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By Dr Mark Burdass, Sparsholt college.

By Dr Mark Burdass, Sparsholt college.

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  • 1. Tilapia Husbandry Mark Burdass
  • 2. Key Areas • Water Quality • Systems • Stock Management • Feeding • Disease monitoring
  • 3. Water Quality • Tilapia are very tolerant to poor water quality • Often quoted as very tolerant to typically lethal WQ parameters for other fish • For Example – Tolerant to DO levels of 0.1mg/l – Tolerant to Total Ammonia Nitrogen of 16mg/l – Tolerant to Nitrite levels of 25mg/l • However, what’s not mentioned is the massive effect on behaviour and production performance these poor WQ parameters have!
  • 4. Xu, Liu, Cuic and Miao, 2006
  • 5. Water Quality • To maintain good production efficiencies then the following should be targets. • DO Levels above 4mg/l preferably above 5mg/l • CO2 levels should be kept below 5mg/l (for every mg of oxygen used the fish excrete 1.4mg of CO2) • TAN levels below 1mg/l (<0.1mg/l UIA) – Peak ammonia excretion is around 1 -5 hours after feeding • Nitrite levels below 1mg/l
  • 6. Water Quality • High suspended solids (SS) levels are often a consequence of feeding in intensive systems. • Tilapia (Oreochromis sp are filter feeders) and so are very tolerant of high SS, and can take levels well over 500mg/l • However, need to be kept low (below 50mg/l) as strongly associated with chronic disease problems if allowed to persist
  • 7. Water Quality • Temperature • One of the single most important parameters for influencing growth • Tilapia are very cold intolerant • They become inactive below 16oC • Feeding is strongly reduced below 20oC • Sensitive to rapid temperature changes of more than 4oC per day
  • 8. Water Quality • Even above 20oC there are consequences for low temperatures • Optimum temperatures are around 28oC for O.niloticus. • Temperatures below this have impacts on growth performance.
  • 9. Water Quality El-Sayed & Kawanna, 2008
  • 10. Water Quality Impact of temperature on % weight gain over 50 day trial on O. niloticus fry 6000 5000 % weight gain 4000 3000 % Wt gain 2000 1000 0 20 25 30 35 Temperature (o C) Impact of temperature on FCR over 50 day trial on O. niloticus fry Impact of temperature on Cumulative Specific Growth rate over 50 trial on O. niloticus fry 4 8 3.5 3 7.5 2.5 7 FCR 2 FCR SGR 6.5 SGR 1.5 1 6 0.5 5.5 0 20 25 30 35 5 o 20 25 30 35 Temperature ( C) Temperature (o C)
  • 11. Water Quality • Sub optimal temperatures also has an impact on the immune system • Tilapia will potentially become more susceptible to disease organisms they would normally shrug off!
  • 12. Photoperiod • Long photoperiods produce best results for tilapia • 18L:6D seems to give very good results for growth • Needs to be considered during the winter months
  • 13. Water Quality • Water flows should be maintained to allow self cleaning and maintain WQ • However, tilapia are not trout! Keep flow rates below 5cm/sec • If water flows are too high they will expend a lot of energy swimming and not growing
  • 14. Water Quality • Salinity • Tilapia are generally a salt tolerant species, tolerating levels over 15 ‰ • This can be advantageous as could be used as a general prophylactic treatment against external parasites • Has also been used to improve carcass quality
  • 15. Systems • Hatchery Systems • Eggs need to be kept moving • Eggs should be incubated in McDonald jars • Yolk-sac fry can also be incubated this way
  • 16. Systems • In intensive systems usually held in circular tanks or raceways • For fry production raceways are advantageous as they have a better surface to volume ratio – Reduces feeding competition between fry for the floating food • For on-growing tilapia round tanks or D ended raceways give better flow dynamics and self cleaning. These types of tank also reduce aggression as there are no corners!
  • 17. Systems
  • 18. Stock Management • Adult tilapia are a robust cichlid capable of taking high levels of handling with minimal physical damage • However, fry are sensitive to handling. • Also any handling will reduce growth performance because of the stress induced • Keep handling to a minimum, this also reduces risk to staff!
  • 19. Stock Management • Tilapia will readily form aggressive size hierarchies that can lead to aggression and so stress. • To keep this to a minimum, ensure that the fish at the start of a production cycle are very similar in size • Regular grading ensures that size hierarchies are kept to a minimum • Keep early stocking densities relatively low (20kg/m3) • This reduces aggression and also improves growth potential of the fish during the start of the production cycle
  • 20. Stock Management • Grading can be done with bar graders though when they raise their fins they can get stuck! • It’s important to maintain reasonably uniform size as the growth of the smallest fish will be depressed by the more dominant larger fish • Some farms just grade by eye
  • 21. Stock Management • Stocking densities are really dictated by system capacity • If oxygen is not being used then levels of 40kg/m3 are relatively easy to obtain • If oxygen is being used then levels of over 60kg/m3 are possible • However, a simple rule of thumb is to start relatively low to increase growth potential and maximise FCR and SGR • Increase stocking densities as production cycle progresses • Respond to deteriorating water quality parameters • Poor water conditions may be tolerated by tilapia but they will cause stress and so increase disease risk
  • 22. Feeding • Tilapia (Oreochromis) are plankton grazers not predators! • This means that they are best fed with multiple meals during the day • Feeders need to be able to ensure even food distribution. – Poor feeding can lead to uneven stock growth and aggression • Feeding by hand or good automatic feeders can be effective • Pellet size is important, they generally prefer much smaller pellets compared to salmonids.
  • 23. Feeding • Tilapia will chew pellets so don’t be tempted to overfeed. It can be easily done! • Feeding times Size % BW per day Feed Frequency (per day) First feed – 1g 30 - 10 8 1 – 5g 10 - 6 6 5 – 20g 6-4 4 20 – 100g 4-3 3-4 >100g 3 3
  • 24. Disease monitoring • Tilapia are pretty hardy in terms of disease • However, like most fish if they get stressed they can get diseases. • To avoid stress make sure that: – Maintain a good WQ regime – Well graded stock maintenance – Limit handling and minimise handling stress – Reasonable stocking densities – Good quality food – Good feeding regime • Some evidence that probiotics in the feed can maintain health in tilapia
  • 25. Disease monitoring • What to look for: • Behavioural clues – Flashing – Erratic swimming – Poor appetite – Lethargy and loss of escape reaction – Jumping – Rapid opercular movements • Physical clues – Dark skin – Eroded fins – Mortality – Exophthalmia – Gill discolouration – Excess mucus production
  • 26. Conclusion • Tilapia are a good aquaculture species • Good growth rates are possible • Very forgiving in terms of tolerances • However, like all fish they get stressed • Stress is a manageable phenomenon • Maintaining a low stress environment by good husbandry is the key to successful production
  • 27. Thank you