Research Highlights - Farm Pond Management

Aquaculture/Fisheries Center Research Highlights

Pond Hatchery Management

Growth, yield and survival of tank-hatched golden shiner fry fed two practical diets
Rebecca Lochmann, Nathan Stone, Melinda Bodary and Harold Phillips

A 10-week pond study was conducted to evaluate the growth and production of tank hatched golden shiner fry fed diets containing isonitrogenous levels of either fish meal + blood meal, or poultry meal. Newly hatched fry were stocked on May 7 into 12, 0.1-acre earthen ponds at a rate of 405,000/acre. During the week prior to stocking fish, ponds were filled to ½ of maximum depth (approximately 1/3rd of total volume) with well water and fertilized with cottonseed meal at 100 lb/acre and 10-30-0 liquid fertilizer at a rate of 1 gallon/acre. A second application of liquid fertilizer at the same rate was made on May 16. Reservoir water was added slowly to the ponds until they were completely full on May 23, two weeks after stocking. Two practical diets simulating commercial minnow meals (36% protein) were made. The diets contained approximately 8% total of fish meal (FM) plus blood meal, or poultry meal (PM). Fish were fed twice daily at a rate of 5 lb/acre/day initially, and the rate was increased to 7 lb/acre/day for the second half of the study. In each pond, pH was measured every afternoon for the first week, then weekly. Temperature and dissolved oxygen were measured several times per week. Zooplankton samples were collected, identified and counted, and ammonia and Secchi depth were measured weekly. Subsamples of fish were collected weekly from each pond to track growth using an image analysis system.

At harvest (July 16-18), all fish were removed from each pond and bulk-weighed. Individual weights and lengths of fifty fish from each pond were also determined for calculation of condition. Total yield did not differ between treatments (538 ± 170 lb/acre and 522 ± 119 lb/acre for FM and PM diets, respectively). Feed conversion averaged 0.9 ± 0.2 for both treatments. Fish fed the FM diet averaged 3.1 lb/1000 (1.4 ± 0.8 g) at harvest, and were larger (P = 0.08) than the fish fed the PM diet (1.8 lb/1000 fish, or 0.8 ± 0.2 g). Survival of fish fed the PM diet (79 ± 21%) was higher (P = 0.09) than that of fish fed the FM diet (54 ± 25%). However, on the day of stocking, afternoon pH readings were 9.0 to 9.2 in six ponds and survival at the end of the study was inversely related to pH on this first day (R2 = 0.71). Of the ponds randomly assigned to the poultry meal diet, by chance, 5 of the 6 ponds had first day pH levels below 8.9, while 5 of the 6 ponds assigned to the fish meal + blood meal diet had pH levels above 9.0. Thus it is possible that afternoon pH on the day of stocking, or factors related to the pH, may have contributed to the differential survival found in the two diet treatments. Condition of fish fed the PM diet (107 ± 11) was better (P < 0.0001) than that of fish fed the FM diet (102 ± 9). One week after harvest, groups of 10 fish from each pond that had been retained in the lab and fed their experimental diets were placed into water with a pH of 10 to test their stress resistance. Mortalities were counted every 15 minutes for 1 hour. Statistical analysis, taking into account the difference in average fish weight between the two diets, showed that fish fed the PM diet had higher mortality (90%) than those fed the FM diet (68%)(P = 0.05).