| 摘要 |
The device 1 is formed from an array of generally rectangular apertures 2, each of which is formed by two long tubes 3 and two short tubes 4 of plastics material mounted to a loop of fishing net 5. Each loop of fishing net 5 is formed by crimping the ends of the loop by means of a metal crimp 6. Each of the tubes 3, 4 can rotate freely about its longitudinal axis, so that a fish brushing against a tube 3, 4 will cause the tube to rotate, and will therefore avoid becoming snagged on the tube. When such a fish grading device 1 is included in a fishing net and the net is dragged through the water, small fish are able to swim through the rectangular apertures 2, whereas larger fish are not. Thus only fish of a desired minimum size are caught. |
