Mixed-sex Tilapia Research Articles

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 < 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 < 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 > 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 (> 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.

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 tilapia culture model for sub-tropical Nepal

This datasheet on Mixed-sex tilapia culture model for sub-tropical Nepal covers Identity, Overview, Case Study, Environmental Requirements, Growout Systems, Related Content, Further Information.

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.

Microbial Community Response to Carbon-Nitrogen Ratio Manipulation in Biofloc Culture

Biofloc technology (BFT) is an alternative aquaculture practice that involves the manipulation of carbon-nitrogen ratio (C:N) to manage nitrogenous waste through microbial assimilation. This study aimed to determine the composition of the microbial community present in BFT and describe the microbial community’s response to C:N manipulation. The experiment had a complete randomized design with two set-ups (i.e., BFT and control) in triplicates. The experimental unit was a 120-L rectangular tank stocked with 15 mixed-sex tilapia fish, Oreochromis niloticus, with an average weight of 15±3 g. The C:N was adjusted to 16:1 using molasses. Illumina MiSeq sequencing platform was used, and bioinformatics was conducted in R using dada2 and phyloseq package. Seventeen (17) phyla were identified, but only seven were remarkably abundant, namely: Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Verrucomicrobia, Planctomycetes, and Fusobacteria. Double Principal Coordinates Analysis (DPCoA), Principal Coordinate Analysis (PCoA) of Weighted Unifrac Distance and Canonical Correspondence Analysis (CCoA) revealed an association of Proteobacteria to low ammonia concentration in BFT treatment. On the other hand, phylum Bacteroidetes was clustered towards the control, characterized by high ammonia. Overall, BFT has increased Shannon and Simpson diversity indices compared to the control. Regime change in the microbial community was not easily caused by organic C supplementation because of community robustness to withstand biotic and abiotic disturbances. Controlled laboratory experiment showed that some bacteria species proliferate as a response to C:N manipulation, but established species remained dominant.

Comparative Growth Performance of Genetically Male, SexReversed, and Mixed-Sex Nile Tilapia (Oreochromis niloticus) Reared in Earthen Ponds in Sagana, Kenya

Nile tilapia (Oreochromis niloticus) culture has been faced by challenges of prolific breeding and early maturity of mixed-sex tilapia that can be solved by the culture of all-male tilapia. A study was conducted to compare the growth performance, survival and condition factor of genetically male tilapia (GMT), sex-reversed tilapia (SRT) and mixed-sex tilapia (MST) cultured in earthen ponds. Fingerlings of initial weights ranging from 0.41 to 0.91 g for GMT, SRT and MST were stocked in 150 m2 earthen ponds in triplicates at 3 fish m-2 and fed on a 35% crude protein diet. After 180 days culture period, the final body weights of SRT (202.82±7.30 g) was significantly higher than GMT (174.34±3.71 g) and MST (148.06±4.60 g) (P&lt;0.05). The survival of MST (74.11±4.73%) was higher than GMT (67.22±9.72%) and SRT (65.22±2.94%) but no significant differences were observed (P&gt;0.05). The condition factor of all the fish was above 1 and was significantly different between the groups (P&lt;0.05). This study demonstrates that SRT has superior growth performance than GMT and MST hence sex reversal should be used for improved Nile tilapia production.

Dataset on the production of predominantly male tilapia progeny using two malawian tilapias, Oreochromis karongae and Oreochromis shiranus.

A dataset is presented of an experiment that was conducted to compare the proportions of males obtained from hormonal sex reversed pure strain of Oreochromis shiranus and from interspecific hybridization of O.karongae male x O. shiranus female. Part of the data in the dataset were published in a journal article https://doi.org/10.1016/j.aqrep.2020.100274. The data were generated from four SETs of treatments of an experiment that was conducted at the National Aquaculture Center, in Malawi. The first SET of treatment comprised hybrids from interspecific crossing of O.karongae male and O. shiranus female in a pond based breeding hapa 1. SETs 2 and 4 were for fry from hapa spawned pure cross of O.shiranus males and females in a pond based breeding hapa 2. SET 3 comprised fry from pure cross of O. shiranus males and females under controlled temperature (27°C) in an indoor re-circulatory hatchery (Tables 1 to 4). During the first part of the experiment, the fry was raised for 28 days in tanks at three replicates and was fed a fry formulated feed containing 38% crude protein, three times a day. However, for SETs 2 and 3, the feed contained 17α-methyl testosterone at 60mg/kg of feed. The second part of the experiment involved growth performance testing of fry in each SET. The growth experiment was conducted in rearing hapas that were inserted in a common pond for a period of 70 days. The body weight data were collected every 14 days (Tables 1 to 4). On the 70th day, the proportions of males and females in the four SETs was determined using Aceto-carmine staining method (Table 5). The pictures of the stained male and female gonads under compound microscope are presented in the published journal article at https://doi.org/10.1016/j.aqrep.2020.100274. Dataset presented in this paper is for body weights of fish from day 0 to day 70 and proportion of males and females in each SET on the 70th day of the experiment (Tables 1, 2, 3, 4 and 5). The data were analyzed using SPSS version 20.0. Chi-square goodness of fit test was used to investigate if the observed sex ratios significantly deviated from the expected sex ratios at 5% level of significance. The differences among fish body weights were determined using Analysis of Variance and significantly different means were separated using Duncan's multiple range test at the 5% test level of significance. These data are useful for various stakeholders that are interested in sexing juvenile tilapia and for scientists that conduct tilapia sex reversal experiments. This data can also guide hatchery managers during commercial production of all male tilapias which grow faster than those in the mixed sex tilapia culture.

Fish farming in Tanzania: the availability and nutritive value of local feed ingredients

ABSTRACT An investigative field survey was performed to gather baseline data on locally available feed ingredients and fish farming practices in different regions of Tanzania. More than 80% of respondents relied on locally available feed ingredients as a major feed supplement for their cultured fish, with maize bran being the most commonly used feed ingredient in all regions. Crude protein content in most analyzed local feed ingredients was medium-high, while crude fat content was high in some animal and agricultural by-products, and medium-low in other ingredients. Most respondents were males and the majority of fish farms were owned by individuals. Earthen pond was the most common fish farming system in all regions except Dar es Salaam. Semi-intensively mixed-sex tilapia monoculture was the dominating fish farming practice. The results of the survey presented provide a good platform for future development of culture systems and feeding strategies for tilapia in Tanzania.

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.

Characterization of the Production and Dissemination Systems of Nile Tilapia in Some Coastal Communities in Ghana

Aquaculture development has been identified as a key process to meeting the demand for cheap and readily available source of protein. The resultant has been the springing up of cages along the Volta Lake with most farmers producing Nile tilapia. However, the sector faces an array of challenges which needs urgent attention. A study was undertaken to ascertain the production systems and dissemination channel of Nile tilapia among farmers along selected coastal regions in Ghana. A survey of 190 farmers representing the fish farming community in the area was used -these comprised 187 males and 3 females. Pond culture and cage culture were the most common holding facilities used constituting 58.8% and 28.9% respectively. The production of all-male tilapia was popular among farmers and constituted 66.8% of production, while the production of mixed sex tilapia formed 25.8 %. The study revealed that the high prices of fish feed and lack of access to finance were the top ranking financial challenge facing fish farmers in the area corresponding to 73.2% and 51.1% of the response respectively. Other factors such as distance to hatchery and price of fingerling was a significant factor affecting the choice of source of fingerling for stocking (P&lt;0.05) for farmers who used dugout ponds. There was no clearly laid down protocol for dissemination the tilapia. Farmers (16%) who undertook dissemination directly supplied fingerlings and broodstock to other farmers. Investment of capital into tilapia production can improve productivity and profitability.

Growth Performance and Nutrient Utilization of Hormonal Sex-reversed Male and Mixed Sex &lt;i&gt;Oreochromis niloticus&lt;/i&gt; under Outdoor Rearing Condition

This study investigates the performance of all male and mixed sex tilapia ( Oreochromis niloticus ) raised in outdoor rearing conditions. All male tilapia were obtained by hormonal administration of 17 α-methyltestosterone (30 µg) into the diet of hatchlings of O. niloticus and fed them for 28 days. Both sex-reversed male and mixed sex O. niloticus were fed with coppens ® commercial diet and replicated thrice at 45% crude protein for 24 weeks Biological evaluation such as Mean Weight Gain (MWG), Specific Growth Rate (SGR) and Feed Conversion Ratio (FCR) were determined. Temperature, pH, conductivity and total dissolved solids were measured using standard methods. Data were analyzed using descriptive statistics and ANOVA at P=0.05. Result revealed that all male tilapia had significant weight gain (p<0.05) (5.93 ± 0.13 g) compared to the mixed sexes (2.19 ± 0.09 g). However, breeding activity was not noticed within the mixed sex tilapia population after a culture period of six months. Hence, poor performance could not be directly linked to spawning activity. The value of temperature, pH, conductivity and total dissolved solids were closely related and were within recommended range for the culture of tropical fishes. It was therefore hypothesized that 17 α-methyltestosterone besides achieving masculation, may have growth promoting characteristic. The detail mechanism responsible for this better performance could be the focus of future research.

Farming of Nile tilapia (Oreochromis niloticus) in backyard ponds in Sri Lanka: Culture practices, fish production and profitability

Government of Sri Lanka through Ministry of Economic Development implemented an island-wide multi-sector programme during 2011-2014 involving rural households with the objective of enhancing nutrition and also to provide supplementary income and livelihoods. Fish farming in backyard/home garden ponds was one of the components under this programme. This was the second attempt by the government to introduce small- scale pond fish farming in Sri Lanka, and the first attempt made during 1980-1983 was a failure.A total of 2,109 ponds covering an area of 105.45 ha have been established under the current programme. Information pertaining to culture practices, fish production, financial returns and costs involved in respect of these ponds were collected through administering a questionnaire. The survey covered fish ponds in the districts of Gampaha, Puttalam and Ampara. Nile Tilapia (Oreochrimis niloticus) was the only species used for farming. All-male or mixed sex tilapia are being farmed in these ponds. Considerable variations in stocking densities adapted, inputs, fish production, selling prices of fish, operational costs and profitability was observed among ponds in these districts. Average fish production per culture cycle were 9,192 kg/ha (Gampaha), 6,074 kg/ha (Puttalam) and 3,270 kg/ha (Ampara). Tilapia farming in ponds is profitable in all three districts. Profit margins are very attractive in respect of ponds in Gampaha and Puttalam.Recommendations to ensure sustainability in tilapia farming in ponds and for further expansion of fish farming in ponds with special reference to culture practices, fish production, inputs and role of government are made.

OVER-WINTERING GROWTH PERFORMANCE OF MIXED-SEX AND MONO-SEX NILE TILAPIA Oreochromis niloticus IN THE NORTHEASTERN BANGLADESH

The study was conducted to assess the over-wintering growth performance of mixed-sex and mono-sex male tilapia, Oreochromis niloticus. The experiment was carried out with two treatments each with three replicates for a period of 6 months from October 2012 to March 2013 in the Field Laboratory Complex, Bangladesh Agricultural University. In the first treatment (T 1 ), mixed-sex tilapia was stocked in 3 ponds with a mean initial weight of 4.80±0.18 g. In the second treatment (T 2 ), mono-sex male tilapia was stocked in another 3 ponds with a mean initial weight of 4.81±0.20 g. Fish were fed at the rate of 6% of fish body weight at the beginning of the experiments, then the feeding rates were gradually reduced to 2% for the third month and finally increased to 3% for the rest of the period. Water parameters in terms of temperature, dissolved oxygen, pH, transparency, alkalinity, ammonia and nitrite were within the range of fish farming. After 6 months of culture period, mono-sex male tilapia attained a significantly (P 0.05) difference of food conversion ratio and survival rate (%) values between the treatments. The benefit-cost ratio was calculated as 1.17 and 1.43 for mixed-sex and mono-sex male tilapia, respectively. The results suggested that it is possible to successfully culture tilapia during the winter period in Bangladesh, and the culture of mono-sex tilapia is more profitable due to its higher growth rate.

Polyculture of mixed-sex and male populations of Nile tilapia (Oreochromis niloticus) with the Mayan cichlid (Cichlasoma urophthalmus)

The purpose of this study was to test polyculture of Nile tilapia and the native Mayan cichlid, as an alternative production method of tilapia. The experiment had a 2×4 factorial design: the first factor was the population of tilapia (mixed-sex and 95% males) and the second factor was the proportion of Nile tilapia: Mayan cichlid (3:1, 5:1, 7:1 and 1:0). Proportion of 1:0 was tilapia monoculture. At stocking, tilapias were 11weeks old and weighed 24.0g and Mayan cichlids weighed 5.0g. Recirculating water systems were used, with 24 fiberglass tanks 1m3 with permanent water flow (7Lmin−1) and aeration. Each treatment had 3 replicates distributed randomly, and 24 fish were introduced in each tank (30fishm−3). The experiment lasted 21weeks, until tilapia reached marketable size. Fish were fed with extruded formulated diets for tilapia (40% and 30% crude protein). Daily feeding rate was restricted to between 4% and 1.8% of the fish biomass. Temperature, DO and pH (28.0±1.1°C, 5.2±1.2mgL−1 and 7.9±0.2) were within the appropriate ranges for growth, and TAN, nitrites and total alkalinity (0.29±0.22mgL−1, 0.04±0.03mgL−1 and 238±27mgL−1) were within safe ranges. Average survival was high (99%) and no differences were found between populations and among proportions. Nile tilapia Stirling strain showed early (45g after 3 experimental weeks) sexual maturation and growth dimorphism. Significantly better total yield, FCR and final tilapia body weight were obtained in the 95% male population (9.26kgm−3, 1.39 and 383g) than in the mixed-sex population (7.70kgm−3, 1.52 and 315g). The presence of the Mayan cichlid did not affect tilapia performance. The final weight of Mayan cichlid was significantly higher in the mixed-sex tilapia population (45.9g) than in the 95% male population (34.4g). Mayan cichlid growth was inversely proportional to its density, with final weights of 45.5g, 39.0g and 34.3g (7:1>5:1>3:1). The differences in Mayan cichlid growth are associated with intraspecific competition for available tilapia larvae. Mouth brooding tilapia females with eggs or larvae were observed in both tilapia populations and in all proportions. When fish were weighed some tilapia females released their larvae in the tanks, and both Mayan cichlid and tilapia males were observed preying on them.

Effect of repeated partial cropping on population dynamics and yield of Oreochromis niloticus (L.) during polyculture with Heterobranchus longifilis (Val.)

The effect of repeated cropping of half the number of young and large adults on productivity and dynamics of Oreochromis niloticus was investigated during polyculture with Heterobranchus longifilis. Mixed-sex, large-sized and young adult tilapia of 841±0.3 g and 841±0.23 g were cultured with 40 catfish fingerlings in triplicate 36 m2 earthen ponds in 1 and 2 treatments respectively. At the 4th, 6th, 12th, 26th and 32nd week, cropping was done in treatment 2 and the weights of the crop were used to enrich supplementary feed, by displacing an equal weight of ingredients in treatment 1. Realized supplementary feed crude protein level was 12.9 and 18.3±5% in treatments 1 and 2 respectively. Feeding was at 1% body weight thrice daily. Weight data were analyzed with ANOVA and t-test. Surplus production of O. niloticus from treatment 2, calculated as sum of periodic harvest + final harvest minus final harvest in treatment 1, was 249±25 g per week. Treatment 2 had significantly higher H. longifilis harvest mean weight and growth rate (percentage per day) (p<0.01), with densities (p<0.05). It also has higher numbers of zooplankton and phytoplankton species, cyanophyceae and diatoms, as well as O. niloticus size susceptible to catfish predation. Chlorophyceae dominated the phytoplankton in both treatments. The implication of tilapia surplus production for catfish-tilapia polyculture is thus discussed. Key words: Oreochromis niloticus, partial harvest, population dynamics, compensatory growth, standing crop, surplus production, food availability, earthen pond.

Increased androgen receptor expression in muscle tissue contributing to growth increase in androgen-treated Nile tilapia

The aim of this study was to investigate the molecular mechanism behind androgen-induced sex reversal and growth increase in Nile tilapia. Three-day-old mixed-sex tilapia juveniles were treated with differential dose (0, 5, 10, 20, 30 mg/kg diet) and duration (0, 15, 30, 45, 60 days) regimes of 17α-methyltestosterone. Treatment regimes 10, 20, 30 mg/kg-30, 45, 60 days showed ~95% males, while 0 mg/kg-0 days (control) showed ~50% males (P < 0.01). Next, tilapia was cultured for 6 months in cistern and pond culture systems with 17α-methyltestosterone-treated diet (10 mg/kg) for three different durations: 0 days (control), 30 days (30-day-treated), and 180 days (throughout-treated). Fish in pond culture showed significantly higher (P < 0.05) final weight compared with tilapia in cistern culture (235.76, 156.82 g, respectively). Both 30-day-treated and throughout-treated fish showed significantly higher (P < 0.05) final weight, length, daily weight gain, specific growth rate, and muscle protein content compared with control fish. The androgen receptor β mRNA and protein expression levels in both 30-day-treated and throughout-treated fish were significantly higher (~twofolds, P < 0.05) compared with hormone-untreated control males. However, there was not much difference for all these parameters among the two hormone-treated groups. This higher growth probably results from an androgen-induced increased ‘androgen-androgen receptor’ mediated anabolic pathway. Serum testosterone concentration of 30-day-treated fish after 6 months was similar to that of control males (0.9 ng/ml). Moreover, culture of 17α-methyltestosterone-treated monosex tilapia was found beneficial than hormone-untreated mixed-sex tilapia culture for maintenance of natural fish diversity in indigenous water bodies.

Growth of Mixed-Sex and Monosex Nile Tilapia in Different Culture Systems

Growth of 17α-methyltestosterone treated monosex Nile tilapia, Oreochromis niloticus was compared with hormone untreated mixed-sex fish in four different culture systems. The experiment had 2 X 4 factorial design: the first factor was presence or absence of hormone treatment (monosex and mixed-sex fish), the second factor was related to culture system (cistern, flow-through, pen and pond). Fish were cultured under similar feeding regime and stocking density for six months and different growth parameters such as body weight, length, daily weight gain (DWG), specific growth rate (SGR), proximate body composition and survival rate were analyzed. Monosex tilapia showed significantly higher (P-value 0.05) among mixed-sex and monosex fish and between different culture systems. Monosex tilapia in pond culture system showed the highest weight, DWG and protein content while mixed-sex tilapia in cistern culture system showed the lowest weight, DWG and protein content. Considering the results of this study, culture of monosex tilapia in earthen ponds might be considered the ideal method for tilapia culture in India.

Impacts of Aquaculture Development Projects in Western Cameroon

To measure the impact of past projects on the sustained adoption and development of aquaculture, and to assess the potential for future growth, a participatory rural appraisal (PRA) based on the Research Tool for Natural Resource Management, Monitoring and Evaluation (RESTORE) of 100 farmers (62 with fishponds, 38 without) was undertaken between January and August 2001 in the Noun Division of Western Province, Cameroon. The average household of 14 persons possessed 5.5 ha of land. Educational level is low (less then 35% above primary, 24% illiterate). Most fish producers were small-scale farmers (79%). Of the 360 fish farmers possessing 445 fish ponds (250 m2 average surface area), only 23% were active. Production is primarily based on earthen ponds stocked with mixed-sex tilapia (Oreochromis niloticus) grown alone (42%) or in polyculture (54%) with the African catfish (Clarias gariepinus). Most ponds are poorly managed, containing underfed fish despite the availability of large quantities of agricultural by-products that could be used as pond inputs. Average annual yield is 1,263 kg/ha. Despite a number of aquaculture development projects over 30 years, there were no significant differences (P < 0.05) in household economics and farming systems between fish farming and non-fish farming families. According to active fish farmers, the major constraints to increasing aquaculture production to make it economically interesting are: lack of technical assistance (46%) and lack of good fingerlings (30%). Recent political and economic changes have altered the outlook for aquaculture in Cameroon, and a development strategy based on new rural development policies is discussed.

Comparative Growth Performance of Mixed-Sex and Monosex Nile Tilapia Population in Freshwater Cage Culture System under Indian Perspective

Cage culture is one of the important methods for intensive culture of tilapia in large water impoundments. But,information related to growth performance of androgen-treated monosex tilapia population during cage culture underthe ecological conditions of India is limited. The aim of this study was to compare the growth potential of control,mixed-sex and androgen-treated, monosex tilapia in confined environment of cages. Control and hormone treated fishwere stocked separately in mesh cages at a density of 50 fry / m3 and it was found that the androgen treated monosexfish grew significantly larger than their control mixed-sex counterparts. The monosex population showed a significantlyhigher weight, length, depth, specific growth rate, daily weight gain, protein efficiency ratio and body protein contentthan the mixed-sex tilapia population. Thus, culture of hormone treated monosex tilapia in cages can be consideredideal for augmented production of the fish under Indian context.

PERFORMANCES OF POPULATIONS OF SEX REVERSED TILAPIA AND GENETICALLY MALE TILAPIA IN FINGERLING PONDS

One of the most popular techniques in mass production of all or nearly all male tilapia population is through sex reversal. However, cross mating of YY super male with regular brood-stock is gaining popularity and has been practiced by aqua-culturists. This study was conducted to evaluate the performance of 2 populations of sex reversed tilapia (sex reversed with dietary application of 17-α methyl testosterone, SRT-1, and sex reversed with dietary administration of imidazole, SRT-2) and 1 population of genetically male tilapia (GMT) derived from YY super male until the end of fingerling rearing period. Mixed sex tilapia (MST) derived from normal mating was used as the control population. The results showed that the daily growth rates of SRT-1, SRT-2, GMT, and MST were 0.12, 0.11, 0.20, and 0.07 g/day, with survival rates were 57.83%, 64.67%, 39.67%, and 68.78%, respectively. The GMT has higher harvest yield than the other populations; SRT-1 (+15.73%), SRT-2 (+6.37%), and MST (+20.82%).