EFFECTS OF VITAMIN C ON PERCENT NEURULATION, HATCH, GROWTH, AND SURVIVAL OF HYBRID CATFISH CHALLENGED WITH VIRULENT Edwardsiella Ictaluri

Brian C. Peterson*, Nagaraj G. Chatakondi
 
Warmwater Aquaculture Research Unit
USDA-ARS, Stoneville, MS 38776
brian.peterson@ars.usda.gov

Vitamin C (ascorbic acid) is an essential micronutrient involved in several physiological processes such as growth, reproduction, and immune response.  Requirements of vitamin C during gamete formation and early life stages of catfish are not known.  Ascorbic acid (1 mg/mL/kg BW) was administered intraperitoneally into 3 mature channel catfish (IpC) and saline was administered i.p. to 3 mature channel catfish (IpS).  Eggs from ovulated females were collected and fertilized with blue catfish sperm to produce hybrid embryos.  Eggs were placed into hatching baskets in troughs labelled by treatment.  

Eggs from another 6 hormone-induced channel catfish females were fertilized with blue catfish sperm to produce hybrid catfish embryos.  Fertilized eggs were immersed in an ascorbic acid immersion solution (ImC) or saline (ImS) for 3 hours.  All eggs were rinsed in hatchery water and placed in hatching baskets.  

Percent neurulation, hatch, and survival at 5 and 30 days were recorded.  Two month old fish (3.7 g) from each treatment were then stocked into aquaria (25 fish/tank).  There were 3 replicates/female for a total of 9 tanks/treatment.  After a 2 week acclimation period, a 7 week growth study was conducted.  At the end of the study, fish were group weighed and challenged 2 days later with virulent Edwardsiella ictaluri.  Results showed percent neurulation and hatch were similar among treatments.  Survival at day 5 was higher in IpC and IpS compared to ImC and ImS (P < 0.05).  By day 30, survival was highest in the IpC, IpS, and ImS treatments compared to ImC (P < 0.05).  After feeding the fish for 7 weeks, weight gain was similar among treatments. Survival in fish challenged with virulent E. ictaluri were also similar among treatments.  Results suggest there is no benefit of treating channel catfish broodfish with vitamin C or immersing hybrid catfish eggs in a vitamin C solution.