EFFECTS OF KEEPING BROODSTOCK BEFORE INJECTION, SHADE PERCENTAGE, FEED UTILIZATION RATE AND STOCKING DENSITY ON ASIAN REDTAIL CATFISH Hemibagrus nemurus FRY REARING
Asian redtail catfish (Hemibagrus nemurus) has highly economical value in Indonesia.. Up to present, the intensive culture of Asian redtail catfish has limited due to the insufficient of the seeds. The present study aimed to investigate the effects of keeping broodstock before injection, providing a shade on the larvae rearing, observing the feed utilization rate on the 20 days old fries and optimal stocking density at fry rearing for improvement of seed availability
Four different temperature were used for keeping broodstock before injection: A (27 + 0,3°C), B (29 + 0,3°C), C (31 + 0,3°C) and D (room temperature). Parameters analyzed were fecundities and ovosomatic indexes. On the shade percentage test, it was applied a completely randomized design (CRD) with three different shade percentages: A (25%), B (50%) and C (75%), each treatment had three replicates. The shade used was PVC pipe with 10 cm length and 3.8 cm in diameter. For optimal stocking density, it was used 3 different densities: A (3 fries/L), B (5 fries/L) and C (7 fries/L), each treatment had three replicates. The 20 day old fries with the initial length 1.5 cm were reared in 40 x 40 x 50 cm aquaria for 40 days. Prior to the growth test on the different fries density, feed utilization rate was observed descriptively per hour after at satiation feeding with artemia. Observation on this parameter based on the percentage of feed remaining in the gut, while the parameter for shade percentage and optimal stocking density were the length growth, daily growth rate, specific growth rate and survival rate. The canibalism occured was also observed. The results showed that the fecundities on asian redtail catfish broodstock were 46,333±9,685eggs and ovosomatic indexes were 14.2±2.87%. On the shade percentage test showed that the specific growth rate was not significantly different between 50 and 75 shade percentage with respective values 6.2±0.04 and 6.1±0.12 % day-1. While on the cannibalism occured, the lowest level was 24.0±1.7 on 75 shade percentage but it showed no significantly different with 50 shade percentage. Asian redtail cathfish fry survival rate at the end of the study showed no significantly different between 50 and 75 shade percentage. The optimum was on 50 shade percentage . While on feed utilization of the 20 days old fries, the results showed that at the three hours after satiation feeding, the percentage of feed on the gut remained 20%. On the diffrent stocking density test, the highest total length growth was (4.3±0.16) cm on the 7 fry/L density and it was significantly different compared with others. While, the daily growth rate was not significantly different between treatments. The highest specific growth rate was 6.6±0.13 % day-1 on the 7 fries/L density but showed no significantly different with 5 fries/L density. Asian Redtail Catfish fries survival rate at the end of the study showed no significantly different between 7 fries/L density and 5 fries/L density. The Optimum density was on C treatment (7 fries/L).