Satiation Feed Consumption as an Inventory Tool to Assess Biomass of Channel x Blue Hybrid Catfish in Earthen Ponds

Abstract

The present study was conducted to determine the percentage body weight of feed that specific sizes of hybrid catfish consume at various water temperatures when fed to satiation under pond conditions. This information, along with the quantity of feed provided per pond, was used to estimate the fish biomass in any given pond. It was hoped that this technique would provide an economical alternative to farmers in search of better inventory assessment tools. Hybrid catfish were stocked into 0.04 ha ponds at a density of 4,000 fish/ha, by size categories of fingerlings, stockers, food-size, and large food-size fish. Large food-size fish were stocked at a lower density of approximately 1,750 fish/ha. The fish were fed to satiation at water temperatures of about 15, 20, 25, and 30 C. Satiation estimates were obtained for each pond a minimum of three times prior the last satiation feeding. The total weight of feed consumed was calculated in two different ways. First it was determined by assuming that all of the feed was consumed. The second way used a correction factor that assumed fish only ate the feed that floated and ignored any that sank to the bottom of the pond. Forty-five minutes after the last satiation feeding the ponds were seined and a sample of 25 individuals per pond was harvested. Each fish was weighed, the stomach dissected, and the number of pellets found in the stomach counted. The number of pellets per unit weight of dry pellet feed was determined in advance, and based on the pellet count, a weight of dry pellet feed consumed was calculated and expressed as a percent body weight of feed consumed. After the last satiation feeding, any pond that was sampled was harvested and the biomass was determined after holding the fish approximately 24 hours. Fish biomass was estimated based on the average percentage of body weight consumed from the sample of 25 fish for each pond and was converted to a standing crop as kg/ha. The standing crop estimate was then compared to the actual standing crop from the day of harvest to verify the accuracy of the technique. Results of the study suggest that both fish size and temperature had a significant effect on the percentage of body weight consumed. Overall, after applying correction factors, the technique was only effective in estimating 30.8% of the cases within 10% of the actual standing crop. However, when fish were feeding actively and consistently (such as the stockers at 25 and 30 C) the estimated standing crops were within 10% of the actual standing crops on 75% of occasions. Nevertheless, in most circumstances the use of satiation feed consumption is not an effective tool for estimating fish biomass.