Animal husbandry – Aquatic animal culturing – Fish culturing
Reexamination Certificate
1999-08-26
2001-07-31
Jordan, Charles T. (Department: 3644)
Animal husbandry
Aquatic animal culturing
Fish culturing
C043S100000, C043S101000
Reexamination Certificate
active
06267079
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of fish containment devices and, more particularly, to an improved open water fish cage.
BACKGROUND OF THE INVENTION
Aquatic net cages or pens of various shapes and sizes have been used for many years to contain fish for the purposes of research, breeding and raising fish for food. Cages designed for the breeding and/or raising of fish for consumption either float or rest at the bottom of an outdoor body of water. Generally, such cages have an access opening in the top of the cage and are often designed to retain man-made fish food within the cage by providing an overlay of netting on the cage bottom with a mesh size that is substantially smaller than the other netting that covers the cage. Such cages may also include fish grading screens of either netting or parallel bars to separate the smaller fish prior to harvesting the larger fish.
Aquatic net cages for research purposes are also known. For example, some cages are designed to study the effect of pollutants on fish growth. However, such cages are often designed to isolate the different species being studied from each other and/or predators. Thus, such cages have a very specialized research purpose and a relatively complicated construction. In other studies, round cages suspended in a body of water may be used to study the predatory behavior of fish populations.
It is also known to use cages that rest at the bottom of a body of water to study in situ fish growth. Fish growth is affected by environmental conditions, such as the availability of food, dissolved oxygen concentrations, water temperature, pollutants, etc. Therefore, in contrast to cages in which fish are raised for consumption, in fish growth studies, preferably, all of the food should come from the local environment; and no man-made food should be provided. Cages to study fish growth are often bottomless, so that the plant and animal life is readily available as food for fish being studied. However, a bottomless cage has several disadvantages. First, access to the cage is through a relatively small opening or door generally in the top of the cage, and thus, removal of fish from the cage must be done with a dip net or suction gun. In turbid water in which the visibility is limited, the removal of fish from a bottomless cage with a dip net or other device is very difficult and time consuming. In very turbid water with close to zero visibility, such a task is almost impossible. Further, deploying and retrieving fish in a bottomless fish cage in turbid water from a boat is also very difficult if not impossible. Therefore, fish growth studies using bottomless cages must be limited to less turbid or shallower waters. Further, in view of the difficulties in handling fish in a bottomless cage, such cages are often made smaller, thereby severely limiting available food supply and thus, the number of fish that can be studied in each cage.
Therefore, there is a need to provide an improved fish cage for in situ fish growth studies that does not have the disadvantages of known cages.
SUMMARY OF THE INVENTION
The present invention provides an improved fish cage that permits fish to be easily handled during in situ fish growth studies that are performed in deeper waters and in turbid waters, even waters having zero visibility. Further, the above is achieved by a fish cage design that protects the fish being studied from predators and competitors for food while permitting both ambient water with suspended particles to circulate through the cage and plant and animal life on the bottom of the water to enter the cage. Thus, the fish in the cage of the present invention can live for extended periods of time in their natural feeding environment. The fish cage of the present invention has the further advantage of permitting the cage to be easily removed from the water with complete retrieval of the fish being studied. Another advantage is that the cage may be made relatively large so that larger fish populations can be studied, and in addition, advantageously, the fish cage of the present invention is economical, simple to manufacture and has a durable long life.
In accordance with the principles of the present invention and in accordance with the described embodiments, the present invention provides a fish cage having a frame defining an enclosure having a top, a bottom and an intersecting side wall. The frame is adapted to rest at the bottom of an outdoor body of water and is covered with a first netting on the top and side wall but not the bottom. The first netting has mesh openings sized to permit ambient water and suspended particles therein to circulate through the cage but prevent predators and competitors for food of the fish under study from entering the cage. A second netting covers the bottom of the enclosure, and the second netting has second mesh openings larger than the first mesh openings. The second mesh openings of the second netting are sized to first, prevent the fish being studied from leaving the cage and second, to permit the natural environment of plant and animal life at the bottom of the body of water to enter the enclosure, thereby providing a more natural environment for the fish under study. The enclosure includes a door permitting access to the interior of the enclosure.
In one aspect of the invention, the frame is multilateral, for example, rectangular, and made from perforated plastic tubing. In another aspect of the invention, the door is a flap of netting cut from the wall or the top of the enclosure. In a still further aspect of the invention, a second door of a netting material covers the first door.
These and other objects and advantages of the present invention will become more readily apparent during the following detailed description together with the drawing herein.
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Eby C. Richard
Jordan Charles T.
Nelson Judith A.
Wood Herron & Evans L.L.P.
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