Mixed-sex Nile Tilapia Research Articles

Growth Performance of GMT and Mixed Sex Nile Tilapia Oreochromis niloticus on Natural and Supplemental Feeds

Attention has been focused on genetically-improved stocks and strains of tilapia. A greenhouse recirculating aquaculture system (RAS) of three 540 L tanks stocked with 100 37.2 g genetically male tilapia (GMT) Nile tilapia, Oreochromis niloticus, and three identical tanks with the same number of 38.1 g mixed sex Nile tilapia, was used to measure response to floating 3.0 mm catfish pellets (32 % protein) fed once per day at four different rates based on body weight day-1 (2-4 % BW day-1). Feed rate and amount were changed every 14 days based on growth measurements. For growth comparisons on natural feeds (primarily phytoplankton), two 10.5 m3 net pens were each stocked in August with 105 7.7 g Nile tilapia m-3 of each group in each of two 1.0 ha blue catfish Ictalurus furcatus fingerling ponds and not fed. Fish were harvested in November. GMT fish outperformed mixed sex fish on both feed sources, and at most feed rates. In RAS trials at 2, 2.5, 3.0 and 4.0 % BW feeding, percentage growth day-1 was 1.95, 2.11, 2.21 and 3.31 for GMT, and 1.60, 2.22, 1.97 and 2.86 for mixed sex; and the associated food conversion ratio (FCR) was 1.54, 1.37, 1.37 and 1.04 and 1.64, 1.35, 1.42 and 1.20, respectively. At harvest in net pens, GMT fish were 25 % larger than mixed sex. Growth was 1.3 and 1.0 g day-1 on natural food sources for GMT and mixed sex, respectively.

Economic profitability of Nile tilapia (Oreochromis niloticus L.) production in Kenya

Economic profitability of Nile tilapia production in Kenya was analysed using a model that simulated individual fish growth and took fish population dynamics in the pond into account. The results suggest that the currently practiced mixed-sex tilapia culture is economically unsustainable. It is suggested that research and extension efforts be geared towards developing monosex Nile tilapia production systems. Nile tilapia culture with African catfish predation should be viewed as an intermediate step towards all-male Nile tilapia culture. This will allow accumulation of both physical and human capital to support all-male tilapia culture. Under all-male culture, economic returns are high enough to justify investment in Nile tilapia culture using borrowed capital. However, the success of monosex culture will depend on the availability and affordability of quality fingerlings and low-cost fish feeds. The results have a wide application in Sub-Saharan Africa where mixed-sex Nile tilapia culture is common.

Operation of a Water Recirculating Greenwater System for the Semi-Intensive Culture of Mixed-Sex and All-Male Nile Tilapia, Oreochromis niloticus

Recirculating greenwater aquaculture technology is an appropriate method for producing commercial quantities of tilapia in locations that have water scarcity. Greenwater systems achieve three major goals; higher fish production, maximum water recycling (> 98%) and nutrient utilization. Some nutrients are recycled back in this system to sustain the development of photosynthetic algae and nitrifying bacteria creating a “suspended growth treatment process” that maintains adequate water quality. In this study, the greenwater system was implemented in triplicate, each replicate had a fiberglass fish culture tank and a cone bottomed clarifier for solid filtration. Water from the fish culture tanks is pumped to the cone clarifier through the airlift and the outflows of the cone clarifiers trickled back to the fish culture tanks at a rate of 7–8 L/minute. The study was designed to compare the performance of a greenwater system with mixed-sex, as well as, all-male tilapia. Culture tanks were stocked at a density of 40 fish/m3 with mixed-sex Nile tilapia, Oreochromis niloticusfingerlings and fed ad libitum with floating pellets containing 34% protein. The water temperature was maintained at 28±1°C, intensive aeration was provided and sludge was collected twice daily from the clarifiers. Fish were harvested after six months and culture tanks were restocked for another six months with hand-sexed all-male Nile tilapia fingerlings at a density of 40 fish/m3. Values of critical chemical parameters in the water were found to be well within the acceptable limits based on weekly water sampling. The mean final weight (±SD), final biomass, growth rate, SGR, FCR, and percent survival for the mixed-sex tilapia was found to be 287.09 (94.63) g/fish, 11.25 kg/m31.43 g/fish/day, 1.27%, 1.77%, and 97.92%, respectively. Values for the mean final weight (±SD), final biomass, growth rate, SGR, FCR, and percent survival for all-male tilapia populations were 359.67 (80.69) g/fish, 14.63 kg/m31.75 g/fish/day, 1.29%, 1.64%, and to 98.05%, respectively. Contrasting to the semi-intensive aquaculture in Saudi Arabia where 20–50% of the total water is exchanged daily to produce 8–15 kg fish/m3 of water, 12–15 kg of fish/m3 was produced with addition of only 1% of the total water daily. Only 180 liters of water was consumed to produce one kg of fish in the system.

Impact of nutrition and season on pond culture performance of mono-sex and mixed-sex Nile tilapia ( Oreochromis niloticus)

A 2×2×2 factorial experiment was carried out in a 16 earthen pond system to determine the effect of poor and improved nutrient inputs on the performance of mixed-sex and mono-sex Nile tilapia over both wet and dry seasons in Central Thailand. The poor nutrient level consisted of fresh ruminant manure only (50 kg dry matter ha −1 day −1) and the improved also received inorganic fertilisers and ricebran as supplementary feed. Artificially incubated first feeding hatchlings were nursed under similar conditions to produce mixed-sex and mono-sex fry before stocking in 200 m 2 ponds at 3 fish m −2. Growth and net yields after 5 months were affected by nutrient level but not by sex (mono- or mixed-sex). However, ponds stocked with mixed-sex fish had a significantly greater proportion of small fish (<15 cm TL) than mono-sex that had more large size class fish (>15 cm TL). Mean weights of fish in each size class were not different overall but if ponds with improved nutrition were considered alone, survival and use of mono-sex affected the mean size of recruits (i.e. individuals <10 cm) and stocked fish (10–20 cm) harvested. Individual harvest size was inversely related to survival. The lack of major differences in performance of mono-sex and mixed-sex was linked to the presence of piscivorous fish and the method of seed production. The pattern of survival among the different treatments was possibly related to the movement of the air-breathing fish between ponds. The homogeneous and young age of the mixed-sex seed may explain the relatively low levels of reproduction, indicated by numbers of fry, observed in the trial. The importance of nutrient levels, rather than the use of mono-sex fish in the Chitralada strain, was demonstrated, provided young mixed-sex seed are used. The study has implications for promoting smallholder tilapia production; both the nature of demand for fish and the resource base need to be understood before developing tilapia hatchery strategies.

Effects of Feeding Pelleted versus Non-pelleted Defatted Rice Bran on Nile Tilapia Oreochromis niloticus Production and Water Quality in Ponds

Effects of pelleted versus non-pelleted defatted rice bran on fish production and water quality were evaluated at the Aquaculture Research Station, University of Arkansas at Pine Bluff. Mixed-sex Nile tilapia (Oreochromis niloticus) were stocked at 2.3/m-2. into each of six 0.04-ha earthen ponds. Largemouth bass (Micropterus salmoides) were added at 0.17/m-2 for population control. Defatted rice bran was fed to fish at 2% body weight daily. After 169 days, tilapia harvests averaged 2,924 kg/ha in pellet-fed and 3,031 kg/ha in loose bran-fed treatments (a non-significant difference). Stocked fish comprised an average of 52% and 39%, respectively, in these treatments, and approached a significant difference (P==0.2). Average amounts of inorganic fertilizer required to maintain chloro­phyll a levels of 100-150 mg/m-3 were significantly different at 736 and 1,108 kg/ha in pelleted and loose bran treatments, respectively.

A Preliminary Study on Nile Tilapia (Oreochromis niloticus) Polyculture with Common Carp (Cyprinus carpio) Fed with Duckweed (Spirodela) in Nepal

Mixed-sex Nile tilapia (Oreochromis niloticus) and common carp (Cyprinus carpio) were cultured in four cement ponds of 72 m2 at 1:1 ratio with a stocking density of 1 fish· m·2 during summer in subtropical Nepal. Fish were fed with locally collected duckweed (Spirodela sp.) during 108 days of experimental period. Nile tilapia grew from 39.6±3.7 g at stocking to 145±5.2 g at harvesting with a survival rate of 90±4 %. Common carp grew from an initial 2.8±0.G g to final 63.2±2.4 g with 97±1 % survival rate. The ex­trapolated annual yield of stocked fish ranger.! from 2.3 - 2.9 t•ha·1 with a mean of 2.5 ±0.1 t·ha·1. Tilapia offsprings produced during the experimental period was 1690:±261 fish per pond with an average size of 7.2±1.6 g. Weight of tilapia recruits obtained was two times more than that of the net yield of originally stocked fish. The common carp did not control tilapia recruitments.

Introduction of Sahar (&lt;i&gt;Tor putitora&lt;/i&gt;) in Cage-Cum-Pond Integration System of Mixed-Sex Nile Tilapia (&lt;i&gt;Oreochromis niloticus&lt;/i&gt;)

Introduction of sahar in cage-cum-pond integration system of mixed-sex Nile tilapia was evaluated using 15 outdoor cemented ponds of 24 m2 (4.9m × 4.9m) size with 1.25 m water depth placing a cage of 1.2m× 1m × 1m size holding 1 m3 water at the center of each pond at Institute of Agriculture and Animal Science (IAAS), Rampur, Chitwan, for 158 days. The experiment was conducted in a completely randomized design (CRD) with five treatments replicated thrice. The treatments were: large sized Nile tilapia in cage and small sized Nile tilapia in pond (cage-cum-pond system) (T1); cage-cum-pond system with 2 sahar (T2), cage-cum-pond system with 4 sahar (T3), cage-cum-pond system with 8 sahar (T4) and cage-cum-pond system with 16 sahar (T5). Stocking density of caged and pond tilapia was 1 fish/m2 and 2 fish/m2, and size was 78-90 g and 15-16 g respectively. The feed, containing 20% crude protein, was supplied for caged tilapia at the rate of 2% body weight daily. Mean stocking size, harvest size, survival rate, daily weight gain and net fish yield of both caged and pond Nile tilapia were not significantly different among treatments (p &gt; 0.05). Mean harvest weight and daily weight gain of sahar in treatment 2 was significantly higher than other treatments (p &lt; 0.05). NFY of caged tilapia, pond tilapia and combined fish yield were not significantly different among treatments (p &gt; 0.05). Higher numbers of recruits were observed in control and lowest in the treatment 5 suggesting that higher number of sahar in this system effectively controls the tilapia recruits. This experiment showed that addition of sahar in the cage-cum-pond integration system of Nile tilapia effectively controls the number of tilapia recruits and increase NFY.Key words: cage-cum-pond integration, Nile tilapia, Sahardoi:10.3126/on.v5i1.798Our Nature (2007)5:52-59