Research Highlights - AFC Urban Fishing Program

Aquaculture/Fisheries Center Research Highlights

In-Pond Fish Grader

Evaluation of a new in-pond mechanical floating grader for food-sized channel catfish, Ictalurus punctatus
Jeremy Trimpey, David Heikes, and Carole Engle

Grading is a common practice in the culture of many fish species that involves separating a population of various sized fish into groups of similar size classes. There are a variety of techniques used to grade fish that have evolved through time with changes in technology and demand. Mechanical, box, vertical drag, and sock (net) grading have been adapted for use in grading channel catfish. While mechanical grading has been attempted for commercial catfish, the industry standard continues to be passive grading in socks (nets). However, it has been reported that the catfish industry loses over $100 million annually due to inefficient harvesting, grading, and transport. A new mechanical grader has been developed at the University of Arkansas at Pine Bluff to replace traditional methods of grading food-sized channel catfish.

Grading trials are underway to compare the performance and efficiency of the UAPB/Heikes grader with the traditional live car method (nets) at the UAPB Aquaculture Research Station and on commercial catfish ponds. The performance is measured as the kg of fish graded per minute. Efficiency between the two graders is accomplished by comparing overgrading (percent of sub-harvestable fish graded through with harvestable fish) and undergrading (percent of harvestable fish not graded). This will be accomplished by taking equivalent weights from a seine haul and grading those with each grading method. These trials will be held in three different ranges of water temperatures: cold (< 10° C), intermediate (14° to 26° C), and hot (> 27° C). During the UAPB trials three different size ratios (harvestable to sub-harvestable) of fish were stocked out in ponds: 75%/25%, 50%/50%, and 25%/75%. There will be three replicates of each trial at each temperature range with each ratio of fish sizes. The commercial trials will be replicated three times for each temperature range with the ratio of fish sizes that results from their farming practice. Figures 1 and 2 illustrate results from two trials held during the hot temperature range at UAPB.