Heterobranchus longifilis is highly esteemed fish in Africa, but high demand for the depleting natural stock and the deficiency of the fry production, poses major problem to fish farmers. To determine optimum stocking density that will yield highest growth performance in the aquaculture of Heterobrachus longifilis juveniles, 14 days-old fish juveniles were counted and stocked in triplicates, at five densities 2500, 3000, 3500, 4000, and 4500 larva per tank (5 larva/L (D5), 6larva/L(D6), 7larva/L(D7), 8larva/L (D8) and 9larva/l(D9) respectively). The results of the specific growth rate (SGR), mean daily weight gained (MDWG) and performance index (PI), condition factor (CF), survival rate (SR) and biomass showed lower values at higher stocking densities. However, the coefficient of variation (CV) and apparent food conversion ratio (AFCR) increased with stocking density, with highest values at D8 and D9 indicating that, high stocking density reduced feed efficiency and produce poor final biomass. The best values were therefore obtained in stocking density of 6 larvae /L (D5).

The question of adaptation to inert food is the most complex when talking about frog rearing in captivity, because frogs eat exclusively moving preys in natural conditions. The solution is to find a way to make the food attractive so that the frogs will eat it. Some frog-farmers mix the diet with live fly larvae which they reduce progressively until the frogs accept voluntary the inert food. The work reported here examined the effects of this progressive adaptation on performances of the North African green water frog reared in captivity. The results show that after two months of feeding froglets with fodder granules plus live domestic fly larvae, it is possible to eliminate the larvae completely from the frogs’ diet.

Two lipid sources were examined as fish oil replacements in fishmeal free, plant protein based diets for juvenile gilthead sea bream, Sparus aurata. A thraustochytrid meal plus soybean oil (MSC) and a canola oil (CO+EFA) supplemented with docosahexaenoic (DHA) and arachidonic acids (ARA). A twelve week growth trial was undertaken to examine the performance of the diets and to assess whole body and fillet fatty acid profiles resulting from the use of alternative lipid sources was comparable to fish oil. A finishing period was also utilized in an attempt to recover a fish oil fatty acid profile in the fillets of fish fed the alternative lipid source diets. The MSC diet significantly outperformed the fish oil control diet in terms of weight gain, feed conversion ratio, condition factor and protein efficiency ratio while maintaining similar fillet yield while the CO+EFA diet performed similarly to the control diet. Although fatty acid profiles in the whole bodies and fillets at the conclusion of the growth trial were representative of that of the diet fed, transition toward the fish oil profile was observed at the conclusion of the finishing period. Overall, both alternative lipid sources performed equivalently or better than the fish oil control, a significant finding for this species. Low dietary lipid (~7-9%) was just as effective as high dietary lipid input, observed in other studies and did not result in lowered fillet lipid levels or growth performance. As a note taurine had to be supplemented to the plant protein diets.

To improve on management strategy of mochokid catfish, (Synodontis clarias) in the Cross River, biological and biometric data including; stomach content, standard length and total weight of 500 fish were collected monthly, from January, 2009 to December, 2011 and used to investigate the trophic ecology and population parameters. Stomach content showed the fish to be euryphagus and benthic feeder, with inter-seasonal difference in food item. Length-weight relationship was described as W = -3.97 + 0.98 L (male), W = -19.7 + 1.00L (female) and W = -6.73 + 0.99L (combined sex). Condition factor ranged from 0.32±0.7 minimum for males (midriver) to 2.25±0.6 maximum also for males (downriver) with monthly variation for both sexes peaked between June and July, and November and January, with better conditions for males than females. Growth parameters were L∞ = 72.12, 79.23 and 76.34; k = 0.22 year^-1 0.34 and 0.31 for males, females and combined sex, respectively. Index of growth performance (Φ’) = 3.11 (males), 2.65 (females) and 3.78 (combined sex). Longevity potential (t_max) was 30.34, 33.56 and 32.33 years, for male female combined sex, respectively. Z and M were 0.45 year^-1, 0.67 year^-1, 0.55 and 0.24, 0.38 and 0.29 year ^-1 while F, E and E_max values were 0.18, 0.34 and 0.28 years^-1 , 0.66, 0.86, and 0.78) and 0.78, 0.87 and 0.98 for males, females and combined sex, respectively, indicate that overfishing of S. clarias is not occurring in the Cross River (i.e., E < E_max). However, E exceeded E_0.5 (0.29, 0.34 and 0.39) and was not close to E_0.1 (0.54, 67 and 0.66) for males, females and combined sexes, indicating that the present exploitation rate must be maintained for males, females and combined sexes to achieve the optimum yield per recruit.

The length-weight relationship of carps was studied in Raipur reservoir, Gwalior from April, 2009 to March, 2011. Four major carps species, viz., Catla catla, Labeo rohita, Cirrhinus mrigala and Cyprinus carpio were cultivated in the reservoir. The growth of carps was studied from April, 2009 to March, 2010 during first year, while in second year growth studies were conducted during August, 2010 to March, 2011. In the year 2010-11, however, the reservoir dried up during the period from April, 2010 to July, 2010 due to low rains during the rainy season and high evaporation during the summer. The values of ‘n’ for C. catla, L. rohita, C. mrigala and C. carpio were 2.438, 3.399, 2.844 and 2.358 respectively in this water body during 2009-10, while the values of ‘n’ for C. catla, L. rohita, C. mrigala and C. carpio are 2.856, 2.827, 2.771 and 2.394 respectively were during 2010-11. The value of coefficient of correlation (r) between length and weight shared a perfect positive relationship in all the fishes studied during both the years of study. A total of 200 specimens of each of four species were taken and a logarithmic graph plotted between length and weight has shown a straight line in all the four carps. The condition factor ‘K’ for C. catla revealed that with the progression of growth of the fish, the well being of fish decreased as this factor is showing a decreasing pattern while in L. rohita fish attains good growth and size in comparison to other fishes and a positive pattern of condition of fish was observed. The condition factor ‘K’ for C. mrigala revealed that with the progression of growth of the fish, the well being of fish increased with increased age and in C. carpio a decreasing pattern with the progression of growth in the fish was shown, thus the well being of fish was also low. The absolute growth may be concluded that the growth increment during first year of culture the growth was highest in L. rohita in comparision to other carps while in second year maximum growth was exhibited by C. catla and minimum growth by C. carpio. It was found that rohu had good absolute growth in the reservoir in the first year. However, in second year of study, it was catla who had a little edge over rohu. C. carpio grew the least in comparison to other carps. On the basis of physico-chemical characteristics of the Raipur reservoir, it may be classified as meso-eutrophic one.