Jean-Claude Micha

The effects of dietary crude protein on growth of the Eurasian perch Perca fluviatilis

Abstract A 73-day feeding experiment was conducted to evaluate the effects of dietary crude protein level on growth of Eurasian perch juveniles. Determination of the protein requirement of 2.9 g perch was performed with six semi-purified diets containing crude protein levels ranging from 0 to 60%. Fish were held in three recirculated systems, each diet being tested in triplicate. Significant differences in growth and survival appeared among fish fed diets containing up to 30% crude protein and fish fed diets from 40% crude protein and above. Three mathematical models (the four parameter saturation kinetics, broken line and second order polynomial Brett model) were used to analyse the relationships between dietary crude protein and specific growth rate. According to the saturation kinetics and polynomial models, the optimum dietary crude protein levels were 36.8 and 43.6%, respectively. Based on broken line and polynomial models, maximum growth occured at 43.1 and 56.5%, respectively. Endogenous protein losses of 2.9 g juvenile perch reached 1.11 mg fish −1 day −1 at 23 °C.

Comparative Appetency for Azolla of Cichlasoma and Oreochromis (tilapia)

Abstract In a comparative study of the preferences of two species of fish for different Azolla species (aquatic fern), Cichlasoma fenestratum showed a clear preference for Azolla microphylla while tilapia ( Oreochromis niloticus ) preferred Azolla filiculoides. A. pinnata was neglected.

A Preliminary Assessment of Growth and Production of Nile Tilapia, Oreochromis niloticus L., Fed Azolla-Based-Diets in Earthen Ponds

ABSTRACT The effects of the use of Azolla filiculoides Lam., as an alternative source of protein, on growth performances and production of Nile tilapia, Oreochromis niloticus, reared in wetland ponds was evaluated. Three isonitrogenous (27% CP) and isocaloric (4019.14 kcal/g) diets A0, A10, and A20 containing three levels of Azolla 0, 10, and 20, respectively, as a partial substitution of fish meal, were fed to three triplicate ponds of male O. niloticus (initial mean weight = 15.5 g). The Azolla-free diet (0% Azolla) served as a control. The growth performances and production are good in all treatments after 90 days of experiment. No significant differences among dietary treatment (P > 0.05) were noticed for daily growth rate (1.15 g/day–1.26 g/day), specific growth rate (2.27–2.35%/day), survival (74.78–77.43%), annual fish production (31.01–32.75 kg/are/year), and feed conversion ratio (1.06–1.13). Thus, similar growth and production performances were observed with fishes fed with A0 and those fed with A20. Therefore, up to 20% of Azolla in the ration of O. niloticus has no negative effect on either growth or production. The cost-benefit analysis showed a considerable reduction in the production costs of one kilogram of fish with increasing Azolla levels in diet, amounting to US

An investigation into the mass production of the freshwater rotifer Brachionus calyciflorus Pallas. 1. An eco-physiological approach to nutrition

0.09 between A0 and A10 (P > 0.05) and US

[Comparaison de la croissance et de la composition chimique d'Oreochromis (Tilapia) niloticus L. et de Cichlasoma (Theraps) melanurum Gth. Nourris avec Azolla]

0.14 between A0 and A20 (P < 0.05). These results indicate that, on an isonitrogenous and isocaloric basis, using Azolla at up to 20% in a diet can constitute a viable alternative source of protein for O. niloticus in tropical wetlands.

Effect of Densities and Culture Systems on Growth, Survival, Yield, and Economic Return of Freshwater Prawn,Macrobrachium rosenbergiiFarming in the Rice Field in the Mekong Delta, Vietnam

Abstract Feeding and production rates of the freshwater rotifer, B. calyciflorus Pallas, were determined during a daily cycle of feeding with the alga Dictyosphaerium chlorelloides or with the yeast Saccharomyces cerevisiae . Filtration and ingestion rates of rotifers decreased significantly during the cycle of feeding. The filtration rate decreased from 4.02 to 1.18 μl/ind. h −1 with the algae and from 2.06 to 0.94 μl/ind. h −1 with the yeast. Production rates of 28 and 17 ind./ml d −1 were achieved, respectively, with algae and yeast. The filtration rate of rotifers was significantly influenced by the cellular density of algae but not by that of yeast. The maximal value (4.04 μl/ind. h −1 ) was obtained at an algal density of 4 × 10 6 cell/ml. With algae, the ingestion rate seemed to reach a maximum between 4 and 8 × 10 6 cell/ml (191 × 10 2 cell/ind. h −1 ) at 5 × 10 6 cell/ml. With yeast, the rotifer ingested a maximum of 86 × 10 2 cell/h. At optimal cellular density and photoperiod (L:D 24:0), the filtration and ingestion rates of rotifers were maximal at 25 °C.

Rearing Rabbits Over Earthen Fish Ponds in Rwanda: Effects on Water and Sediment Quality, Growth, and Production of Nile Tilapia Oreochromis niloticus

Abstract The growth of two species of Cichlidae, the African Oreochromis niloticus and the Central American Cichlasoma melanurum , fed with three different diets (100% pellets, 50% pellets and 50% Azolla , 100% Azolla ) was compared. The growth performances of O. niloticus ( G =2.3) fed only with pellets were higher than those of C. melanurum ( G =0.9). With the mixed diet (50% pellets and 50% Azolla ) growth was reduced for both species but this reduction was proportionally lower with C. melanurum . The fish fed exclusively with Azolla showed negative growth but fish weight loss was least for C. melanurum . Comparison of the chemical composition of the two fish species reveals significant differences. Generally moisture is lower for C. melanurum and lipid concentration is higher for this species with all three diets. Fed with Azolla , both species have a higher moisture and lower lipid concentration. Crude protein concentration (±15%) is very similar for both species regardless of diet. In conclusion, for intensive fish culture based on commercial pellets, the African species O. niloticus performs better than the American C. melanurum . On the other hand, the use of Azolla as feed for these fish does not seem very satisfactory but experiments should be conducted with typical herbivorous Cichlidae which may be able to utilize this fern in agro-piscicultural ecosystems.

Chemical Relationships Between Azolla and Cichlasoma

Abstract Postlarvae of Macrobrachium rosenbergii (de Man 1879) were stocked at 2, 4, and 6 postlarvae (PL)/m2 into rice fields under two culture systems, the integrated and the rotational prawn-rice system. Prawn was fed pellet feed twice daily. The growth of Macrobrachium rosenbergii decreased at higher stocking densities. Prawns in the rotational system grew faster than those in the integrated system. The yields ranged from 286±32 to 516±51, 412±17, to 584±41 kg/ha in the integrated and the rotational prawn-rice system, respectively. The yield at density of 2 PL/m2 was significantly lowest (P < 0.05) and was highest in the treatment with 6 PL/m2. However, at higher density, the investment cost significantly increased (P < 0.05), while profit significantly decreased (P < 0.05). At a density of 2 PL/m2cost benefit ratio and profit was the highest (P < 0.05). The integrated rice-prawn system gives lower profits than the rotational system.

The On-Farm Trials of the Rotational Prawn-Rice Farming in a Semi-Deep Water Area

Nine earthen ponds of 400 m2 each, were stocked with 800 mixed sex Nile tilapia Oreochromis niloticus fingerlings (14 g mean weight stocked at 2 fish/m−2) and fertilized with rabbit droppings from rabbits reared over fish ponds and stocked at three different densities: T1 = one, T2 = two, and T4 = four rabbits per 100 m2 of pond. After 152 days, results from this integrated rabbit/fish system showed: 1) increasing nutrient content of all ponds in the three treatments except for nitrates, which decreased with time and, 2) good water quality in terms of pH, dissolved oxygen, and turbidity. Fish mean weight at harvest and fish yield were higher in ponds fertilized by the highest rabbit stocking rate: 42.32 g and 6.35 ± 1.0 kg/are, respectively (1 are = 100 m2).

Caractérisation et écologie des peuplements des mormyridae dans la réserve de Yoko (Kisangani, RD Congo)

Abstract The selective appetency of Cichlasoma melanurum for various Azolla species is related to the presence in the fern of attractive, methanol-soluble, as well as repulsive, dichloromethane-soluble, substances.