Adjustable large yellow croakers grading device

An adjustable large yellow croakers grading device comprises a net cage, a fish pump and a grading box, wherein the net cage is connected with the fish pump; the fish pump is connected with the grading box; the grading box adopts a groove-shaped structure formed by frames; the frames include an upper frame and lower frames; a mesh sheet is arranged between the lower frames; mesh sheets and a grading fence are arranged among the upper frame and the lower frames; the grading fence includes a plurality of fence bars with irregular polygonal sections; a transmission device arranged on the upper frame drives the grading fence to rotate, and comprises gears and a chain; a bearing driving the grading fence to rotate is arranged on the lower frame, and is connected with a motor; centre cylinders are arranged in the fence bars; the top of each centre cylinder is connected with a gear; the bottom of the centre cylinder is connected with the bearing to drive the fence bar to rotate; and each gear is connected with a dial scale used for adjusting and controlling the space between the fence bars. The adjustable grading device can be used for performing multi-level adjust and control grading on large yellow croakers according to the requirement of a farm, so as to save labor force, and reduce error caused by manual visual estimation and death rate of the large yellow croakers caused by weighting the large yellow croakers with a steelyard.