Tilapia Hatcheries Research Articles

Two-year surveillance of tilapia lake virus (TiLV) reveals its wide circulation in tilapia farms and hatcheries from multiple districts of Bangladesh.

Tilapia lake virus (TiLV) is an emerging pathogen in aquaculture, reportedly affecting farmed tilapia in 16 countries across multiple continents. Following an early warning in 2017 that TiLV might be widespread, we executed a surveillance programme on tilapia grow-out farms and hatcheries from 10 districts of Bangladesh in 2017 and 2019. Among farms experiencing unusual mortality, eight out of 11 farms tested positive for TiLV in 2017, and two out of seven tested positive in 2019. Investigation of asymptomatic broodstock collected from 16 tilapia hatcheries revealed that six hatcheries tested positive for TiLV. Representative samples subjected to histopathology confirmed pathognomonic lesions of syncytial hepatitis. We recovered three complete genomes of TiLV from infected fish, one from 2017 and two from 2019. Phylogenetic analyses based on both the concatenated coding sequences of 10 segments and only segment 1 consistently revealed that Bangladeshi TiLV isolates formed a unique cluster within Thai clade, suggesting a close genetic relation. In summary, this study revealed the circulation of TiLV in 10 farms and six hatcheries located in eight districts of Bangladesh. We recommend continuing TiLV-targeted surveillance efforts to identify contaminated sources to minimize the countrywide spread and severity of TiLV infection.

Innovative Technologies to Promote Sustainable Recirculating Aquaculture in Eastern Africa—A Case Study of a Nile Tilapia (Oreochromis niloticus) Hatchery in Kisumu, Kenya

Lake Victoria, regionally important both as a source of food and income, is under pressure due to overfishing and severe pollution. Currently, the vast majority of east African aquaculture is open-pond based. The adoption of modern and sustainable aquaculture technologies and practices-in this case study recirculating aquaculture systems (RAS)-will help the region increase food security and decrease its current reliance on imported fish and stressed wild stock. To this end, VicInAqua, a project under the EU Horizon 2020 program, has developed a pilot Nile Tilapia (Oreochromis niloticus) hatchery in Kisumu, Kenya using RAS adapted to local conditions. The hatchery is designed as a flexible, scalable, and modular system. An online monitoring system enables farmers to access farm data from both fish tanks and the supporting renewable energy systems, allowing around-the-clock monitoring and control. The hatchery is linked to a 14.3 kWp Photovoltaic (PV) system, including a 30 kWh Li-battery storage, to supply sustainable electricity. The water for the RAS, treated by a membrane bioreactor (MBR) and certified for use in aquaculture and agriculture, comes chiefly from Kisumu's municipal sewage, which reduces the farms' reliance on an expensive and occasionally intermittent potable water supply. Combining these technologies represents an industry first and offers a working example for larger-scale future developments. The purpose of the project is to demonstrate the possible technologies and practices in situ as well as provide a template for future development and investment. The hatchery is used by the Department of Livestock, Agriculture and Fisheries, Kisumu County, Kenya, as a training and demonstration facility to promote the aquaculture sector and increase the awareness, knowledge, and skills of fish farmers, as well as provide high quality fingerlings to cage farmers within the lake. Integr Environ Assess Manag 2020;16:934-941. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Trichodinids and monogeneans infestation among Nile tilapia hatcheries in Egypt: prevalence, therapeutic and prophylactic treatments

The current study aimed to investigate the most prevalent ectoparasites among some Egyptian tilapia hatcheries and find out the appropriate therapeutic and prophylactic doses. For that, 500 Nile tilapia fry weighing 0.02 g were collected from several hatcheries at Sharkia Governorate, Egypt, over the period of April to September 2017, examined for the presence of trichodinids and monogeneans. The prevalence and intensity of such parasites were recorded. LC50 of the five selected chemicals was examined against 1000 healthy fry for 24 h. The therapeutic and prophylactic doses were evaluated against 360 heavily infested fry and 600 newly hatched ones for 72 h and 3 weeks of indefinite treatment, respectively. Infested fish exhibited erratic swimming, detached skins, and hemorrhagic gills. The most common parasites identified were Trichodina fultoni, T. salmincola, Cichlidogyrus sp., and Cichlidogyrus tubicirrus. The LC50 was 81.31, 235.57, 7.19, and 15.48 ppm for formalin, hydrogen peroxide, potassium permanganate, and methylene blue, respectively. All chemicals were effective in treating trichodinids, while formalin was the only efficient chemical to treat monogeneans 72 h post-exposure. Potassium permanganate showed the best preventive activity against both types of parasites for successive 1 week post-exposure. This study highlighted the optimal use of chemical drugs for the control of ectoparasites from an economic perspective.

Nitrogen and Phosphorus budget for Nile tilapia hatchery

Tilapia hatcheries if not well managed, it can cause environmental damage. The present study was designed to quantify the impacts generated by Nile tilapia hatcheries, through applying environmental indicators, which is necessary for tilapia hatcheries sustainable development. Three culture trials, each of 15 days, have been carried out to determine environmental indicators: the nitrogen and phosphorus flux and nutrient mass balance based on inputs from feed and losses in fish harvest, nutrients load in the effluent water, and fish bio-solid wastes (sludge). In each, three cement ponds were assigned to determine the nutrients input and loss for 15 days intervals, fry production cycle. The results showed that every 1 Kg feed of 35% protein produce 420 g sludge, of which 262 gm fish excretion. Uneaten feed was found to represent 15.8-20% of the introduced feed and produce 37.6 - 43.2 % of sludge. Fish retained at least 25.8 ± 3.91 % and 2.74 ± 0.37 % of the input feed nitrogen and phosphorus, respectively. While the sludge contained 11.3 ± 0.78 % and 32.62 ± 14.46 of the feed nitrogen and phosphorus, respectively. Effluent water contained 43.64 ± 6.45 % and 50.22 ± 16.63 % of feed nitrogen and phosphorus, respectively, distributed in three main fractions: particulate form; dissolved organic and dissolved inorganic forms. The feed nitrogen recovery in the present study was 80. 57%, while the phosphorus recovery reached 85.58% of the feed phosphorus content. Fry production is discussed in response to the feed protein content and feeding rate.

Evaluating the influence of different water sources on water quality, survival and growth rates of Nile tilapia (Oreochomis niloticus) larvae in tilapia hatcheries

This study was conducted to evaluate the effect of different water sources on survival rate and growth performance of Nile tilapia (O. niloticus) larvae during nursing period. Larvae (post yolk sac stage) were stocked at 50000 / pond and fed 48 % crude protein diet 6 times daily at rates of 35, 26 and 18% of their weight in the successive three weeks, respectively. Nine concrete ponds assigned for 3 treatments, triplicates in each. The ground water and agricultural drainage water were the water sources in the first and third treatments, respectively, while the second treatment received a 1: 1 mixture of the two water sources. Water samples, for some physico-chemical analysis, were monitored before pumping water into the ponds and within the ponds at each fry harvest. The experiment lasted for 21 days and replicated four times. At the end of each rearing period, fry number was estimated in each pond; the survival and growth rates were calculated. The results showed that the significantly highest survival and growth rates were obtained in the mixed water treatment. Mixing agricultural drainage water with ground water results the most suitable water quality for Nile tilapia performance than each of these sources separately. Generally, water quality parameters for the studied sources at the end of each rearing period were within the acceptable range for fish culture.

The larasati tilapia (Oreochromis niloticus) fingerling rearing activity in PBIATJanti, Klaten, Central Java: its performance through survival rate

Tilapia (Oreochromis niloticus) is one of the fisheries commodities that are popular with many people. In aquaculture, fingerling is the main component that support the business. This study aimed to provide information on the performance of the rearing techniques of tilapia fingerling so that the information could be used in tilapia hatchery activities. This study was conducted at Loka PBIAT Janti, Klaten, Central Java on December 2018-January 2019. The work method used in this research was descriptive method with supported by primer and ssecondary data, especially survival rate data. With high quality rearing techniques, the survival rate of larasati tilapia fingerling in PBIAT Janti showed high level of 88.81%.

Nile tilapia (Oreochromis niloticus) fish hatchery technique: the survival rate evaluation in IBAT Pandaan, Pasuruan, East Java

Nile tilapia (Oreochromis niloticus) is a freshwater fish that has great potential to be developed and has a fairly high economic value. One of the important factors to support the success of Tilapia fish farming is the availability of seeds. Instalasi Budidaya Air Tawar (IBAT) Pandaan is contributing to the fulfillment of the superior seeds through the activities of tilapia fish hatchery. The purpose of this study was to identified the performance of hatcheries techniques of tilapia fish in Instalasi Budidaya Air Tawar (IBAT) Pandaan, Pasuruan, East Java through the survival rate. This research used in this study was descriptive method, supported by primer and secondary data. The survival rate result showed that high value of survivaval rate of 92% and showed good condition of fish This was due to the good technique of tilapia hatcheries included the pond preparation, broodstock selection and preparation, hatchery, feeding, and water quality control.

Characterizing the genetic structure of introduced Nile tilapia (Oreochromis niloticus) strains in Tanzania using double digest RAD sequencing

Tilapia hatcheries in Tanzania rely heavily on importing germplasm. Nevertheless, the genetic structure of the imported stocks is poorly understood. In the current study, the level of genetic diversity and differentiation of eight populations of Nile tilapia (Oreochromis niloticus) strains imported in Tanzania was investigated. Four of the studied strains originated from Thailand, three from Uganda, and one from the Netherlands. Double-digest restriction site–associated DNA sequencing (ddRAD-seq) was applied to identify and genotype single nucleotide polymorphisms (SNPs). In total, 2214 SNPs passed all the quality control steps and were utilized for downstream analysis. Mean heterozygosity estimates were higher for the Thailand strains (Ho, 0.23) compared with the strains from Uganda (Ho, 0.12). Low genetic distance was observed amongst populations from the same geographic origin (Fst, 0.01–0.04). However, genetic distance between populations from different geographic origins was substantial (Fst, 0.24–0.44). Bayesian model–based clustering (STRUCTURE) and discriminant analysis of principal components (DAPC) grouped the studied animals into three distinct clusters. A cross-validation approach (where 25% of animals from each population were considered of unknown origin) was conducted in order to test the efficiency of the SNP dataset for identifying the population of origin. The cross-validation procedure was repeated 10 times resulting in approximately 97% of the tested animals being allocated to the correct geographic population of origin. The breeding history and hatchery practices used to manage these stocks prior and after import appear to be the main factors for the genetic diversity observed in this study. Our study will help inform hatchery stock management and future breeding program designs in Tanzania.

Strategi Pengembangan Usaha Pembenihan Ikan Nila di Balai Benih Ikan (BBI) Lokal Gunung Manau Kecamatan Batuman di Kabupaten Balangan

The research aims to identify internal and external factors, formulate alternative strategies, and prioritize strategies in developing the tilapia hatchery business at the Gunung Manau Local Fish Breeding Center, Batumandi District, Balangan Regency. The basic method used is descriptive method and carried out by survey techniques. The data used in this study are primary and secondary data. Data analysis methods used (1) SWOT Analysis, (2) IE and SWOT matrix (3) QSP matrix. The results of the study reveal that (1) the main underlying strength is easily accessible production facilities, (2) the main disadvantage is that marketing outside the region is still lacking. (3) The main opportunity to get assistance from the government. (4) Whereas the fundamental threat is the effect of the dry season. (5) Based on the IE matrix, the strategy is market penetration and product development. (6) The results of the SWOT matrix from the alternative strategies implemented are maintaining seed quality and increasing production through increased application of Standard Operating Procedures (SOP), Utilization of feed probiotic processing technology and feed training and increasing the number, improving the performance of technical officers in managing business seeding by providing encouragement, monitoring and evaluation as well as cooperative relations of the related institutions. (7) The priority strategy that can be applied is to improve the performance of technical officers

Transmission of Francisella noatuensis subsp. orientalis from subclinically infected hybrid red tilapia broodstock (Oreochromis sp.) to their offspring

Francisella noatunensis subsp. orientalis (Fno) has been reported as an important bacterial pathogen causing significant mortality (30–95%) in farmed tilapia in broad geographic areas. However, we found that there was a proportion of broodfish in our laboratory that appeared to be healthy but which tested positive for Fno. We therefore hypothesized that Fno might be able to be transmitted from subclinically infected tilapia mouthbrooders to their offspring through the current practice of fry production in tilapia hatcheries. To prove this, experimentally infected hybrid red tilapia broodstock were mated and their offspring were examined for the presence of Fno. In this study, three pairs of infected broodfish were mated for natural spawning and fertilized eggs from each couple were then collected from the female mouths for artificial incubation. The newly hatched larvae were cultured for 30 days and sample collection was performed at different developmental stages i.e. yolk-sac larvae, 5 and 30-day old fry. The results showed that the ovary and testis of all 3 pairs of the broodstock, as well as their fertilized eggs and offspring were Fno positive by Fno-specific PCR and in situ DNA hybridization. In summary, this study revealed that with the current practice in tilapia hatcheries, Fno might be able to transmit from subclinically infected tilapia mouthbrooders to their offspring. Therefore, using Fno-free broodfish in tilapia hatcheries should be considered in order to produce Fno-free tilapia fry.

Assessment of the impact of dissemination of genetically improved Abbassa Nile tilapia strain (GIANT‐G9) versus commercial strains in some Egyptian governorates

WorldFish initiated a selective breeding program in Abbassa—Egypt to develop and produce the genetically improved Nile tilapia strain known as “Genetically Improved Abbassa Nile tilapia (GIANT)”, adopting the same technology used for the Genetically Improved Farmed Tilapia (GIFT), in Asia. WorldFish provided the Ninth Generation (G9) broodstock of the GIANT to 11 Broodstock Multiplication Centers (BMC’s) in five governorates; these centres then disseminated improved mixed‐sex fry to 160 tilapia hatcheries which supplied all‐male fry to 1,500 fish farms in 2017. We present results of an impact assessment of the G9 of GIANT in 83 of these fish farms in four Egyptian governorates (Kafr El‐Sheikh, Fayoum, Behera and Alexandria). Results indicate that the use of GIANT in all governorates achieved significantly higher (18.8%) fish yields (12.3%–26.4%) and 15.7% lower FCR (feed conversion ratio), reflecting a positive impact on their net profits compared with those who used commercial strains. Overall, fish farmers who stocked GIANT had significantly higher average fish sales (5,567 US$/ha) than those who stocked non‐improved commercial strains (5,192 US$/ha) in all governorates. However, when comparing within governorates, the difference was significant only in Fayoum and Alexandria noting a mixed performance of the GIANT strain. The mixed performance indicates that some hatcheries may have crossed the different strains, which lowered the performance differences. To get an objective analysis of the performance of the GIANT, it is recommended that similar assessment be undertaken with new generations of the strain supported by on‐farm performance trials.

Evidence of potential vertical transmission of tilapia lake virus.

Tilapia lake virus disease (TiLVD) is an emerging viral disease in tilapia with worldwide distribution. Although the horizontal transmission of TiLV has been demonstrated through the cohabitation of infected fish with susceptible fish, no direct experiment showed the potential of vertical transmission from broodstock to progeny. In this study, natural outbreaks of TiLV in broodstock and fry in two tilapia hatcheries were confirmed. The TiLV genomic RNA was detected in liver and reproductive organs of infected broodstock, while infective virus was isolated in susceptible cell line. In situ hybridization assay confirmed the presence of TiLV in the ovary and testis of naturally infected fish and experimentally challenged fish. Moreover, early detection of TiLV in 2-day-old fry and the presence of TiLV genomic RNA and viable virus in the testis and ovary suggested the possible transfer of this virus from infected broodstock to progenies. As infective virus was present in gonads and fry in natural outbreak and experimental fish, the importance of biosecurity and prevention of the virus to establish in the hatchery should be emphasized. Hence, the development of TiLV-free broodstock and the maintenance of high biosecurity standards in the hatcheries are essential for any attempt of virus eradication.

Can larval growth be manipulated by artificial light regimes in Nile tilapia (Oreochromis niloticus)?

Photoperiod and light intensity have been shown to play important roles in the growth of larval fish. In terms of the effect of light conditions on the larval growth of Nile tilapia, previous studies are confined to examining the effect of only photoperiod rather than of their combined effects. The face-centered composite experimental design and response surface methodology were utilized to investigate the combined influences of photoperiod and light intensity on the feed conversion and larval growth of Nile tilapia in this study. Based on the results of pilot experiments, photoperiod ranged from 8 h to 24 h, light intensity from 100 lx to 2000 lx (1.26–25.20 μmol m−2 s−1). Results showed that under indoor recirculating rearing system varying growth rhythms occurred with different light conditions; interaction between the two factors was detected, and the light intensity was more important in impacting on growth than photoperiod in the larval stage, implying that light intensity and photoperiod ought to be examined in concert rather than separately. If light intensities are held invariable, the photoperiod studies would lead to the choice of >18 h photoperiod for the best larval growth. Response surface of the larval growth was roughly consistent with that of feed conversion, indicating that the larval growth was realized through feed conversion. Relationship of the larval growth and feed conversion to artificial light conditions could be reliably quantified in a second-order form, through optimization of which optimal two-factor combination, 14–16 h/1650–1900 lx (20.79–23.94 μmol m−2 s−1), was derived with the reliability as high as ca. 98%. There is therefore the potential for maximizing larval growth in hatcheries via manipulation of artificial light regimes. According to our findings, continuous lighting should not be recommended for optimal growth in larviculture. These findings underscore the important role of light conditions during the larval stage of Nile tilapia and should be taken into consideration for the optimization of rearing protocols in Nile tilapia hatcheries.

Effects of aflatoxin B1 on reproductive performance of farmed Nile tilapia

ABSTRACTThis study evaluated the effect of dietary aflatoxin B1 (AFB1) on growth, milt and egg quality in matured Nile tilapia (Oreochromis niloticus). Triplicate groups of Nile tilapia (initial body weight 24.1 ± 2.6 g) were fed with either of four diets (Diets 1 to 4) designed to contain 0, 20, 200 and 2000 μg AFB1 kg−1 diets for 24 weeks. After 24 weeks of AFB1 exposure, growth was significantly (P <0.05) different between the control and the AFB1 exposed treatments in both sexes. No significant differences were observed in 17β-oestradiol, absolute fecundity, oocytes volume and diameters between AFB1 exposure groups and the control group. However, we observed a significant reduction in relative fecundity and gonad somatic index (GSI) in females fed 2000 μg AFB1 kg−1 diet. On the other hand, we observed significant differences (P <0.05) in gonadosomatic index (GSI), testosterone, milt count and motility between males in the control group and AFB1 treatments. We conclude that rearing Nile tilapia with aflatoxin-contaminated diets for a prolonged period affects milt quality, fecundity (at higher doses) and growth performance. This implies that for optimal seed production, provision of aflatoxin free diets should be part of the management practices in Nile tilapia hatcheries.

Application of multiplex quantitative polymerase chain reaction methods to detect common bacterial fish pathogens in Nile tilapia, Oreochromis niloticus, hatcheries in Costa Rica

Edwardsiella spp., Streptococcus spp., and Francisella noatunensis subsp. orientalis are some of the most important fish pathogens affecting global tilapia, Oreochromis spp., aquaculture. In Costa Rica, the aquaculture industry is dominated by freshwater‐cultured Nile tilapia, Oreochromis niloticus, which are raised in all seven national provinces. At present, little is known regarding the diversity of pathogens present in these facilities, and definitive identification of agents associated with disease outbreaks are rare. To evaluate the prevalence of common bacterial pathogens in these systems, this study used multiplex quantitative polymerase chain reaction (qPCR) assays targeting Edwardsiella, Streptococcus, and Francisella species as a diagnostic and surveillance tool. In 2017, seven different tilapia hatcheries were visited, and 350 fingerlings were subjected to necropsy and molecular diagnostic evaluation. Fish exhibiting gross signs of disease were subjected to histological and microbiological analysis. For the first time, Edwardsiella anguillarum was recovered and molecularly confirmed from diseased tilapia in Costa Rica. In addition, F. noatunensis subsp. orientalis was identified in a region of Costa Rica where it had not been previously reported.

Some Spawning Performance Parameters of Cultured Nile Tilapia Oreochromis niloticus, under Brackish Water

Tilapia is one of the most important cultured fish in the world. However, the gap between seed supplies and farmers' demand is one of the serious limitations for tilapia culturists. Notice about different effective agents on tilapia reproduction might be useful for increasing of production and better management of tilapia hatcheries. In the present study, higher efficiency of tilapia Oreochromis niloticus hatchery was considered based on the impact of sex ratio, stocking density, photoperiod, water salinity and replacement period on spawning performance. Sex ratios 1:1, 1:4 and 1:7 (Male: Female), stocking densities 2, 3.5 and 5 fish/m3, photoperiods 6:18, 12:12 and 18:6 (Light:Dark), water salinities 12, 8, 4 and 0 ppt, also10 and 15 days replacement of breeders were studied. Fecundity,breeder and egg per day,spawning intervals, egg diameter and weight were investigated. Results showed stocking density 5 fish/m3, photoperiod 12:12, 8 ppt water salinity and 10 days replacement had better performance. Sex ratio treatments had similar performance.

The motility and motion duration of jatimbulan tilapia (Oreochromis niloticus) spermatozoa in different salinity

Tilapia hatchery is still conducted in freshwater and seeds are death simultaneousy when cultivated in high salinity due to the acclimatization process. An alternative method to implement hatchery at high salinity is required. This study aims to determine the salinity of activation medium that provides the best Jatimbulan Tilapia sperm motility and motion duration at high salinity. The study applies completely randomized design (CRD), which consists of 5 treatments (0 ppt, 4 ppt, 9 ppt, 14 ppt and 19 ppt) and 4 repetitions. The parameters consists of sperm motility, motion duration, fresh sperm data (volume, color, odor, pH, consistency, and the concentration of sperm) and sperm abnormalities. The results exhibited that salinity significantly (p < 0.05). Influeneed the sperm motility and motion duration. Motility reaches its best at 0 ppt and 4 ppt (93.4 % and 87.8 %). For motion duration, best condition was in 0 ppt and 4 ppt treatments, totaling 2128 seconds and 1961.5 seconds. Meanwhile, sperm did not move when treated in waters with 9 ppt, 14 ppt and 19 ppt salinities.

BUSINESS PROSPECT OF THE TILAPIA HATCHERIES BY STANDARD OPERATING PROCEDURE APPLICATION OF GOOD HATCHERY PRACTICES (GHP) IN BANJAR REGENCY SOUTH KALIMANTAN

This research aimed to (1) analyze the profit of the tilapia hatchery business in Banjar Regency with GHP application and comparing it with the profit before it applied GHP; and (2) to analyze the investment feasibility of the tilapia hatchery business with GHP application in Banjar Regency. This research was carried out in the Karang Intan District, Banjar Regency, South Kalimantan, with the community GHP certified hatchery units as the object. The collected data was the data that directly originated from observation results in the location of the research, and other supporting data, which related to the object of the research. The results of the research showed that by applying GHP, the tilapia hatchery business gave more profit than before applying it. By applying GHP, the tilapia hatchery business developed very profitably and feasible to be carried on. The result of investment feasibility analysis showed that the NPV was positive, the Net BCR was more than 1, the IRR was more than discounted rate, and the period of the return of investment was faster than the project period.

Genetic parameters for resistance against Flavobacterium columnare in Nile tilapia Oreochromis niloticus (Linnaeus, 1758).

Columnaris disease is a major cause of mortality in tilapia hatcheries and commonly occurs during the summer season in Thailand. One way of reducing the problem is by selective breeding for increased disease resistance. The objective of this study was to estimate quantitative genetic parameters for resistance against columnaris in the Chitralada 4 strain of Nile tilapia. Data from 43 full-sib families (2,580 records) of fry (age=32±4days post-hatch) were used in the analyses. Initially, fry were subjected to bath challenge with Flavobacterium columnare (LD50 concentration=1.2×106 CFU/ml) for 14 days. Disease resistance was defined as the number of days from challenge until death (DD) or as a binary trait (dead/alive) on day 14. Linear animal and sire-dam models were used for DD, while threshold animal, threshold sire-dam, binary linear animal and binary linear sire-dam models were used for binary outcomes. Covariate effect of age, fixed effect of challenge day and random effects of the individual animals or sires and dams were included in the models. Mean survival was 32.4±11.6%, and survival rates of the best and poorest families were 70% and 8%, respectively. The highest estimate of heritability (0.30±0.025) was obtained under the threshold sire-dam model. Heritability estimates for DD (0.16±0.034 and 0.17±0.046) were comparable to those obtained from the threshold animal (0.15±0.031) and the binary linear (0.14±0.045 and 0.15±0.044) models. The linear animal and sire-dam models for DD and the threshold sire-dam models performed equally with similar values of rEBV (0.629, 0.628 and 0.627) and accuracy of selection (0.793, 0.793 and 0.791). This study reveals the potential of selective breeding to increase disease resistance to F.columnare in the studied population of Nile tilapia.

Efficacy of some disinfection methods on the microbial load of eggs and equipment of tilapia hatchery

In fish hatcheries, high densities of eggs are maintained in incubators with microbial loads that vary from those in the natural habitat. Moreover, the accumulation of organic debris on tools used in the hatchery facility assists the spread of infectious diseases. This study was designed to evaluate the effect of different iodophor concentrations (10, 50, 100 and 150 ppm) for different contact times (5, 10 and 15 min) on total bacterial count (TBC) and total fungal count (TFC) and hence on the hatchability percentage of tilapia eggs. In addition, the effect of common salt (NaCl), sunlight exposure, 1% Halamid®, 1% Virkon S® and 3% Aquazix® for contact times (5, 10 and 15 min) in reducing TBC and TFC on hatchery equipment (buckets, nets and dishes)was also evaluated. Iodophor treatment at 10 ppm for 15 min resulted in significant reduction of both TBC and TFC on tilapia eggs by ≥ 4 log10 reductions but failed to achieve complete disinfection of egg surface. Conversely, 50 ppm or higher iodophor concentrations did not display antimicrobial activity after all tested contact times. Hatchability percentage was insignificantly different between 0 ppm (90%) and 10 ppm (94%) of iodophor. However, 10 ppm iodophor was significantly different (P < 0.05) from 50 ppm (85%) and 100 ppm (65%). At 150 ppm, there was no hatchability. After application of different disinfectants, limited to general bactericidal activity of ≥ 4 log10 reduction was observed in common salt (NaCl 150 g /7 liters) after 15 min in dishes only, sunlight exposure after 10 min in dishes onlyand 3% Aquazix after 15 min in all tools. Significant and 100% log reduction of both TBC and TFC was observed in 1% Halamid®after 10 min and 1% VirkonS®after 15 min.