HPL
Oyster Hatchery
| overview | personnel | cooperative
programs | links |
The
oyster hatchery at Horn Point is part of a major cooperative research
and education effort by the University of Maryland Center for Environmental
Science and the Sea Grant Extension Program.
The
program revolves around the original 5,500 ft2 Aquaculture
Research Laboratory and the network of agents and specialists that
work with the Sea Grant Extension Program. This program, designed
to bring together shellfish specialists, hatchery biologists, and
educators with oyster growers, students, and other concerned citizens
has been in operation since the mid 1970s. A variety of changes
in the size and scope of the program as well as changes and improvements
in facilities have occurred over time.
Recently,
emphasis on the plight of the oyster resources in Chesapeake
Bay and elsewhere have brought about an increase in interest
in oyster hatcheries as they are beginning to be viewed as
viable resources in the fight to bring about major oyster restoration
projects in the Upper Chesapeake Bay. Working with outside
groups and agencies, the hatchery at Horn Point has seen its production
of eyed larvae and spat on shell increase each year beginning
with 1994. Currently
this facility produces in excess of one to two billion eyed-larvae
and over 50 million spat on shell for use in its program.
The
Shellfish section of this facility is comprised of three major
components, each dealing with a major area of emphasis for
oyster production. The production of cultured algae for use
in feeding larval oysters and newly settled spat is accomplished
through the use of a series of culture steps, ending with large
open vats capable of producing several thousand liters of cultured
algae each day.
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Algal
Carboys |
Greenhouse
addition to Hatchery |
Mass
algae culture tanks
in greenhouse |
Broodstock
are conditioned in a flow-thru system using water pumped from the
Choptank River. River water used in conditioning is tempered using
a system of plate heat exchangers and then mixed with unfiltered
ambient river water and distributed to the broodstock conditioning
system where it is allowed to pass over the conditioning oysters.
In this way oysters are fed using the natural algal cells found
in the Choptank River water without supplemental algal feeds. If
needed, cultured algae can be introduced into this system to provide
additional nutrition to broodstock if natural populations of phytoplankton
are too low. Oysters placed in this system will go from "winter" condition,
where they contain no visible gonadal systems to "spawning" condition
in six to eight weeks.
Once
broodstock ripen and are in full spawning condition, they are
removed from the conditioning system and placed on the spawning
table. Using a combination of warm water and gonadal products,
spawning is induced. In general, ripe broodstock will spawn in
two hours or less in this system. Problems with low salinity,
disease, or other water quality associated problems may delay
or inhibit this activity.
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Spawning
Table with pans to collect male and female gametes. |
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Eggs
are counted and sperm is added to insure fertilization and the
newly fertilized embryos are distributed into large larval tanks
filled with filtered Choptank River water at 26oC
to 30oC. where
they are allowed to develop and grow. Fed daily with cultured algae
normal larval periods range from 11 to 20 days depending upon conditions.In
general the majority of the larvae produced from this facility
are produced using a "mass spawning" technique where
a large number of broodstock are placed into a compartment on the
spawning table and allowed to spawn together. Once spawning begins
males and females which spawn very differently are separated by
sex and allowed to spawn to completion in plastic tubs. During
this period larval oysters go through several changes from embryo
to trochophore to straight hinge, to umbo, to pediveliger (or eyed)
stages. Once pediveliger or eyes stage has been reached the oysters
are ready to stop swimming and settle to the bottom to look for
an appropriate substrate for them to attach to. This process is
called settlement or setting and in reality is a metamorphosis
for the oyster and is very stressful. Mortalities are often severe
during settlement sometimes exceeding 90%.
At
the Horn Point hatchery most eyed larvae are used to produce spat
on shell for use in various outplanting experiments or demonstrations.
This simple process begins with the production of large amounts
of substrate for the oysters to set upon. In the Horn Point hatchery,
like most other production setting systems that produce spat on
shell, clean aged oyster shell is loaded into plastic mesh bagging
material for ease of handling. These bags are then placed in large
setting tanks which are then filled with warm river water. Eyed
oyster larvae are added along with algal food and the tank is aerated
to provide adequate distribution of the larvae throughout the tank.
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Piles
of shellbags ready for use in setting tanks. |
Students
loading shellbags into setting tanks. |
Within
48 hours the larvae should have completed metamorphosis and settled
onto the shells in the tanks. At this point ambient river water
is introduced into the tank to provide food for the newly settled
oysters. Oysters are now known as spat and quickly grow on the
shells. Three to seven days later they have grown enough to be
handled and are ready to be transported to the nursery where further
growth and hardening will take place.
In
the Chesapeake Bay the nursery process takes four to eight weeks.
During this time the spat will go from an almost invisible size
of under 1 mm to over 15 mm. At this point they are ready to
withstand the rigors of movement and are large enough to survive
being planted on the bottom for growout.
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Survival
in the nursery phase of the operation has been excellent at
Horn Point sites approximating 70%. To date over 100 acres
of oyster beds have been planted using oysters produced from
the Horn Point hatchery. Growth and survival of these spat
has exceeded expectations and many have reached market size.
Plans are to greatly expand efforts using hatcheries as tools
for oyster rehabilitation in Maryland.
The
addition of a 2,400 ft2 greenhouse
to the hatchery in 1998 has greatly expanded the capacity of the
Horn Point facility. This new greenhouse along with a greatly improved
setting and cultch handling system is capable of producing over
4 million spat on shell per week during the peak setting season.
With this expanded facility came the need for greater manpower,
more funding and a host of other logistical problems. These have
been solved by establishing a cooperative
program that
incorporates support from a host of other groups and individuals. |
| Spat
on shell produced at HPL. |
Personnel:Dr.
Donald W. Meritt (Program Director) meritt@hpl.umces.edu
Stephanie
Tobash (Hatchery Manager) tobash@hpl.umces.edu
Angela
Padeletti (Hatchery
Technician)
apadelet@hpl.umces.edu
Melissa
Radcliffe (Algologist) mwood@hpl.umces.edu
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