainable and commercially viable
marine fish aquaculture industry one step closer to becoming a reality.
During the last 4 years, the Aquaculture Center of the Florida Keys, Inc.
(ACFK) joined efforts with the Aquaculture Program of the University of
Miami's Rosenstiel School of Marine and Atmospheric Science (RSMAS) to
refine hatchery technology of high value species of marine fish. The
research and development effort, partially funded by the government through
the National Oceanic and Atmospheric Administration, has focused on
scientific aspects leading to improved hatchery technology of mutton
snapper, Lutjanus analis, and cobia, Rachycentron canadum.
This summer, tens of thousands of cobia and mutton snapper fingerlings have
been successfully reared at the ACFK hatchery in Marathon, Florida Keys.
"This is the first time that captive mutton snapper and cobia have
spawned naturally on the sole basis of manipulating environmental cues, such
as varying the water temperatures between 20? and 28?C," says Daniel
Benetti, associate professor and director of the Aquaculture Program at
RSMAS who is the principal investigator of the project. The fingerlings were
shipped and stocked into two offshore cages, submerged in deep waters off
the coast of Culebra Island, Puerto Rico. Snapperfarm, Inc. is developing
the offshore aquaculture demonstration project tin Puerto Rico with
technological support from the UM (RSMAS) Aquaculture Program and assistance
of PRIDCO (Puerto Rico Industrial and Development Corporation). The
University of Puerto Rico is collaborating with the University of Miami for
conducting environmental assessment and social and economic studies related
to the development of the operation.
"Both the hatchery production of high-value marine fish and the
growout, stage are major breakthroughs", says Benetti. " The main
bottleneck for the development of a marine food fish industry in the U.S. is
the consistent spawning of broodstock fish and raising of larvae and
fingerlings at the hatchery", says Owen Stevens, ACFK hatchery manager.
"And this has been accomplished by the ACFK/UM project", adds
Jorge Alarcón, who is in charge of the hatchery's breeding program. As for
the growout demonstration project, "unlike some traditional aquaculture
practices that can have negative impacts on marine environments, the
offshore cage systems are among the most environmentally sustainable methods
for commercial marine aquaculture because they are placed at greater depths
and are farther from shore", says Snapperfarm's president Brian
O'Hanlon.
The offshore cage system is completely submerged to preserve the aesthetic
aspects of the area. The depth of the site (minimum 100 ft) and steady
current (ideally between 0.5-1.5 knots) maintain water movement in a
downstream direction, dispersing organic and inorganic waste that might be
associated with aquaculture operations. No coral reefs are present in
the area surrounding the cage systems. Rather, sparse patches of
Halimeda - a macroalgae characteristic of nutrient-poor environments - are
found at the sandy bottom. The cages, stocked with hatchery-reared
fish for growout, inevitably generate a certain amount of nutrients and
suspended solids. To offset this, scientists plan to place, downstream
from the cage site, rafts and longlines of filter feeder mollusks and banks
of macroalgae to absorb the nutrients being released by the system.
"One of the most unique characteristics of the offshore aquaculture
system is that it can be entirely self-sufficient", says Snapperfarm's
principal Joe Ayvazian. For now, fish are still being hand-fed by
divers and water samples are being manually collected for analysis. In the
near future, automated feed hops loaded with environmentally friendly feeds
will automatically dispense pre-calculated rations to ensure the highest
assimilation and growth rates by the fish with minimal organic and inorganic
wastes (feeds, feces and nutrients).
"A key determinant in the success of major aquaculture operations is
the ability to monitor the biomass and water quality parameters such as
temperature, salinity, oxygen, pH, suspended solids, as well as nutrients,
in order to determine whether feeds are being dispensed at the optimum
rate," says Benetti. "We will be able to this by installing
independent monitoring devices with several sensors in the cage system.
A monitoring device will gather and transmit real time data via satellite to
computerized systems in the control room of the lab".
Not only does the offshore aquaculture concept provide a sustainable
alternative, but properly developed, it may lead to raising organisms that
feed low in the food chain such as mollusks and algae, which can only be
cultured in nutrient rich areas.
"Nutrients and solids being released by the fish cages create a
favorable environment for raising species of mollusks and algae that, while
removing the organic and inorganic nutrients from the area, could, in turn,
provide additional crops," says Benetti.
Cobia are exhibiting extraordinary growth rates in the offshore cages:
fingerlings grew from 2-12 grams and 5-10 cm to about 400 grams and 25-30 cm
in 45 days, with survival rates of nearly 100%. It is estimated that the
fish will grow to 6-8 kg (12-15 lb) in one year.
For more information on the hatchery and offshore aquaculture system go to:
http://www.snapperfarm.com/rsmas
(From Aquaculture Info List, e-mail: dave.conley@sympatico.ca)