14 



Results . --Pertinent re-:.ults from the two populations are 

 compared in Table 5. It was both a surprise and a disc.ppointment 

 that the pond fish, which presumably had all they desired to eat 

 at all times, attained a total weight of only 226.6 pounds (102.28 

 kilograms). The 234.5 pounds (106.36 kilograms) of food which 

 passed through the demand feeder (conversion 1.21) was supplemented 

 by the normal pond organisms, plus an unknown number of the co- 

 existing fry. Since only approximately 700 Age catfish were re- 

 covered out of an original stocking of a large spawn, predation of 

 these small fish could have been substantial; howevf^r, a conver- 

 sion rate of 1.21 indicates that no large amount of the pelleted 

 food was wasted. It would seem to be significant that as many 

 pounds of fish v;ere produced in 262.5 cubic feet (7.43 cubic meters) 

 of raceway volume as in the 1-acre (0 .4-hectare) pond, and in a 

 lesser number of days. On the basis of results reported by Allen 

 (1972), production in the rs^ceway might well have been larger with 

 a more efficient balance between stocking density and rate of flow. 

 In a series of experiments in 420-gallon (11.89 cubic meter) tanks, 

 Allen (op. cit. ) attained standing crops as high as 5,7 pounds per 

 cubic foot (bl.3 kilcgrens per cubic meter), finding that the most 

 efficient use of his facilities was obtained at a stocking density 

 of 10 fish per cubic foot (353 fish per cubic meter), and a flow 

 rate of 4.5 gallons (17.03 liters) per minute. Flow rates of 

 12.5 GPM (47.32 liters per minute) were found to have an adverse 

 effect on net production when combined with densities of 5 and 10 

 fish per cubic foot (177 and 353 fish per cubic meter). Our flow 

 rate of 80 GPM (303 liters per minute) may h:ive reduced production 

 substantially below what might have been obtained at a more optimum 

 flow rate. 



On the basis of known amounts cf the pelleted food presented 

 to the fish, conversion rates were 1.21 in the pond, and 1.06 in the 

 raceway. A rate as lov; c.s 1.21 in th'. pond was not unexpected be- 

 cause of the availrbility of a suppleiaentary diet of catfish fry, 

 crayfish, and other natural foods. The lower rate of 1.06 in the 

 raceway indicates thct the Gmcyiit of natural food which entered the 

 catch basin in the continuous flcv/ of lake water must have been 

 large. The source of this v/ater w?.s £. 10- inch (25.4-centimeter) in- 

 take pipe located in the reservoir at a depth which varied between 

 3 and 5 feet (1 and 1.5 meters) over the period of study. Many 

 forms of aquatic life, inclu'"ling s.rall fish, crayfish, a large 

 variety of insect larvae, and occasional heavy loads of zooplankton 

 were knovm to pass through this supply system. When pelleted rations 

 are supplemented by the quantity of natural food that is believed 

 to have entered the catch :-v-Lsin raceway, it would probably be pos- 

 sible to use a less co-.rylctn and less expensive food than required 

 when the v/ater is filtered, or originates from a well. 



