Abstract: A fish rearing system having a water circulation system comprising: a trapping section including a particle trap 2 for capturing residual feed and fish feces contained in the water, a sediment trap 6 for accumulating a sediment in a rearing tank and separating the sediment from the water, a residual feed detecting sensor 5 interposed in a pipe 4 communicating with the particle trap 2 and the sediment trap 6, and a micro-screen filter 7; a denitrification device 12 for denitrifying a nitrogen compound dissolved and contained in the water; a bubble surfacing device 11 for generating bubbles by supplying air and/or ozone and removing surface active substances contained in the water by capturing the bubbles; an ultraviolet disinfection device 13 for disinfecting the circulating rearing water; an ammonium treatment section consisting of a immersion treatment device 15 and a non-immersion treatment device 14 and having a function of decomposing ammonium contained in the water; and an aeration device 21 for dissolvi

Abstract: A fish breeding apparatus is disclosed, which comprises a frame body for the fish breeding framed by connecting rod elastic reinforcements to each other into a polygon at a side number of 4 to 30 through bent couplings, and a mooring cable connected at its one end to each of the bent couplings.

Abstract: A floating frame member for use in a fish breeding apparatus, which is a hollow rod-shaped elastic body constituting a main part of a gas chamber therein, said elastic body being composed of rubber or rubbery elastic material and reinforced with fiber cords to have an outer diameter of about 279.4-about 609.6 mm (11-24 inches), a thickness of about 12.7-50.8 mm (1/2-2 inches) and a product between a Young's modulus and a sectional secondary moment of 100-3,000 kg.multidot.m.sup.2, and having a ratio of circumferential stress to axial stress of 1.5-2.5 when an internal pressure of 0.1-20 kg/cm.sup.2 is applied to said elastic body.

Abstract: An apparatus for floating and sinking fish breeding netted tanks comprising a floating and sinking mechanism composed of a flexible bag enclosed in a tubular frame and adapted to be supplied with a fluid under pressure and to remove it so as to float and sink the fish breeding netted tank.