13 



Our original test in 1969 was conducted with the thought 

 that the technique might present a practical and relatively 

 economical method for improving the quality of fishing in public 

 waters, and subsequent developments in Iowa suggest that this may 

 be true, Conley (1972) has reported on a program wherein the 

 Iowa Conservation Commission provides fingerling channel catfish 

 to County Conservation Boards for rearing in cages and eventual 

 release into the County-owned lake in which they were reared. 

 The program was initiated in 1971 in 25 lakes having a total 

 acreage of 2,500 acres, (1,012 hectares) and preliminary evalua- 

 tions encouraged expansion of the program. Success in terms of 

 returns to anglers is not yet fully known, and will be a matter 

 of great interest. 



CHANNEL CATFISH PRODUCTION IN A MODIFIED RACEI^TAY 



Materials and Methods . — All of our 1-acre (0.4-hectare) 

 ponds drain into a cement "catch basin" that has an effective hold- 

 ing area 12 feet (3.66 meters) long and 7 feet (2.13 meters) wide. 

 Between draining operations the basin can be used as a holding tank, 

 or as a modified raceway. On June 2, 1972, the basin was stocked 

 with 32.8 pounds (14.9 kilograms) of 4-inch (10-centimeter) catfish 

 (about 1,575 in number). The basin was maintained at a depth of 

 38.5 inches (0.98 meter) with water gravity fed directly into the 

 basin from a 585-acre (236. 7-hectare) reservoir at a rate of 

 approximately 80 gallons (303 liters) per minute. This rate of 

 flow provided a complete exchange of water in the basin approximately 

 once every 25 minutes. The water entered the basin below water 

 level and a 1/4-inch (6.4-millimeter) screen was placed over the 

 outlet pipe to prevent the fish from entering the line. The initial 

 stocking rate was at a density of about 6 fish per cubic foot 

 (212 per cubic meter). On July 12, 1972, 150 fish weighing 11.6 

 pounds (5.28 kilograms) were removed, leaving a density of about 

 5 fish per cubic foot (177 fish per cubic meter). Twice daily, for 

 5 days each week, the fish were fed all of the Purina trout chow 

 that they would consume in 5 minutes. At the time of harvest this 

 daily ration was found to be 1.9 percent of the weight of the fish. 

 Final census occurred on September 28 after a growing period of 

 118 days. Over a slightly longer period (132 days), a similar 

 number (1,250) of fish of the same initial size were maintained in 

 a 1-acre (0.4-hectare) pond and fed a sinking ration from a demand 

 feeder. This pond was also stocked on June 29 with a large "spawn" 

 of channel catfish fry which were fed a starter meal. 



