Fishfarming pen
A fish cage for use in water comprising a main part ( 1 ) made of a watertight, substantially rigid material and has an outlet for effluent ( 12 ). The main part ( 1 ) is substantially hemispherical, and may slip unhindered through the water along a spherical path without influencing the body of water inside the cage substantially. Because the forces acting on the main part ( 1 ) from the surrounding water act mainly along the shell as opposed to perpendicular to the shell, the risk for tearing and the risk for swashing are reduced. Embodiments having flow and lighting conditions adaptable to different species are also disclosed. The cage can be localized in areas with currents and waves, and it can easily be adapted for different species.
1. A fish cage for use in water, the fish cage comprising:
a main part comprising a watertight, substantially rigid hemispherical shell having an outlet for effluent, wherein a rigidity of the shell is substantially constant, wherein the shell includes a substantially circular opening that defines a plane, and wherein the shell rotates in the water about an axis lying in the plane; and
at least one nozzle that provides a rotational flow of water around central axis extending perpendicularly through the plane, wherein the flow has approximately equal tangential velocity from the circumference of the main part to a region near the central axis.
2. The fish cage according to claim 1 , wherein the main part is suspended from a floating collar.
3. The fish cage according to claim 1 , wherein the main part is a sandwich structure comprising a substantially gas filled layer between an inner shell and an outer shell.
4. The fish cage according to claim 1 , wherein at least one substantially horizontal shelf extends from a circumference of the substantially circular opening inwards toward a central axis extending perpendicularly through the plane.
5. The fish cage according to claim 1 , wherein the main part further comprises a watertight cover for submersing the fish cage in water.
6. The fish cage according to claim 1 , further comprising at least one supportive element that extends from a circumference of the substantially circular opening inwards toward a central axis extending perpendicularly through the plane.
7. The fish cage according to claim 1 , wherein the at least one nozzle is configured to change orientation to reverse the flow from one rotational direction to an opposite rotational direction.
8. The fish cage according to claim 1 , wherein the main part is covered by an opaque cover, and at least one light source is disposed within the main part.
9. The fish cage according to claim 1 , wherein the at least one nozzle is disposed on an elongated body extending from a circumference of the substantially circular opening toward the central axis.
10. The fish cage according to claim 9 , wherein the elongated body comprises an inner pipe disposed in and, in slidable, concentric, and liquid-tight engagement with an outer pipe, the outer pipe comprising at least one first opening for outflow of water in a first direction, and at least one second opening for outflow of water in a second direction, the inner pipe comprising at least one opening that can be aligned with either the first opening or the second opening, whereby a relative movement of the inner pipe within the outer pipe causes the water to flow out from the elongated body in the first or the second direction.
11. The fish cage according to claim 7 , wherein the at least one nozzle is disposed on an elongated body extending from a circumference of the substantially circular opening toward the central axis.