Fish Diseases Lec 4 - Tilapia Culture PDF

# Fish diseases ## Lec 4 ### Tilapia Culture #### Dr. Aya Abdelkhalik الفرقة: 4 The Progress Group Application # Tilapia Culture The remarkable success of tilapias as a farmed fish can be attributed to: 1. Desirable flesh quality: Tilapias have white flesh, with neutral taste and firm texture....

# Fish diseases ## Lec 4 ### Tilapia Culture #### Dr. Aya Abdelkhalik الفرقة: 4 The Progress Group Application # Tilapia Culture The remarkable success of tilapias as a farmed fish can be attributed to: 1. Desirable flesh quality: Tilapias have white flesh, with neutral taste and firm texture. As a result, tilapias have gained acceptance in a wide variety of human cultures with differing tastes and food preferences. 2. Ease of farming: Tilapias are easy to hold and breed in captivity. 3. They tolerate crowding, relatively poor water quality and are relatively resistant to infectious diseases. 4. They can be grown in a wide variety of aquaculture systems. 5. They eat algae and detritus naturally produced in culture systems as well as manufactured feeds containing ingredients derived from plants. 6. They reach typical market size (500-800 g) in about 6-8 months under optimum water temperature (28-30 °C). ## Family, Species & Genetic Variation * Tilapias belong to the family of Cichlidae, a large family of tropical freshwater fish, which have bilaterally compressed body and exhibit parental care. * The common term 'tilapias' refers to pure species as well as hybrids belonging to the genera tilapia. * Sarotherodon and Oreochromis, especially the large species that are commercially exploited. * Tilapia can be classified according to breeding behavior into 2 groups: * Mouth brooder * Substrate spawner ## Mouth Brooder | Def | Description | | --- | --- | | Species of tilapia in which oral incubation of fertilized eggs take place until hatching | | a. Male prepare nest then attract the female | | b. female laying eggs | | c. male ← fertilization | external | | Genus oreochromis | female only responsible for oral incubation of fertilized egg | | Examples | | | 1. Oreochromis niloticus | | 2. Oreochromis aureus | | 3. O. mossambicus. | | Genus sarotherodon | male or female or both responsible for oral incubation of fertilized egg | | | Sarotherodon Galilaeus | ## Substrate Spawner | Def | Description | | --- | --- | | Which make nest in bottom of pond & spawn in them & there is no buccal incubation of fertilized egg | | 1. Tilapia Zilli | | 2. Red tilapia. | Most cultivated spp belong to genus Oreochromis_(specially O. niloticus & O. aureus) bcause of their performance under culture conditions. ## The three major genera are differentiated by the way they brood their eggs and larvae: 1. Tilapias of the genus Tilapia lay their eggs on a substrate, which may be a depression on the pond bottom or tree roots or submerged vegetation. 2. Both parents care for the eggs until hatch. 3. Females fan and clean the eggs with their fins while males guard the territory. 4. Tilapias of the genus Oreochromis lay their eggs in a pit or nest prepared by the males. 5. After the eggs are laid, the female parent incubates the eggs in her mouth. 6. Parental care continues for several days even after the eggs hatch and the fry are free-swimming. 7. Tilapias of the genus Sarotherodon are quite similar to Oreochromis in their reproductive behavior, but both parents or just the male parent are responsible for mouth brooding. 8. Most farmed species of tilapias belong to the genus Oreochromis. ## Species Among the tilapias, members of the genus Oreochromis, such as O. niloticus and O. aureus, are favored in aquaculture because of their performance under culture conditions. | Species | Growth | Critical environmental factors | Suitability | | --- | --- | --- | --- | | O. niloticus | Fastest growing species in many countries. Maximum size 3kg. | Lower lethal temperature = 12° C; does not tolerate high salinity | Highly suitable for farming in tropical, freshwater and brackish water systems. | | O. aureus | Fast growing species. Maximum size -3kg | Tolerates cold temperatures relatively better than most species (lower lethal temperature = 8° C). | Best candidate for farming in subtropical freshwater and brackish water systems. | | O. mossambicus | Fast growth and large maximum size (3kg) observed in wild, but stunting common in culture | Lower lethal temperature = 10°C. Grows well and reproduces under salinities as high as 35%. | Suitability as a pure species is questionable. A good candidate for hybridization if salinity tolerance is desired in the offspring generation | ## Red Tilapia * One of the significant advances in tilapia farming was the development of "red tilapia" * Most tilapias, particularly O. mossambicus, have a dark grey-black skin color. * Their peritoneal cavity is also black in color. * This coloration was deemed unattractive in several markets, resulting in poor acceptance of the fish. * Red tilapias not only lacked the stigma associated with the coloration of the wild-type tilapias, but also resembled premium marine species such as sea bream. * Because pure O. mossambicus red strains had poor growth characteristics, they were hybridized with faster-growing tilapias, such as O. niloticus, O. aureus. There are differences between the strains in: * Growth rate. * Tolerance of low temperature. * Tolerance of high salinity. * Other performance characteristics. * They perform well in saline environments but may have low tolerance of cold temperatures. ## Ecology & Distribution 1. Tilapias live in a wide variety of ecosystems: * Slow-moving parts of rivers. * Floodplain pools. * Swamps. * Lakes. * Coastal lagoons. 2. They are strictly warm water species. 3. They stop growing at temperatures below 16°C and do not survive below 10°C. 4. They survive and grow in brackish waters and many species can tolerate and grow in seawater. 5. Adult tilapias primarily eat plant materials (phytoplankton, benthic algae, macrophytes, etc.) and detritus derived from plant materials. ## Water quality parameter | Water quality parameter | Desirable level | | --- | --- | | Temperature | 26 - 32 °C | | Dissolved oxygen | >1 ppm| | Total ammonia | <1 ppm | | PH | 6.5 - 8.5 | | Alkalinity | >20 ppm | | Hardness | >20 ppm | | Salinity | 0 - 20& | ## Reproductive Biology * All tilapia species mature early (4-6 months). * When mature, tilapias can spawn year-round if the water temperature stays above 24°C. * When a mature Oreochromis female is ready to spawn, the female lays her eggs while the male simultaneously fertilizes the eggs. * The female then picks up the fertilized eggs in her mouth for brooding and leaves the area. * Intensive parental care continues until the fry are large enough to be on their own. * If the fry is threatened, they return to their mother's mouth until the threat passes. * Mouth brooding lasts for 3 weeks, during this time the females can eat little. ## Control Of Reproduction ### 1. Continuous Harvesting Removing the largest fish using a selective net made from natural material or nylon. Thus, by removing the market-sized fish, the remaining young fish are allowed to continue their growth. But it is Labor intensive. ### 2. Stocking predatory fish The most economical method by the small-scale subsistence farmer by stocking predatory fish (as Lates niloticus) together with the tilapia in the pond. These predators will eat most of the tilapia baby fish and will therefore prevent overpopulation of the pond. ### 3. Mono-Sex Populations The early maturation and prolific spawning of tilapias in grow-out systems present two major problems for tilapia farmers. 1. First, physiological energy resources are directed to the processes of sexual maturation and reproduction and become unavailable for somatic growth. 2. Second, continuous recruitment of young tilapias into the grow-out system results in increased competition for resources such as space and food. A number of methods have been developed to control tilapia reproduction and recruitment. The most successful methods involve production of all-male stocks because males grow faster than females in almost all tilapia species. #### Hand-sexing Tilapia males grow faster than females, so they are mostly bigger at the same age. Male tilapia can be distinguished from female tilapia by the absence of an extra opening on the genital papillae. Tilapias display distinct sexual dimorphism as they become juveniles. #### Hybridization Several inter-specific crosses yield high proportion of males (70-100%). Requires maintenance of two pure species breeding lines. Back- crossing or breeding of fish with the parents is also to be strictly avoided. The use of hybridization to produce all-male populations, selecting fish of all one sex by putting two different species of tilapia into a pond. When these fish breed, they produce either a mono-sex culture or a sterile hybrid. The males and females are differentiated by means of their genital morphology: 1. Males have a single longer and pointed opening which serves as the urogenital pore. 2. Females have two round openings, one for urinary excretion and another for expulsion of eggs in the urogenital papillae. 3. This differentiation becomes more obvious when the fish are 10g and larger. As this process is labour intensive and results in wastes of about 50% (females) seed, it is rarely practiced these days. The typical practice is to sex individual tilapias before stocking and select only the males. Hybrids that exhibit commercially advantageous traits relative to their parental species have been developed. For example; O.niloticus × O.aureus hybrid that combines the fast growth of O.niloticus and the cold tolerance of O.aureus. ## Hormonal Sex Reversal Production of genetically male tilapias (GMT) eliminates the need for using hormones to mass produce tilapia seed. 1. The principle behind this method lies on the fact that at the stage when the tilapia larvae are said to be sexually undifferentiated (right after hatching up to about 2 weeks or up to the swim-up stage) the extent of the androgen (male hormone) and the estrogen (female hormone) present in a fish is equal thus, augmenting one of the hormones that is originally present in the fish will direct the fish to either male or female depending upon the hormone introduced. 2. Most commercial all-male tilapia stocks are produced by treating tilapia fry with synthetic androgens, particularly 17a- methyltestosterone (MT). 3. Tilapias can be feminized using estrogens. 4. Non-steroidal estrogens such as ethynyloestradiol and diethylstilbestrol are commonly used. 5. The most commonly used protocol is to incorporate MT into the fry diet at 60 mg/kg of feed by first dissolving it in 95% ethanol. 6. To do this, you need a tank-based or hapa- based hatchery that will allow fry to be collected at the yolk sac or first feeding stages (no later than one week after they have been released from the female). 7. Transferred healthy fry of uniform size to the tank or hapa where you will feed them with hormone-laced diet for 21-28 days. 8. The sex reversal feed is prepared as follows: 9. Mix 30 - 70 mg of hormone (methyl or ethynyl testosterone) in 700 ml of 95% neutral ethanol. 10. Add 700 ml of hormone solution to each kg of finely ground feed then mix thoroughly and dry. At this stage you may add any needed supplements. 11. This feed should be kept under refrigeration if it is not going to be used immediately. 12. Feed the fry at a rate of 10-30% of body weight per day, at least four times a day for 21 - 28 days. 13. The fry must eat this feed to sex-reverse. However, use of hormones in sex reversal evokes environmental and food safety concerns because of the potential for hormones to enter water bodies and the human food chain. Take a sample of fry and sex reverse to females with beta-estradiol -XX females and XY females Progeny test with XY male: * XX female x XY male yields 1:1 sex ratio * XY female x XY male yields 1 XX: 2 XY: 1YY = 1 female: 3 males Take the male progeny XY and YY and progeny test with and XY female from the mother's generation: * XY male x XY female yields sex ratio of 1 female: 3 males * YY male x XY female yields a sex ratio of 1 XY: 1YY = all males Take sample of these fry and sex reverse to female with beta-estradiol -YY and XY females Progeny test with XY males: * XY female x XY male yields a sex ratio of 1 female: 3 males * YY female x XY male yields a genotype ratio of 1 XY: 1 YY = all males Cross YY males with YY females to generate all YY progeny Sex reverse a sample of these YY males to females with beta-estradiol for future brood stock ## Seed Production The simplest and cheapest method is to use fingerlings that result as the by-product of mixed-sex tilapias grow-out in ponds or tanks. (natural reproduction). This system of collecting fry, however, has many drawbacks, mainly: * Inefficiency * Unreliable supply of uniform-size seed. As a result of this inefficient system, development of refined and specialized seed production systems has taken place. These systems may use open ponds, tanks or net cages (hapas) in ponds or large water bodies. | Crosses (x) | Males (%) | | --- | --- | | O. aureus x O. niloticus (Ugadan strain) | 96-100 | | O. aureus x O. niloticus (Stirling strain) | 100 | | O. aureus x O. mossambicus | 100 | | O.hornorum x O. mossambicus | 100 | | O.hornorum x O. niloticus | 100 | | O.hornorum x O. spilurus | 100 | ## Comparison of various Representative Hatchery Systems to Produce Tilapia Fry | | Pond O.niloticus | Tank Florida Red Tiliapias | Hapa O.niloticus | | --- | --- | --- | --- | | Species | O.niloticus | Florida Red Tiliapias | O.niloticus | | System size (m2) | 300-500 | 34 | 40, 60 or 120 | | Stocking density (no./m2) | 1 | 7 | 6 | | Sex ratio (F:M) | 3:1 | 3:1 | 1:1 or 2:1 | | Harvest strategy | Harvest of fry, twice per day | Egg & fry removal Every 15-16 days and artificial incubation | Egg & fry removal every 5-7 days and artificial incubation | | Fry output (no./m2/day) | 7 | 91.7 | 108-141 | | Female productivity (fry/kg female/month) | 82.9 | 3021 | 3180 | ## A. Pond Systems * Earthen ponds are widely used in the production of tilapia fry or fingerlings. * The ponds are typically small (0.01-0.1 ha) and well- managed with fertilization, water- level control and careful feeding. * Brood fish (90-300 g) are stocked at low densities (0.5-1 tilapias/m2) with a male-to-female ratio of 1 to 2-3. * Fry and fingerlings are netted out on a periodic basis (daily, weekly or biweekly) * This type of system may yield fry at a rate of 0.1-3/m2/day. ## B. Tank Systems * Concrete, plastic, or fibreglass tanks are also used in tilapia breeding. * A higher degree of control over the broodstock and seed, as well as the spawning environment, is a major advantage. * Practices such as egg and larvae removal and broodstock reconditioning, which improve hatchery efficiency, can be implemented in tank-based systems with relative ease. * Generally, rectangular tanks are often preferred where size varies from small to big (2.0-10.0 m long; 2.0-4.0 m wide with a depth of 0.8-1.0 m) * Brood fish (100-200 g) are stocked at densities of -14 brooder/m2(with a male-to-female ratio of 1 to 3 (1:2-7) * Egg and Fry collected every 10-14 days. * Seed production up to 400-3,000 fry/ m2/month or 200-1,500 fry/female/month can easily be achieved. The main disadvantage of tank systems is the high cost of initial investment to construct them. ## C. Hapa Systems Hapa-based breeding systems provide some of the advantages of tank-based systems at a lower cost. * A hapa is a cage made of netting that can be suspended in ponds, tanks or large water bodies such as lakes and reservoirs. * Brood fish are stocked inside the hapa. * Eggs and larvae are regularly collected. * Hapas sizes vary but the ideal size measures 3 m long, 3 m wide, and 1.5 m deep. * Stock the brooders (100 to 200 g ) at a density of 4 - 5 brooders/m with a male-to-female ratio of 1 to 1-2. * Egg and Fry collected every 10-14 days. Seed production up to 100 fry/ m2/day. ## Nursing Of Tilapia Fry The nursery phase involves growing the young fry to fingerling size in nursery ponds. ### In earthen pond * The nursery ponds are approximately 0.4 -0.6 ha. * Nursery ponds are stocked at very high densities of 240,000 to 300,000 per hectare. * Fry are fed a floating pelleted supplemental ration in a regime based on percentage of body weight for a period of 6-8 weeks. * The fish achieve fingerling size, 15 to 25 grams, at which time they are stocked in the grow-out or production units. * Nursing of tilapia fry. ### In Tank * For one week, stocking of the fry can be kept as 1000-1200 per m2 and they are fed with powdered pelleted feed containing high protein (minimum 35 up to 45%), at a rate of 15-20% of the biomass 4-6 times/day. * During the second week, density of the fry is reduced to 500-600 per m2 with feeding rates of 12-15% of the biomass. * After another week, stocking of the fry density is again reduced to 300-400/m2 with feeding rates of 10-12% of the biomass. * Usually, fry are reared until they reach to approximately 5g in weight, then transferred to fingerling tanks for further growth. * In fingerling rearing tanks, the fry weighing 5-20 g may be stocked at a rate of 1,600 fries/ m2 whereas 20-50 g at 1,000 fries/m2. ## Grow-Out Culture Systems & Feeding. | | Extensive | Semi-intensive | Intensive | Super-intensive | | --- | --- | --- | --- | --- | | Stocking density (no. of animals/m² or m³) | ~1 | 2-5 | > 5 | > 20 | | Source of seed (fingerling) for stocking | Wild fish, by-product of culture | Own or commercial hatcheries. | Own or commercial hatcheries. | Own or commercial hatcheries. | | Reproductive control | None | All-male stock may be used | All-male stock | All-male stock | | Fertilization | None except incidental, run-off fertilisation | Manure and inorganic fertilisers applied | None | None | | Feeds | None except occasional farm by-products and household wastes | Farm by-products such as rice bran, oilseed cakes or supplementary compound feeds | Complete, compounded feeds. | Complete, compounded feeds. | | Aeration/water exchange | None | Limited, occasional water exchange | Used frequently | Highly | | Culture duration | Seasonal | 6-9 months | 4-6 months | 4-6 months | ## Yield (mt/ha/crop) | | ~1 | 1-5 | 5-20 | >20 | | --- | --- | --- | --- | --- | | Market | Producers' own consumption and local, rural markets | Local and national, export markets | Urban, high value, export markets | Urban, high value, export markets | | Extensive tilapia culture system | | | | | | Semi-intensive tilapia culture system | | | | | | Intensive tilapia culture system | | | | | | Super intensive tilapia culture system | | | | | ## Tilapia Culture Systems In Egypt Nile tilapia are reared both: 1. semi-intensively in earthen ponds 2. and intensively in cages, ponds and concrete tanks, 3. and in integration with terrestrial crops. ### Semi-intensive production system Under the semi-intensive production system, both tilapia monoculture and polyculture with carps and mullets are commonly practiced. Stocking densities vary significantly, depending on pond size, depth, initial fish size and culture conditions. – Tilapia pond fertilization with organic and inorganic fertilizers has been widely adopted, but this practice is diminishing because many farmers have abandoned pond fertilization, and currently depend mostly on commercial tilapia feeds. Both extruded (floating and sinking pellets) and pressed feeds (25-30 percent crude protein) are used. Manual feeding and demand feeders are commonly used for feeding farmed tilapia. The yield ranges from 5-9 MT/hectare/cycle, depending on initial fish size, stocking densities, water quality and feed and feeding management. ### Intensive production system Intensive culture of Nile tilapia in floating cages is also widely practiced. The fish are stocked in floating cages at a density of 60 to 100 fish/m3 to yield 25 to 40 kilograms/m3 . Intensive tilapia culture in earthen ponds, tanks and recirculating systems is slowly spreading in Egypt. Nile tilapia (2 to 20 grams) are stocked in the ponds at a density of 50,000 to 100,000 fish/ha. The ponds and tanks are provided with aeration and processed feeds. The fish grow to 200 and over 300 grams in five to eight months, yielding from 15 to over 20 MT/ha. ## Feeding of tilapia in farms ### 1. Model tilapia feed formulations : | | Semi-intensive ponds (26% protein)| Intensive ponds (32% protein) | Intensive tanks (36% protein) | | --- | --- | --- | --- | | Soybean meal | 38.3 | 48.5 | 50.8 | | Wheat middlings | 4 | 20 | 18 | | Fishmeal | 4 | 6 | 12 | | Corn | 50.8 | 22.6 | 16.5 | | Dicalcium phosphate | 1 | 1 | 0.8 | | Vegetable oil | 1.5 | 1.5 | 1.5 | | Vitamin mix | 0.2 | 0.2 | 0.2 | | Mineral mix | 0.2 | 0.2 | 0.2 | ### 2. Feed forms and particle sizes recommended for tilapias : | Body size (g) | Particle size diameter (mm) | Recommended form | | --- | --- | --- | | <1 | 0.5-1 | Meal | | 1-2 | 1-1.5 | Crumbles | | 2-30 | 1-2 | Crumbles | | 30-100 | 2.4 | Pellets/extruded particles | | 100-250 | 3.2 | Pellets/extruded particles | | 250 to market size | 4.8 | Pellets/extruded particles | ### 3. Feeding allowance and frequency for tilapias at different body sizes: | Body size (g) | Daily feeding allowance (% of body weight) | Feeding frequency (no. of meals/day) | | --- | --- | --- | | > 1 | 30-10 | 8-12 | | 1-5 | 10-6 | 6 | | 5-20 | 6-4 | 4 | | 20-100 | 4-3 | 3-4 | | > 100 | 3-2 | 2-3 | ### 4.. Feeding allowance as modified by water temperature: | Temperature (°C) | % of normal daily feeding allowance | | --- | --- | | 32-35 | 80 | | 24-32 | 100 | | 22-24 | 70 | | 22-20 | 50 | | 20-18 | 30 | | 18-16 | 20 | | More than 16 | No feeding | ## Special Problems ### A. Over-wintering of tilapia fingerlings The tropical/subtropical origins of Nile tilapia are obviously reflected in their thermal tolerance as these fish do not grow well at temperatures below 16 °C and cannot survive for more than a few days below 10 °C. In order to maximize Nile tilapia yields, juveniles (≈50 g) when transferred to production ponds in the spring will not reach market size fish in the summer, so instead, they should be stocked during the winter season. Overwintering of tilapia fingerlings can be made through: 1. Fingerlings can be held in small ponds with water depth of 2-3 m. 2. Fingerlings can be overwintered in long, narrow ponds that are covered with clear plastic if the winter is mild. 3. In greenhouses and heated buildings, recirculating systems are used to hold large quantities of fingerlings. 4. Fingerlings can be held in cages located in geothermal springs or in small ponds or tanks through which warm spring water is diverted. ### B. Over-population of tilapia Failure of tilapia culture in the past, has often been due to uncontrolled spawning, resulting to the production of large numbers of fry and stunted populations. This is due the fact that, tilapia attains maturity at an early age before reach marketable size and breed repeatedly at short intervals, over populating grow out ponds. There are basically a number of methods of controlling tilapia populations: 1. Monosex culture. 2. Periodic harvesting of tilapia fry and fingerlings. 3. Culture of fish in cages. 4. Culture at very high densities. (It works on the principle that crowding reduces the urge to reproduce) . 5. Biological control: by stocking predacious fish (2-10% of stock) as fingerlings or adults in a pond. Predator species such as Nile perch Lates niloticus, Clarias lazera and Dicentrarchus spp. have been used for this purpose. Rearing of duck ( extensive system) on the tilapia pond. ## Some important questions **Complete the following :** 1. Tilapia can be classified according to breeding behavior into 2 groups... **Mouth brooder and Substrate Spawner** 2. Most cultivated spp belong to genus Oreochromis_(specially O. niloticus & O. aureus) bcause **of their performance under culture conditions.** 3. When a mature Oreochromis female is ready to spawn, the female **lays her eggs** while the male **simultaneously fertilizes the eggs.** 4. Control of reproduction is done by **the female picking up the fertilized eggs in her mouth for brooding and leaving the area.** 5. Mono-sex production of tilapia is done by **using hormones to mass produce tilapia seed** **Write on:** 1. Special problems of tilapia culture. 2. Hapa system. 3. Reproductive biology of tilapia. 4. Causes of success of tilapias as a farmed fish.