​Early Weaning of Asian Stinging Catfish, Heteropneustes fossilis (Bloch) Larvae

Background: Heteropneustes fossilis commonly known as stinging catfish is a popular indigenous fish of the Indian sub-continent. The species has a high consumer demand because of its tender flesh, low fat and high iron content, and is recommended for anaemic patients. Although the species has high consumer preference and potential for commercial aquaculture but, high mortality of larvae and difficulties in accepting compound diet during larviculture are some of the major bottlenecks. Keeping this in mind, the present study was designed to determine the earliest age at which stinging catfish can be weaned to an artificial diet. The information generated from the present study would be very helpful in improving survival during larval rearing. Methods: The larvae were randomly distributed @ 60 larvae/ tank in 21 circular FRP tanks containing 30 L water each and the feeding experiment started at 2 dph. Seven different feeding strategies depending on the type of food (zooplankton, Artemia nauplii, or microdiet) and the age at which those food items were provided to larvae, were evaluated. Result: The results indicated that larvae survival in the groups weaned after 5 days post hatch (dph) was similar to that of those fed solely with Artemia nauplii and zooplankton, although growth of larvae in the weaned groups was less. As larval growth can be compensated at later stages of the rearing process, therefore, larval survival is considered as one of the most important parameters for evaluating the weaning success. Based on the present findings, it is suggested to rear stinging catfish larvae with zooplankton without dependence upon costly Artemia nauplii, and larvae may be weaned to artificial diet after 5 dph. The findings would be very helpful for improving larval rearing of this indigenous catfish species in Indian rural areas.

Evaluation of Antagonism Activity and Control of Vibrio alginolyticus in Artemia Culture Using Mixed Probiotic

Supplementation with mixed probiotic in aquaculture has been proven to benefit the hosts as disease resistance tool. In this study, a mixed probiotic which consisted of three isolated strains (Lysinibacillus fusiformis strain SPS11, A2, and Bacillus megaterium strain I24) was formulated for the in vitro assays against Vibrio alginolyticus and in vivo preliminary study towards Artemia nauplii. These strains showed antagonism activities against V. alginolyticus in in vitro assay. An increase in biofilm formation of this mixed probiotic was observed which indicated that the strains could work synergistically with each other to confer benefits to the hosts. Enrichment of Artemia nauplii with the formulated mixed probiotic was done to investigate its role in enhancing resistance against the V. alginolyticus. Artemia nauplii were cultured in two different concentrations of mixed probiotic (106 and 108 CFU mL-1) and challenged via immersion method. The mixed probiotic at both concentrations resulted in significantly higher survival of Artemia compared to the challenged group with no probiont added (106 CFU mL-1, 65.00 ± 0.00 % and 108 CFU mL-1, 77.50 ± 3.53 %). Significant reduction of Vibrio loads was observed in Artemia and its culture water supplemented with mixed probiotic at 108 CFU mL-1 whereas there was no reduction of Vibrio at 106 CFU mL-1. This study suggests that the usage of formulated mixed probiotic at high concentration (108 CFU mL-1) as opposed to single-strain probiotic can confer protection against V. alginolyticus infection towards Artemia.