Standardization of broodstock management of ruifish (Labeo rohita Hamilton, 1822) for quality seed production in Bangladesh

Abstract

The overall objective of the study was to improve some aspects of broodstock management practices in the country with a view to produce quality seeds of rui fish (L rohita). Specifically, the study investigated the effects of broodfish sources, feed, and feeding frequencies and rates on breeding performances in terms of fecundity, incubation period, hatchability, fry and fingerling survival of the fish under hatchery conditions. In addition, the study also documented the existing practices of broodstock management and breeding performances of rui fish in five hatcheries in Kishoreganj District, Bangladesh. Existing broodstock management and breeding performances of ruifish Five fish hatcheries were surveyed to document existing broodfish rearing and assessing breeding performances. The number brood rearing ponds varied from 4 to15, water depth maintained at 5-8 feet in rainy season and 4-6 feet in dry season; broodfish pond size were 45-183 decimals, and annual seed production ranged from 152 kg-420 kg. Water supply in all hatcheries is made from both surface and deep tube well sources. All the hatcheries produce Indian major carps and silver barb hatchlings. The fish feed used in the hatcheries include handmade, handmade with vitamin pre-mix, less commonly commercial feed. The broodfishes are fed 1-5% of body weight, once or twice daily. The brood pond preparation protocol includes drying, liming, manuring and less commonly use of rotenone, if ponds are not drained. For pond treatment liming is commonly done in all hatcheries and potassium permanganate, zeolite, oxypore and oxyline tablets are also used. The water quality of the ponds varied, in average, among hatcheries, pH: 7.28±1.11- 8.47±1.24; DO: 5.04±1.11- 6.22±0.73 mg/l; ammonia 1.38±0.70 - 2.5±1.12 mg/l; nitrite 2.66±0.94 - 4.72±1.58 mg/l; Nitrate 5.14±1.78mg/L to 8.5±1.57mg/L, TDS 106.46±41.63 -153.42-57.13 mg/l. The average lengths of brood fish used in individual hatcheries ranged from 52.4 ± 5.13 cm and weights from 1.78 ± 0.16kg to 2.38 ±0.72 kg. The fecundity of individual fishes in different studied hatcheries varied from 1243.67 ±43.26 to 1308.4 ± 62.99 eggs/g gonad weight with an average of 1264.29 ±51.78/ g gonad weight and however, no significant differences in fecundity was observed in among between the study hatcheries. Egg diameter of broodfishes bred in different hatcheries fluctuated from 3.16 ±0.05mm to 3.25 ±0.07mm and the observed differences were not significantly different. In average, hatching rates of eggs in different hatcheries ranged between 63.20 ± 26.53 and 80.40 ± 19.88%. In spite of the large variations in hatching rates, the differences were not statistically significant. The average fry survival rates observed in the studied hatcheries varied from 57.20 ±27.51% to 71.20 ±21.03% and again no significant difference was detected. The fingerling growth rates (lengths & weights) in different nursery ponds ranged from 1510±41.83 to 1656.66 ±90.21%and 319.9± 18.25 to 386.56 ±29.81%. Effect of broodfish sources on breeding performances Three groups of broodfishes, originating from Halda River, Brahmaputra River and hatchery bred ruifish, were used in the experimental trial to assess the breeding performances. The lengths of Halda, Brahmaputra and hatchery bred broodfishes were 55.2±2.38 cm, 53.6±2.30cm, 50±2.91 cm and the corresponding weights were 2.52±0.20 v kg, 2.34±0.20 kg and 1.8±0.30kg, respectively. The fecundity of broodfishes varied from 1203.83±21.55 to 1294.67±74.23 eggs/g of gonad, respectively. Among three different sources of brood fishes, the highest fecundity (1294.67±74.23eggs/g of gonad) was estimated for Hatchery reared broods and the lowest (1203.83±21.55 eggs/g gonad) was found in Halda River broods and the difference was found statistically significant (P <0.05). The highest egg diameter was observed in broods of Hald River (3.31±0.09mm), followed by Brahmaputra broods (3.25±0.56mm) and the lowest (3.18±0.04 mm) from hatchery origin broods, and significant difference in egg diameter was observed between broods from Halda River and that of hatchery origin broods (P<0.05). The hatchability of eggs of broodfishes from three different sources varied greatly, the lowest in hatchery produced (71.20±17.46%) and the highest (89.80±3.11%) in Halda River broodfishes, while that of Brahmaputra River broods was 85.20±9.04%. The observed differences were statistically insignificant (P>0.5). The survival rates of fish fry found were 69.20±18.46%, 78±18.32 % and 81.80±10.03% in hatchery produced, Brahmaputra River and Halda River brood fishes, respectively. However, these differences were insignificant. The growth rate (lengths &weights) of fingerlings produced from three different sources of broodfish were 1403.33± 157.40%, 1660±93.24%, 1673.33±120.53%, and 293.23± 27.88%, 379.9±50.56%, 393.23±76.01% in hatchery produced, Brahmaputra and Halda River broodfishes, respectively, and significant difference was observed in growth rates of fingerlings produced from broodfishes of different sources. Effects of different feed types on breeding performances of rui fish. Three different feed types, viz. handmade feed without vitamin premix, handmade feed with vitamin premix and commercial feed from market, were fed to broodfishes only of Halda River origin. The average body length of fish group fed handmade was 60.4±1.67cm and that of fish fed handmade feed with vitamin premix had a length of 60.8±1.09 cm, while the fish fed commercial feed gained an average length of 62.2± 0.83 cm and the average corresponding body weights were 3.46±0.37kg, 3.34±0.33 kg and 3.56±0.28 kg, respectively. The highest fecundity (1297±73.56 eggs/g gonad) was found in fish fed handmade feed, followed by fish fed handmade feed with vitamin premix (1223.40.±51.63 eggs/g gonad) and fish fed commercial feed (1210.17±20.96 eggs /g of gonad). On the other hand, the highest average gonad weight (670g /fish) was found in fish fed commercial feed, while the lowest weight (646g/fish) was recorded for fish fed handmade feed. Significant difference only found between fish fed commercial feed and that fed with handmade feed. The highest average egg diameter (3.31±0.11 mm) was observed in fish fed market feed, followed by handmade feed with vitamin premix (3.28±0.05mm) and handmade feed (3.18±0.06 mm). However, no significant difference in egg diameter between different treatment groups could be detected (P<0.05). The hatching rates of eggs obtained from different broodfishes fed three types of feed varied greatly, being the lowest (70±18.6%) in fish fed handmade, followed by handmade feed with vitamin premix ((81.8±10.49%) and fish fed commercial feed (85.20±4.66%). Statistically significant difference was found between fish fed handmade and Commertial feed. The highest survival rates fish fries produced from broodfish was found in fish fed commercial feed (75.40±9.10%), vi followed by handmade feed with vitamin premix handmade feed were 72.80±16. the lowest survival rate (65.40±15.57%) was found in broodfish fed. However, significant difference was found between the fish groups fed with commercial feed from market and handmade feed (P=0.05). Fingerling growth rates (lengths & weights) produced from broodfish fed handmade feed, handmade feed with vitamin premix and fish fed with commercial feed were 1660± 41.83, 1686.66 ± 27.38 and 1706.66± 70.31 % and 359.9 ± 43.46, 413.23 ± 50.55 and 457.23 ± 50.46%, respectively. The differences in fingerling growth rates were found statistically significant between fish groups fed handmade and commercial feed. Effect of different feeding rates and frequencies on the breeding performances of broodfish This Experiment Trial was conducted with Halda River broodfish fed at different feeding rates (2%, 3% and 5% of fish body weight) and in two feeding frequencies: once and twice daily. A randomized block design with different combinations of feeding rates and frequencies was made. Fish fed with 2% feed of body weight once and twice daily had average fecundity of 1288±52.35 and 1286±54.04 eggs/g gonad, respectively. Similarly, fish fed 3% feed of body weight attained a fecundity of 1219±45.39 and 1218.2±44.88 eggs/g fish, respectively, while that of fish fed 5% feed, once or twice daily, contained 1193±16.71 and 1192±18.40 eggs/g fish, respectively. A Two-way ANOVA revealed a significant effect of feeding rates (<0.05), while feeding frequency or combined action of feeding rates and frequency showed no significant effects, and no trend in results was evident on the combined effect of feeding rates and feeding frequencies on fecundity of brood fish. The average egg diameter of fish fed 2% feed once and twice daily were 3.3±0.04 mm and 3.3±0.05 mm, respectively and fish fed 3% feed had diameter of 3.31±0.13 and 3.31±0.13 mm, respectively, while fish fed 5% feed once and twice daily had 3.21±0.03 mm and 3.22±0.03mm egg diameter, respectively. Two-way ANOVA performed on the egg diameter data shows that only feeding rates had a significant effect (P=0.05) on egg diameter of fish. Fish fed 2%, 3% and 5% feed of body and once daily had hatching rates of 73.2±4.55, 87.2±10.80 and 71.2±6.53%, respectively, while fish fed twice daily had 72.2± 8.35, 90.0±6.25 and 88.4±8.14% hatching rates, respectively. As revealed by Two way ANOVA that both treatments (feeding rates and feeding frequencies) as well as the combined effects of the treatments have significant effects on the hatchability of eggs. The fry survival rates of fry produced from broodfish fed 2%, 3% and 5% feed once daily showed, in average, 57±5.29%, 65.0±3.0% and 62.0±3.54% survival, respectively, and that of broodfish fed twice daily had 71.2±12.21%, 83.6±8.64± and 88.0±14.22% fry survival, respectively. Two-way ANOVA shows that these effects are significant for both treatments, however, interactive impacts of the combination of the treatments was not evident. The water quality of all broodfish ponds monitored during all experimental trials. The measured parameters varied greatly among ponds and experimental treatments. The average pH varied from 7.58±0.49 to 8.47±1.24; dissolved oxygen (DO) from vii 5.62±0.43mg/l to 5.93±0.62mg/l; ammonia from 0.68 to 2.85 mg/l; nitrite (NO2) from 0.68 to 2.3mg/l; TDS from 115.40±24.22 mg/L to 132.43±25.97 mg/L and nitrate (NO3) from 4.12 to 5.84±1.21mg/l These high fluctuations in the measured parameters were caused mainly due to some abnormal data from some ponds. The study recommend to use brood fish of Halda River origin and raise with commercial feed from market at feeding rate of 3% twice daily.