Accurate length, weight or size information may also be required for research purposes. Food fish growers may want to grade fish to avoid harvesting fish too small for marketing or processing. Processors may want to have fish graded because of differences in the value or demand of fish by size. Grading requires additional labor, time and equipment but in many markets it is essential and may improve profits. A variety of commercial graders is available.
Many producers construct grading devices specially designed for use in their facilities.
Based on the market situation, know the size or sizes of fish that require sorting before purchasing or constructing a grader. Grader panels or grills can be purchased and inserted into homemade frames to save money. PVC pipe is a popular material used in making graders. Plastic netting is also available in various meshes and can be used for grading small fish when the material is strong and well supported. Fish are injured less if the grading material is smooth and non-abrasive, without any sharp edges or roughness.