Stephanie Grodeska | 11/2/2016 6:33:31 PM
Cocahoe Production Systems
There are two types of production scenarios regardless of the growing facility (whether ponds, pools or recirculating systems). These scenarios are the two-phase system, which uses two isolated units: one for broodstock to produce eggs and the other to hatch and grow the minnows to market size. The three-phase systems have separate units for broodstock, hatching eggs, and grow out (Figure 1). A dependable supply of salt or brackish water of good quality and quantity is very important to the successful culture of killifish in a production facility. Size of production system is usually dependent on the water to refill between crops and the quantity of fish that can be handled safely. The systems used in production are summarized below.
Pond aquaculture is one of the oldest methods of growing
fishes. Pond culture has been used successfully in raising
cocahoe minnow in several southern coastal states. Growth
of cocahoes is inversely related to stocking density; hence
juvenile minnows (0.3 g to 0.5 g each) have been grown at
50,000 to 200,000 fish per acre in grow-out ponds depending
on how soon they are needed on the market. Generally, the
lower the stocking density, the faster the growth will be.
The optimum pond size has not been evaluated because
most of the experimental studies have used smaller ponds (about 0.2 to 1 acre surface area). Natural productivity
is critical to the successful culture of cocahoe minnows in ponds hence water should be fertilized to stimulate
production of natural foods. Pond bottoms should be smooth and well graded to allow easy drainage. Culture
ponds should have catch basins to assist in harvesting fish
(Figure 2). Ponds of approximately 3-4 feet average depth
having about 1.5 feet at the shallow and 5 feet at drainage
end are good for minnow culture. All ponds should be filled
with water that is passed through a fine cloth filter, about 800
microns or 0.03 inch is recommended, to eliminate wild fish
that could compete for
food or eat the cocahoes.
Above ground tanks made of plastic or fiberglass have been used as pools
for growing minnows. Research at the Aquaculture Research Station has
utilized pools with bottoms filled with dirt, which has proved to be valuable
in regulating ammonia concentrations. As in ponds, natural productivity in
pools is very important as it provides supplemental nutrients, which may be
absent or in insufficient amounts in the artificial diets given to the minnows.
Cocahoe Production Systems
Figure 1. Two and three phase system.
Figure 2. Lateral diagram of ideal pond form.
Figure 3. Fiberglass pools used for egg
production. Photo: Craig Gothreaux
Using pools instead of ponds has several advantages. Predation can be controlled from birds and other mammals
as pools can be covered with nets. In addition, there are no problems with seepage from the surrounding area,
which can contaminate pond water and even become toxic to fishes.
Recirculating Aquaculture Systems (RAS)
Compared to ponds and pools, this is a rather recent technology for growing fish. Unlike the ponds and pools, this
system enables the growing of fish at high densities in indoor tanks with a “controlled” environment for year-round
production. In using RAS, farmers need very good biofilters to regulate nitrogenous wastes like ammonia. Many
RAS units contain ultraviolet (UV) filters and other sterilization tools to keep algae and pathogens (associated with
diseases) out of culture tanks. However, they are not required in all cases. Tanks need to be aerated continuously
to supply DO to the minnows.
RAS offer fish producers a variety of advantages over pond culture. These include a method to maximize production
on a limited supply of water and land, nearly complete control over the culture environment to maximize growth,
the flexibility to locate production facilities near markets, complete and convenient harvesting, and quick and
effective disease control.