A 20-day 3 ∗ 3 factorial experiment was conducted in 100 L HDPE experimental tanks to investigate the effect of the C/N ratio (10, 15, and 20) and stocking density (3, 4, and 5 spawn L−1) on Gibelion catla spawn nursery rearing in the indoor biofloc system. Rice bran was used as the carbon source for manipulating C/N ratios. Each treatment was stocked with catla spawn of average length (6.7 ± 0.4 mm) and average weight (1.6 ± 0.2 mg). Water parameters showed that increasing the C/N ratio from 10 to 20 significantly (
p
<
0.05
) reduced total ammonia nitrogen (TAN) and nitrite nitrogen (NO2-N) and increased nitrate nitrogen (NO3-N) in the water. The insignificant difference (
p
>
0.05
) and lowest final average length, average length gain, average weight gain, and specific growth rate (SGR) were recorded in C/N ratios of 10 and 15 compared to a C/N ratio of 20. A significant difference (
p
<
0.05
) in survival was observed with the increasing C/N ratio. Increasing the fish stocking density resulted in higher mortality. However, a higher amount of fry produced was observed in the treatments with 3 and 4 spawn L−1. Crude protein content increased significantly (
p
<
0.05
) with the increasing C/N ratio with higher content in C/N 20. No significant difference (
p
>
0.05
) in proximate composition of biofloc was observed in different stocking density groups. In conclusion, the application of the biofloc technology with a C/N ratio of 20 at a stocking density of 4 spawn L−1 could be recommended to increase the production of catla fry in the indoor biofloc system.
Seahorse (Hippocampus kuda,Signathidae) ponies were reared for 15 days at the laboratory of Marine Biological Research Station, Ratnagiri (India) using three types of live food viz Artemia nauplii, rotifers (Branchionus plicatilis) and a combination of both. The experiment was conducted in all glass aquaria (0.30 m x 0.30 m x 0.30 m). Seahorse ponies (10 + 0.27 mm) were stocked at 2 L-1 and fed with nutritional live food ad libitum. After 15 days of rearing, the ponies were counted and their individual lengths and weights were recorded. Significantly higher (P< 0.05) weight gain percentage (128.92 + 1.27%) of seahorse ponies, length gain percentage (57.4 + 0.82%), SGR percentage per day (5.53 + 0.04% day–1) and survival percentage (100%) of seahorse ponies were observed in the combination of Artemia nauplii and rotifers as food compared with Artemia nauplii or rotifer alone. Rotifers as live food resulted in poor growth and survival of seahorse ponies under this experimental condition.
The present study on the effect of green water system with harvested rain water on growth performance of freshwater fish Catla catla. Spawn of Catla with an initial length 5.50±0.04 mm and weight 10.99±0.30 mg were stocked at the rate of 6, 8, 10 and 12 no.l-1 in cement tanks (2x1x1m). The green water system containing live phytoplankton viz., Chlorophyta, Cyanophyta and zooplankton viz., Rotifera, Cladocera, Copepoda and Protozoa were was used. The results of the study indicated that the maximum average length gain was (357.89±3.08%), weight gain (779.53±18.03%), specific growth rate (5.56±0.08%) and survival (45.20±0.13%) and were recorded significantly (P<0.05) at stocking density of 6 spawn l-1 as compared to the other stocking densities. The growth of spawn to fry was observed to decrease with increase in the stocking density. Observations on the water quality revealed that the dissolved oxygen value decreased with an increased stocking density. Whereas, the value of ammonia-nitrogen, nitrite-nitrogen, and nitrate-nitrogen increased with the increase in the stocking density. The study showed that better growth and survival of Catla catla spawn to fry stage with stocking density of 6 spawn l-1 reared for a period of16 days in cement tank. The overall results of this study indicated that green water system with harvested rain water has a potential for rearing fish seeds.
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