Mixed-sex Nile Tilapia Research Articles

Comparable to 17α- methyl testosterone, dietary supplements of Tribulus terrestris and Mucuna pruriens promote the development of mono-sex, all-male tilapia fry, growth, survival rate and sex-related genes (Amh, Sox9, Foxl2, Dmrt1)

To evaluate Tribulus terrestris and Mucuna pruriens for inducing all-male tilapia, mixed-sex Nile tilapia, Oreochromis niloticus, (mean weight 0.025 ± 0.009 g; mean length 1.25 ± 0.012 cm), were given a meal supplemented with either T. terrestris powder (commercial fish feed, 40% crude protein) (TT group), M. pruriens seed extract (MP group), MP + TT (mixed group), 17α-methyl testosterone (MT, control positive), or without supplements (control negative). The MP extracts significantly increased (P < 0.05) the final weight, weight gain, weight gain rate, and specific growth rate while feed conversion ratio was significantly decreased (P < 0.05). Plant extracts markedly improved (P < 0.05) the survival rate, proportion of males, and total testosterone compared to control and MT. Estrogen levels were lower in groups with plant extract than other groups. Fifteen days post-feeding, the Amh gene was expressed in the brain of O. niloticus fries with higher levels in MP, TT, and MT groups. Additionally, the expression of the Sox9 and Dmrt1 genes as a male related genes in fish fry gonads revealed significantly (P < 0.05) higher levels in groups fed on MP, TT, and MT compared to control after 30-day post-feeding, whereas; Foxl2 gene expression as a female related gene was significantly (P < 0.05) lower in fish fed on MP, TT, and MT compared to other groups after 30 days post feeding. Histologically, MT, MP, TT, and the mixture all exhibited solely male reproductive traits without noticeable abnormalities. This study concluded that each of the TT or MP extracts can induce sex reversal in tilapia while having no negative health impact compared to MT as the growth and survival rate in the treated groups with TT and MP were higher than control and group treated with MT.

Evaluating the growth performance of all male sex reversal and mixed ser tilapia (Oreochromis niloticus) cultured in earthen ponds in Binh Phuo province, Vietnam

The study was conducted to evaluate the growth performance, survival rate and yield of all male sex reversed and mixed sex Nile tilapia (Oreochromis niloticus) cultured in earthen ponds for 180 days. The reversed sex and mixed sex fingerlings (mean weight 7.43 ± 0.35 g) was randomly stocked in six earthen ponds (1,000 m2/pond). The stocking density maintained was 5 fish/m2. The stocked fish were fed a commercial pellet feed containing 35% crude protein. The feeding rate was adjusted according the size of fish, 5% at the beginning to 3% at harvest. Water environment parameters including dissolved oxygen (DO) (4.3 ± 0.8 mg/L), temperature (30 ± 0.7°C), NH3 (0.18 ± 0.2 mg/L), and pH (6.9 ± 0.5) were always within the appropriate range for the normal growth and development of tilapia. The growth rate of sex reversed tilapia was significantly higher (P &lt; 0.05) than that of mixed tilapia throughout the experiment. The harvest weight and length of reversed sex tilapia were 410.5 ± 5.15 g and 25.48 ± 0.48 cm, respectively, and were significantly higher than that of mixed sex tilapia (P &lt; 0.05). The survival rates and feed conversion ratio (FCR) of mono and mixed sex were 90.1% and 89.9%, respectively, but no significant differences were observed (P &gt; 0.05). The relationship of fish lengths and weights expressed by power function revealed that the slope of the length weight regression lines was normal for reversed sex (2.72) and mixed sex Tilapia (2.93) with the high correlation coefficient (&gt; 0.9). The findings of this study demonstrate that reversed sex tilapia has better growth performance compared to mixed sex tilapia. Therefore, reversed sex fingerlings should be used in commercial farming to increase tilapia production.

Effect of Probiotics and Dietary Levels of Protein on Growth, Muscle Quality and Expression of Some Immune Genes in the Head Kidney of Nile Tilapia (Oreochromis Niloticus)

This study evaluated the effect of dietary probiotics (P) to enhance the feed quality, growth parameters, muscle fatty acid (FA) profile, immunity, and the stimulation of immune genes in head-kidney of Nile tilapia. Healthy mixed-sex Nile tilapia (47.0 ± 2.07 g mean weight), were fed three tilapia commercial feeds; S, A, and a local feed K having 33.3, 32.4, and 13.4% protein, respectively. Dietary supplementation of Bacillus probiotic (P) into the commercial feeds resulting in six experimental feeds (S, SP, A, AP, K, and KP) were used. The non-probiotic feeds served as controls and each treatment had three replicates. Results showed that fish fed the SP feed had the highest (P&lt;0.05) final mean weight (582.7 g), daily growth rate (2.52 g/fish/day), gross fish yield (44.0 kg/m3), and best feed conversion ratio (1.9), followed by S (570.4 g, 2.46 g/fish/day, 41.1 kg/m3, and 2.09, respectively). However, these values were the lowest (P&lt;0.05) in tilapia fed KP and K (362.8 and 366.7 g, 1.48 and 1.49 g/fish/ day, 27.4 and 26.8, kg/m3, 2.16 and 2.18, respectively). The feed A and AP had intermediate values. Fish fed the SP feed had the highest (P&lt;0.05) muscle ∑n-3 fatty acid (10.5) and ∑n-3/n-6 ratio (0.75). In general, gut bacterial counts, lysozyme activity, phagocytic activity, and hemagglutination titer were the highest (P&lt;0.05) in tilapia fed the SP, followed by tilapia fed AP, but it was the lowest for tilapia fed K and the KP feeds. Probiotics significantly up regulated β-actin, IgM, IL-β1, Mx, and TNF-α immune gene in the head kidney with better response in fish fed the SP feed. It can be concluded that improvement in tilapia growth, bacterial colonization, muscle quality, immune parameters, and the up regulation of immune genes in the head kidney due to probiotic supplementation would depend on the protein level of the feed used.

Length-weight relationships and condition factors of mono- and mixed-sex Nile tilapia (Oreochromis niloticus) in open water cage culture system

The current study compared the length-weight relationships and condition factors in mono- and mixed-sex Nile tilapia (Oreochromis niloticus). The trial lasted for 91 days and included two treatments with five replications for each, all with the same stocking density. During the study period, 20 randomly selected fish individuals were measured and recorded from each cage every two weeks. The observed growth trend was allometric, with no significant difference in the mean exponential values (b), 2.696 and 2.65 for mono and mixed-sex tilapia respectively. There was a significant difference in final weight gain between monosex (171.58±7.39 g) and mixed-sex (149.09±4.14 g) tilapia. There was no significant difference in final length between monosex (19.80±0.42 cm) and mixed-sex (19.80±0.42 cm) tilapia. Moreover, the mean correlation coefficient (r2) of both groups was positive. The Fulton condition factor (K) also varies from 0.700 to 1.000 (monosex) and 1.000 to 1.010 (mixed-sex). The relative condition factor (Kn) for monosex and mixed-sex tilapia ranged from 1.96 to 2.222 and 2.092 to 2.35 respectively, indicated good aquaculture conditions. The present findings will attract fish farmers to mixed-sex tilapia culture by allowing them to lessen hormone administration and expected to boost national fish production through open water cage aquaculture.

Mixed-sex Nile tilapia (Oreochromis niloticus) can perform competitively with mono-sex stocks in cage production

All-male tilapia stocks are widely used by farmers to supply both domestic and international markets with homogenous, large sized fish (500 g+). While a number of strategies are possible, hormonal treatment of fry with 17α-methyltestosterone (MT) is the most common method used by commercial farmers due to its low cost and ease of application. However, contrasting to its current widespread use, the implications of MT in tilapia farming have raised concerns especially from public and environmental perspectives. Therefore, in this study we tested the impact of stocking a mixed-sex fast growing strain of Nile tilapia (Oreochromis niloticus) fry at high density and then grading out females at 4 or 8 weeks intervals during grow-out and compared final production with a standard MT-treated mono-sex system. From a production perspective, the strategies to remove females at 4 or 8 weeks were successful as no differences in harvest weight, survival and feed conversion rate were observed when compared to the MT-treated group. Similarly, no differences at harvest were obtained in terms of external appearance, Fulton's condition factor, gonadosomatic index, fillet yield, fat-somatic index and visceral-somatic index (%) between MT-monosex group and the groups where females were removed (4 or 8 weeks). However, a financial analysis of this approach showed that the additional costs (fry, feed and labour) involved in the mixed-sex strategy resulted in lower profits. This could be mitigated if a proportion of the removed females could be sold at a premium price as potential broodstock. In the model presented, sales of 13% of the removed females for broodfish at current Thai prices, or a premium of at least 8% for non-sex-reversed final product would be sufficient for the mixed-sex system to return a higher profit than the mono-sex system. The latter strategy could also enable further social licence through use of small fish in nutritional and outgrower initiatives.

Growth performance of male monosex and mixed sex Nile tilapia (Oreochromis niloticus L.) reared in cages, Lake Victoria, Kenya

Growth performance of 17 alpha-methyl testosterone treated monosex and hormone untreated mixed sex tilapia was done for a period of 180 days in cages adjacent to Lwanda Disi beach, Lake Victoria, Kenya. Mixed sex Nile tilapia is known for frequent spawning in culture systems, resulting to fish with varied sizes and stunted growth. To attain male monosex fingerlings, the newly hatched fry were sex reversed by feeding them a diet laced with 17-alpha-methyl testosterone hormone for 21 days. Thereafter, the fry were fed 40% crude protein (CP) diet until stocking into cages. Mixed sex fry of same cohort were fed 40% crude protein starter diet until the time of stocking. A total of 6 cages (2×2×2 m) were randomly stocked with 1000 male monosex and mixed sex fingerlings. The individual mean (± SD) weight at stocking was 9.5 ± 0.06 g and 8.8 ± 0.08 for monosex and mixed sex, respectively. The experimental fish were fed starter diet 40% CP at 10% of body weight for the first two months. From the third month till the end of the experiment, the fish were fed 30 CP diet at 3% of body weight. Measurement of fish total length, body weight and selected water quality parameters was done once a month. There was a significantly higher (P < 0.05) mean body weight gain (BWG), specific growth rate (SGR) and condition factor (CF) for male monosex fish. Conversely, Feed conversion ratio (FCR) was significantly higher (P < 0.05) in mixed sex Nile tilapia. Survival rates (%) and water quality parameters did not differ between the groups. Though the mixed sex Nile tilapia did not reproduce in cages they performed poorly compared to male monosex.

Biofloc-based co-culture systems of Nile tilapia (Oreochromis niloticus) and redclaw crayfish (Cherax quadricarinatus) with different carbon–nitrogen ratios

This study aims to evaluate the production performance of biofloc-based co-culture systems of Nile tilapia and redclaw crayfish with varying carbon–nitrogen ratios (C/N). The experiment was conducted for 80 days in plastic-lined ponds with dimensions of 1 x 1 x 0.6 m. Two biofloc systems with two C/N ratios (10 and 15), using molasses as the carbon source and a control system without molasses were compared. Mixed-sex Nile tilapia with an initial average body weight of 7.00 ± 0.25 g were stocked at a density of 30 fish m−2. After 30 days of culture, redclaw crayfish with initial average body weight of 11.50 ± 0.55 g were added to the culture system at a density of 10 crayfish m−2. There were no significant differences in total animal biomass or total weight gain between treatments (P > 0.05). The total feed and overall feed conversion ratio (FCR) differed significantly (P < 0.05) between the biofloc systems and the control. Total ammonia nitrogen (TAN), nitrite nitrogen (NO2−N) and nitrate nitrogen (NO3−N) concentrations in biofloc systems with a C/N ratio of 15 were generally lower than those of other treatments. Dissolved oxygen concentrations decreased with the increase in the culture period in (4.13–4.40 mg L−1). Based on the results of this study, it can be concluded that an increase in the C/N ratio has positive effects on the feed utilization efficiency and water quality in biofloc-based tilapia–redclaw crayfish co-culture systems.

Effects of Partial Substitution of Fishmeal by Crustacean (Callianassa) Meal on the Growth Performance, Feed Efficiency and Survival Rate of Nile Tilapia (Oreochromis niloticus)

The effect of substituting fishmeal with crustacean (Callianassa) meal in the diets of mixed sex Nile tilapia (Oreochromis niloticus) fry (0.2 g) was evaluated. Three isonitrogenous and isolipidic diets were formulated to contain 30% CP and 15% CL where fishmeal was substituted with Callianassa meal at 0, 25 and 50% in diets R1, R2 and R3 respectively. The experiment lasted for 6 weeks. The stocking density was 10 fish per tank in an isolated system and the capacity of each tank was 50L. Each treatment was administered in duplicates and fish were fed three times per day (09h, 13h, and 17h). The daily ration corresponds to 10% of the live weight of the fish during the first 2 weeks and was reduced to 8% and then 6% for the second and last two weeks of the trial period. At the end of the experiment, fish fed on R1 (control) diet and R2 diet (25% fishmeal replacement) had similar final weight (0.62 g), absolute mean weight gain (0.42 g), relative mean weight gain (210 %) and specific growth rate (2.50 %) and were significantly different from the values obtained from those fed on R3 diet (50% fishmeal replacement). R3 diet had the best FCR (1.42) and was significantly different from the values obtained from R1 and R2 diets but the values of the diets were not significantly different. The dry matter content of the initial fish (96.33%) and those of the R1 (94.12%) and R2 (95.71%) diets did not differ significantly but were slightly higher than that of the value obtained from fish fed on R3 diet (91.15). The protein content of the initial fish (49.63%) was significantly lower than the values obtained from fish fed on R3 diet (61.95%), R1 diet (54.74%) and R2 diet (52.59%). The fat content of the initial fish (41.51%) was higher than the values obtained when fish were fed on the experimental diets. Among the tested diets, the higher the crustacean meal in the diet, the lower the fat content of the fish muscle. The fat content of R1 (control) diet (29.56%) was slightly higher than the value of R3 diet (24.44%) and slightly lower than R2 diet (32.56%). It is concluded that crustacean meal can replace 25% of fishmeal in the diet of Nile tilapia (Oreochromis niloticus) fry at 0.2 g without any effect on the growth performances and feed efficiency.

Effects of Partial Substitution of Fishmeal by Crustacean (Callianassa) Meal on the Growth Performance, Feed Efficiency and Survival Rate of Nile Tilapia (Oreochromis niloticus)

The effect of substituting fishmeal with crustacean (Callianassa) meal in the diets of mixed sex Nile tilapia (Oreochromis niloticus) fry (0.2 g) was evaluated. Three isonitrogenous and isolipidic diets were formulated to contain 30% CP and 15% CL where fishmeal was substituted with Callianassa meal at 0, 25 and 50% in diets R1, R2 and R3 respectively. The experiment lasted for 6 weeks. The stocking density was 10 fish per tank in an isolated system and the capacity of each tank was 50L. Each treatment was administered in duplicates and fish were fed three times per day (09h, 13h, and 17h). The daily ration corresponds to 10% of the live weight of the fish during the first 2 weeks and was reduced to 8% and then 6% for the second and last two weeks of the trial period. At the end of the experiment, fish fed on R1 (control) diet and R2 diet (25% fishmeal replacement) had similar final weight (0.62 g), absolute mean weight gain (0.42 g), relative mean weight gain (210 %) and specific growth rate (2.50 %) and were significantly different from the values obtained from those fed on R3 diet (50% fishmeal replacement). R3 diet had the best FCR (1.42) and was significantly different from the values obtained from R1 and R2 diets but the values of the diets were not significantly different. The dry matter content of the initial fish (96.33%) and those of the R1 (94.12%) and R2 (95.71%) diets did not differ significantly but were slightly higher than that of the value obtained from fish fed on R3 diet (91.15). The protein content of the initial fish (49.63%) was significantly lower than the values obtained from fish fed on R3 diet (61.95%), R1 diet (54.74%) and R2 diet (52.59%). The fat content of the initial fish (41.51%) was higher than the values obtained when fish were fed on the experimental diets. Among the tested diets, the higher the crustacean meal in the diet, the lower the fat content of the fish muscle. The fat content of R1 (control) diet (29.56%) was slightly higher than the value of R3 diet (24.44%) and slightly lower than R2 diet (32.56%). It is concluded that crustacean meal can replace 25% of fishmeal in the diet of Nile tilapia (Oreochromis niloticus) fry at 0.2 g without any effect on the growth performances and feed efficiency.

Effect of Different Rates on Growth Performance, Feed Utilization and Body Composition for Mixed Sex Nile Tilapia (Oreochromis Niloticus) Reared in Tanks

Effect of Different Rates on Growth Performance, Feed Utilization and Body Composition for Mixed Sex Nile Tilapia (Oreochromis Niloticus) Reared in Tanks

EFFECT OF DIETARY PROTEIN LEVELS AND SEX ON GROWTH PERFORMANCE, FEED UTILIZATION AND BODY COMPOSITION OF NILE TILAPIA (OREOCHROMIS NILOTICUS) FRY CULTURED IN HAPS.

The effect of dietary protein levels (35%, 40% and 45%) on growth, survival, feed utilization and body composition of mono sex and mixed sex of Nile tilapia; Oreochromis niloticus L. fry was investigated. Fish were fed frequently to satiation for 7 days a week for 56 days. Results showed that fish growth was significantly affected by protein level. The highest growth performance of fry were obtained with 45% protein diet and the poorest one was obtained with 35% protein diet in both mono and mixed sex Nile tilapia, Oreochromis niloticus fry. Mono sex tilapia were reared in hap in earthen pond showed the highest weight gain, specific growth rate, feed conversion ratio, feed efficiency and protein efficiency ratio, while mixed-sex tilapia showed the lowest weight gain, specific growth rate, feed conversion ratio, feed efficiency and protein efficiency ratio. In conclusion, it was found that 45% crude protein had the highest growth performance parameters, feed utilization and economical evaluation for mono sex Nile tilapia (O. niloticus) fry under this experimental condition.

Aspilia mossambicensis and Azadirachta indica medicinal leaf powders modulate physiological parameters of Nile tilapia (Oreochromis niloticus)

Growing mixed-sex Nile tilapia, Oreochromis niloticus in earthen ponds to table size is a major challenge due to its early maturity and prolific breeding. This study determined the effects of two medicinal plants; Aspilia plant, Aspilia mossambicensis and Neem tree, Azadirachta indica on hatchlings production, growth performance, feed utilization, survival and haematology of O. niloticus. Experimental diets were prepared by adding 1.0, 2.0, 4.0 and 8.0 g of either A. mossambicensis or A. indica leaf powders into a kg of the control diet subsequently administered daily to twenty triplicates of O. niloticus for three months. Both A. mossambicensis and A. indica leaf powder at the used doses, reduced significantly hatchlings production of O. niloticus when compared to the control (P < .05). The lowest value of hatchlings count was found in A. indica dose 8.0 g kg−1 (P < .05). The use of A. mossambicensis leaf powder at a dose of 4.0 g kg−1 improved significantly growth performance and feed utilization (P < .05). In contrast, survival rate was not affected significantly by the two plants (P > .05). Both plants differentially increased significantly haematological parameters such as Hb concentration, packed cell volume (PCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), white blood cells (WBC), monocyte and lymphocytes while reduced significantly neutrophils and eosinophils (P < .05). In conclusion, A. mossambicensis and A. indica leaf powders control prolific breeding of O. niloticus, modulate its growth performance and feed utilization. The two plants also modulate haematological parameters of O. niloticus indicating immunological response towards stress or intoxication, however, the values obtained were not beyond the recommended range for healthy fish.

Growth performance of mixed sex Nile tilapia in cage monoculture and polyculture with African catfish and African carp

Cage culture has been proposed as an option to solve the problem of excessive recruitment and stunting in mixed sex Nile tilapia culture. An experiment was set up in a completely randomized design (CRD) for 4 months to assess the growth performance of mixed sex Nile tilapia in monoculture, biculture, and polyculture with African catfish (Clarias gariepinus, Burchell 1822) and African carp (Labeo victorianus, Boulenger 1901) in cages. Treatment 1 (T1) (control) was a 100% monoculture treatment of Nile tilapia, T2 had a 1:1 combination treatment of Nile tilapia and the African catfish, T3 had 1:1 combination treatment of Nile tilapia and African carp, and T4 had a 5:3:2 combination of Nile tilapia, African catfish, and African carp, respectively. The results revealed that there were no significant differences (p > 0.05) in the growth parameters of Nile tilapia when monocultured, bicultured with each of the two species of fish, and when polycultured with both of them. However, there were significant differences in the survival rates (p < 0.05). The final weight (g) achieved were 32.59 ± 8.75, 36.58 ± 7.29, 34.16 ± 7.73, and 32.02 ± 9.00, respectively. The mean weight gain (g) for Nile tilapia monocultured, bicultured with each of them, and when polycultured with both in cages were 25.07 ± 0.62, 29.86 ± 3.04, 25.91 ± 4.98, and 25.05 ± 2.23, respectively. There were significant differences (p < 0.05) in the condition factors of Nile tilapia in the different species combination treatments. Nile tilapia bicultured with African carp had relatively higher growth rates showed isometric growth and a better condition factor than the rest.

Genotype by environment interaction for harvest weight, growth rate and shape between monosex and mixed sex Nile tilapia (Oreochromis niloticus)

In Kenya, Nile tilapia (Oreochromis niloticus) is mostly grown in ponds. To avoid excessive reproduction and stunted growth, fingerlings are treated with methyl-testosterone to make all-male populations (monosex). For a national breeding programme that aims to provide genetically improved broodstock to hatcheries that supply monosex fry to smallholder pond farmers, it is important to assess the genetic correlation (rg) for traits between the mixed sex breeding candidates from the breeding nucleus and monosex production fish. The purpose of the study was to estimate genetic parameters for harvest weight (HW), daily growth coefficient (DGC) and body shape and investigate genotype by environment interaction (G×E) for these traits between mixed sex and monosex populations. Forty-eight sires and 76 dams from the F2 generation of a local O. niloticus strain, kept at Sagana Aquaculture Research Station, Kenya were used to produce 76 full-sib families. Mixed sex fry (3days old) from each full sib family were divided into two groups of 50 individuals each. One group (monosex) was fed a diet treated with methyl-testosterone to induce sex reversal while the other group (mixed sex) was reared on a control diet. After hapa rearing, tagging and weighing, fish were randomly divided and stocked in six earthen ponds, three for mixed sex and three for monosex fish. After 5months, fish were harvested, photographed and weighed. Genetic parameter estimates for HW, DGC, and shape were obtained on 2105 fish. Heritability estimates for HW, DGC and shape were 0.21±0.03, 0.26±0.04 and 0.12±0.03 for mixed sex respectively. Genetic correlations for HW between monosex and mixed sex was 0.74±0.14, suggesting low G×E. The corresponding rg for DGC and shape were lower; 0.59±0.10, and −0.19±0.11, respectively, denoting the presence of G×E. It is concluded that G×E between the mixed sex nucleus and monosex production fish is important, and that a breeding programme for Nile tilapia needs to include production performance from monosex siblings. Statement of relevanceFirst study that reports estimates for Genotype by treatment interaction between hormone treated monosex Nile tilapia and mixed sex Nile tilapia, and discusses the consequences for nucleus breeding programmes.

Effect of initial stocking size of the predatory African sharptooth catfish (Clarias gariepinus) on recruits, growth performance, survival and yield of mixed-sex Nile tilapia (Oreochromis niloticus) in concrete tank culture system

Prolific breeding and production of high percentage of recruits are main problems in mixed-sex Nile tilapia (Oreochromis niloticus) culture in earthen ponds. The current study assessed the efficiency of different sizes of African sharptooth catfish (Clarias gariepinus) in controlling recruitment in mixed-sex Nile tilapia cultured in tanks and its effect on growth performance, percentage survival and yield. Three treatments consisting of triplicate ponds stocked with mixed-sex Nile tilapia in monoculture and in polyculture with large (62.50 ± 3.26 g) and small (40.00 ± 2.68 g) African sharptooth catfish were fed on a 297.50 g kg−1 crude protein diet for 126 days. Results showed that, the number of recruits was significantly lower in larger African sharptooth catfish predator than smaller ones and monoculture of Nile tilapia. Polyculture with larger African sharptooth catfish resulted in significantly higher growth performance of Nile tilapia. Large African sharptooth catfish in polyculture reduced the amount of small, low-value recruits, while the yield of large and high value Nile tilapia was increased. This study revealed that fish farmers can reduce prolific breeding, obtain higher growth performance and produce larger size of marketable Nile tilapia by predominantly stocking ponds with large African sharptooth catfish predator of at least 60 g.

COMPARATIVE GROWTH PERFORMANCE OF MALE MONOSEX AND MIXED SEX NILE TILAPIA (Oreochromis niloticus L.) REARED IN EARTHEN PONDS

Comparative growth performance of male monosex and mixed sex Nile tilapia (Oreochromis niloticus ) was conducted in six earthen ponds each measuring 150 m 2 at the Kenya Marine & Fisheries Research Institute (KMFRI), Kegati Aquaculture Research Station. Male monosex and mixed sex of O. niloticus juveniles at an average weight of 12.2 ± 0.02 g and average length of 7.6 ± 0.02 cm were collected from nursery production ponds. The male monosex juveniles were obtained by feeding newly hatched juveniles with feed dosed with 17 α methyl testosterone hormone for a period of one month. Stocking was at 3 juvenile

Comparative Growth Performance of Mono-sex and Mixed-sex Nile Tilapia (&lt;i&gt;Oreochromis niloticus&lt;/i&gt; L.) in Pond Culture System at Sebeta, Ethiopian

Comparative growth performance of hand-sexed male mono-sex and mixed-sex Nile tilapia ( Oreochromis niloticus ) was conducted in six earthen ponds (200 m 2 each) in semi-intensive culture system. Experimental ponds were stocked at a stocking density of 2 fish/m 2 . Fish were cultured for a period of 240 days and fed at a daily rate of 5% of fish body weight. The results of the experiment showed that male mono-sex tilapia showed significantly higher (P<0.05) growth rate (weight, length, DWG, SGR) than mixed-sex group. Generally, male mono-sex fishes reached a larger final individual size (176.20±18.01) g than mixed-sex ((108.20±15.4)g, P<0.05). This difference was more pronounced after the 6 th month during the culture period as the later started reproduction early in the production cycle. Analysis on the economic data indicated that both treatments showed positive net return for the culture periods of 6, 7 and 8 months. However, there was a difference in attaining the optimum net return in culturing Oreochromis niloticus as male mono-sex and mixed-sex. The male mono-sex group attained its optimum net return after 6 months of culture periods, while the mixed-sex group attained after 8 months. Therefore, culturing for extra two months in the later case showed a 32% decline from the optimum net return. Hence growing male mono-sex Oreochromis niloticus for 6 months is profitable under Sebeta, Ethiopia condition.

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

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).

Polyculture of Sahar ( Tor putitora) with mixed-sex Nile tilapia

Sahar ( Tor putitora) is an economically important indigenous fish in Nepal, with major efforts to conserve and propagate the species. It is a predator and may function to control recruitment by naturally produced Nile tilapia ( Oreochromis niloticus) in ponds. Sahar ( Tor putitora) were cultured with Nile tilapia ( Oreochromis niloticus) to evaluate control of tilapia recruitment in aquaculture ponds. Two experiments were conducted to assess the effects of the sahar to tilapia stocking ratio on the recruitment and growth of mixed-sex Nile tilapia. The first experiment was conducted in 100 m 2 earthen ponds at the Institute of Agriculture and Animal Science, Chitwan, Nepal to determine these effects. The second experiment was conducted on farm at Kathar, Chitwan, Nepal to verify the results in working ponds. The on-station experiment had four treatments with three replicates each: tilapia monoculture (T1), 1:16 sahar to tilapia ratio (T2), 1:8 sahar to tilapia ratio (T3), and 1:4 sahar to tilapia ratio (T4). Tilapia were stocked at 2 fish m − 2 (average size 11.3 g), and sahar were stocked at treatment densities (15.2 g average size) in each pond. The ponds were fertilized weekly using diammonium phosphate (DAP) and urea at the rate of 0.1 g P m − 2 d − 1 and 0.4 g N m − 2 d − 1 respectively. Tilapia were fed with a locally made pelleted feed (27% crude protein), at the rate of 2% body weight every other day after attaining a size of 100 g. Results showed significantly increased average harvest size ( P < 0.05) for treatment 2, when sahar were stocked with tilapia compared to the tilapia monoculture. The number of recruits significantly decreased ( P > 0.05) when sahar were stocked, and recruit numbers were inversely proportional to stocking density of sahar. Stocking of sahar reduced tilapia recruitment in a mixed-sex Nile tilapia pond culture system and produced better tilapia growth and production. Stocking at a 1:16 sahar to tilapia ratio gave the best overall performance. The on-farm experiment was composed of three treatments with three replicates each: tilapia monoculture (T1), 1:33 sahar to tilapia ratio (T2), and 1:16 sahar to tilapia ratio (T3). Ponds were fertilized every two weeks with DAP and urea at the same rate as on-station experiment, but there was no feeding. On-farm results showed significantly higher tilapia growth with a 1:33 stocking ratio of sahar to tilapia compared to tilapia monoculture. As with the on-station experiment, the number of recruits decreased with increasing stocking density of sahar. Lower sahar stocking provided higher growth and production of stocked tilapia, though there were fewer recruits at these levels. There might have some growth depression of tilapia at higher sahar stocking densities. Stocking sahar to Nile tilapia at 1:33 showed better overall performance than monoculture but not the 1:16 treatment in terms of Nile tilapia growth, production, growth of sahar and gross income.

Diurnal dynamics of water quality parameters in an aquaculture system based on recirculating green water technology

Recirculating greenwater aquaculture technology is an appropriate method for producing commercial quantities of tilapia in areas where water is scarce. Greenwater systems achieve better fish production, more than 90% water recycling and nutrient utilization. This study was designed to address the diurnal dynamics of certain water quality parameters in greenwater system. Culture tanks were stocked at a density of 40 fish/m3 with mixed-sex Nile tilapia, Oreochromis niloticus fingerlings and fed ad libitum with floating pellets containing 34% protein. The water temperature was kept 28±1ºC, aeration was provided and sludge was collected twice daily. Values of critical chemical parameters in the water were found to be well within the acceptable limits based on diurnal water sampling. @JASEM