|dc.description.abstract||The evaluation of the live attenuated vaccine AQUAVAC ESC® in field conditions as well as the use of a primary nursery phase were studied to determine if better production and survival of fingerlings were obtained. This was followed by a
laboratory study to evaluate the vaccine under better controlled environment.
Twenty-five 0.04-ha earthen ponds were stocked with channel catfish fry at a rate of 247,000 fry/ha and grown for five months in one of five treatments: (1) 10-d post-hatch (PH) fry were sham vaccinated and stocked into ponds; (2) 10-d PH fry were vaccinated and stocked into ponds; (3) 10-d PH fry were sham vaccinated, kept in a primary nursery phase for 22 d and then stocked into earthen ponds; (4) 10-d PH fry were vaccinated, kept in a primary nursery phase for 22 d and then stocked into ponds; (5) 10-d PH fry were sham vaccinated, kept in a primary nursery phase for 22 d, vaccinated at that time and then stocked into ponds.
Fingerling mean standing crop ranged from 4,716 kg/ha in treatment 2 to 8,112 kg/ha in treatment 5. A significant difference by treatment occurred only between treatment 2 (4,716 Kg/ha) and treatments 3, 4, and 5 (6,653, 6,910, 8,112 kg/ha, respectively). Individual fish mean weight ranged from 38.8 g in treatment 2 to 40.9 g in treatment 5, and feed conversion ratios (FCR) ranged from 1.15 in treatment 5 to 1.51 in treatment 2. No significant differences, in average weight and FCR were observed between any of the treatments. Mean survival ranged from 47.5 % in treatment 2 to 73.4 % in treatment 5. Significant differences were observed between treatment 2 (47.5 %) and the other three treatments as well as between treatment 3 (60.7 %) and treatment 5 (73.4 %). Mean observed mortality ranged from 1.5 % in treatment 5 to 6.8 % in treatment 2, no significant differences were observed between any of the treatments.
In the laboratory study, mortality ranged from 8 % in treatment 4 to 19.9 % in treatment 2. No statistical differences were observed between any of the treatments.
The proper evaluation of the vaccine was difficult because the presence of mixed infections of ESC and Columnaris disease made it impossible to determine which of the two diseases was responsible for the mortality of fish collected during a documented disease outbreak. A primary nursery phase to hold catfish fry for 32 days before stocking into ponds can be very useful in increasing fingerling yield and survival. Higher survival and final standing crop obtained from the nursery system can reduce space and other resources needed to produce a target quantity of fingerlings hence enabling producers to utilize the space and resources in other more profitable ventures.||en_US