Ef f ects of rearing conditions Ef f ects of rearing conditions - PowerPoint PPT Presentation

Ef f ects of rearing conditions Ef f ects of rearing conditions on low- - temperature tolerance temperature tolerance on low of Nile tilapia, Oreochromis Oreochromis of Nile tilapia, niloticus, , juveniles juveniles niloticus By By H. Charo H. Charo- - Karisa, M. A. Rezk, H. Bovenhuis & H. Komen Karisa, M. A. Rezk, H. Bovenhuis & H. Komen From From Fish Culture and Fisheries & Animal Breeding and Genetics Group, WI AS, WI AS, Fish Culture and Fisheries & Animal Breeding and Genetics Group, Wageningen University, The Netherlands Wageningen University, The Netherlands The World Fish Center, Abbasa Abbasa, , Abou Abou Hammad Hammad, Egypt , Egypt The World Fish Center, Kenya Marine and Fisheries Research I nstitute, Box 136, Pap- - Onditi Onditi, Kenya , Kenya Kenya Marine and Fisheries Research I nstitute, Box 136, Pap

Background information Background information ! Global expansion of tilapia farming Global expansion of tilapia farming ! constrained by sensitivity to low temperature constrained by sensitivity to low temperature ! Optimal growth temperature: 25 Optimal growth temperature: 25- - 28°C 28°C ! ! Over Over- - wintering mortalities common wintering mortalities common ! ! Cold tolerance in fish dependent on Cold tolerance in fish dependent on ! • Environment Environment • • Health and nutrition Health and nutrition • • Genetic effects Genetic effects • ! Selection for growth in low input Selection for growth in low input ! environments at Abbasa Abbasa, Egypt , Egypt environments at ! Improvement of trait important for extension Improvement of trait important for extension ! of grow- - out period out period of grow

Objectives Objectives ! Investigate the effect of age, genotype and Investigate the effect of age, genotype and ! body size on cold tolerance (Experiment 1) body size on cold tolerance (Experiment 1) ! Investigate effect of diet on cold tolerance Investigate effect of diet on cold tolerance ! (Experiment 2) (Experiment 2) ! Determine low lethal temperature for Determine low lethal temperature for O. O. ! niloticus reared under low reared under low- -input input niloticus environments (Experiment 1 and 2) environments (Experiment 1 and 2) ! Determine the effect of acclimatization on Determine the effect of acclimatization on ! cold tolerance (Experiment 1 and 2) cold tolerance (Experiment 1 and 2)

Experiment 1 Experiment 1 ! Fry families produced and Fry families produced and ! grown in separate 2x3 m grown in separate 2x3 m hapas in pond until tagging hapas in pond until tagging ! Pond received 50kg/ ha Pond received 50kg/ ha ! chicken manure per day chicken manure per day ! Carried out in summer Carried out in summer ! ! 10 fry/ family from 80 10 fry/ family from 80 ! families tagged families tagged ! Age range from 41 Age range from 41- - 90 days 90 days ! ! Weight: 1 Weight: 1- - 20g 20g !

Cold tolerance test Cold tolerance test Chiller ! Experiment in cold room and Experiment in cold room and ! 5 aquaria 5 aquaria ! Water temperature lowered from 16 °C at the rate of 1°C/day ! Fry not fed Fry not fed ! ! Hourly measurements of Hourly measurements of ! temperature and mortality temperature and mortality ! Trait description: Trait description: ! Temperature at Death (TAD) Temperature at Death (TAD) or Cooling Degree hours or Cooling Degree hours (CDH) (CDH)

Experiment 2 Experiment 2 ! Carried out in Fall Carried out in Fall ! ! 20 full 20 full- - sib families produced using sib families produced using ! brooders in first experiment brooders in first experiment ! Each family divided in two groups Each family divided in two groups ! of 30 swim - - up fry up fry of 30 swim ! Assigned to two treatments: Assigned to two treatments: ! pellet and natural- - fed fed pellet and natural ! Reared for 42 days Reared for 42 days ! ! 10 fish per treatment per family 10 fish per treatment per family ! tagged for cold tolerance tagged for cold tolerance ! Cold tolerance measured as in Cold tolerance measured as in ! experiment 1 experiment 1

Data analysis Data analysis ! Genotype, aquarium, age, size analyzed Genotype, aquarium, age, size analyzed ! in experiment 1 in experiment 1 ! Model 1: Model 1: ! Y ijkl = µ + a a i + β β 1* 1*AGE AGE ijkl β 2* 2*ln(w) ln(w) ijkl +s s j + d d k (s j ) + e e ijkl Y ijkl = µ + i + + β ijkl + j + k (s j ) + • • ijkl + ijkl ! Effect of diet, genotype, aquarium, Effect of diet, genotype, aquarium, ! specific growth rate, condition factor and and specific growth rate, condition factor genotype X diet effects analyzed in analyzed in genotype X diet effects second experiment second experiment ! Correlation of size and cold tolerance Correlation of size and cold tolerance !

Results Results Fish that lost balance (arrows) considered dead

Results Results ! Mortality in experiment 1 from 13.6°C to 8.6 °C Mortality in experiment 1 from 13.6°C to 8.6 °C ! ! Experiment 2: from 11.7 °C to 7.5 °C Experiment 2: from 11.7 °C to 7.5 °C ! 100 Experiment 1 90 Experiment 2 Cumulative percent mortality 80 70 60 50 40 30 20 10 0 5 5 5 5 5 5 5 4 3 2 1 0 9 8 7 . . . . 1 1 1 1 1 . . . 3 2 1 0 9 8 7 1 1 1 1 Temperature (°C)

Size and cold tolerance parameters Size and cold tolerance parameters of pellet and natural- -fed tilapia fry fed tilapia fry of pellet and natural Parameter Diet Pellet-fed Natural-fed P-value Initial weight (g) 0.045(0.03) 0.045 (0.03) - Final weight (g) 1.97 (0.65) 1.92 (0.61) 0.4771 Standard length (mm) 38.05 (3.99) 37.58 (3.81) 0.2239 Specific growth rate (%/day) 9.37 (1.21) 9.34 (1.29) 0.8659 Condition factor 3.86 (0.40) 3.71 (0.37) 0.0002 Temperature at death (ºC) 8.9 (0.67) 9.0 (0.64) 0.0348 Cooling degree hours 551.66 (104.53) 530.56 (99.80) 0.0414

Tendency for smaller fish to have lower Tendency for smaller fish to have lower cold tolerance cold tolerance 500 y = 86.662Ln(x) + 165.31 R 2 = 0.3365 450 400 Cooling Degree Hours 350 300 250 200 150 100 50 0 0 5 10 15 20 25 Body weight (g)

Presence of genotype environment Presence of genotype environment interaction interaction 800.0 Pellets 700.0 Manure 600.0 Cooling Degree Hours 500.0 400.0 300.0 200.0 100.0 0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Family

Results and Discussion Results and Discussion ! Significant effect of aquarium, Significant effect of aquarium, ! genotype, fish size in both genotype, fish size in both experiments experiments ! Age does not affect tolerance Age does not affect tolerance ! ! Pellet Pellet - - fed fish significantly more cold fed fish significantly more cold ! tolerant than natural (phytoplankton) tolerant than natural (phytoplankton) fed fish fed fish ! Fish reared in autumn more cold Fish reared in autumn more cold ! tolerant tolerant • Acclimatization effect ? Acclimatization effect ? •

Acclimatization Acclimatization ! Mortality in experiment 1 from 13.6°C to 8.6 °C Mortality in experiment 1 from 13.6°C to 8.6 °C ! ! Experiment 2: from 11.7 °C to 7.5 °C Experiment 2: from 11.7 °C to 7.5 °C ! 100 Experiment 1 90 Experiment 2 Cumulative percent mortality 80 70 60 50 40 30 20 10 0 5 5 5 5 5 5 5 4 3 2 1 0 9 8 7 . . . . 1 1 1 1 1 . . . 3 2 1 0 9 8 7 1 1 1 1 Temperature (°C)

Temperature regimes during fry Temperature regimes during fry rearing in the two experiments rearing in the two experiments (a) 31 29 Temperature (ºC) 27 25 23 21 19 Min. Experiment 1 17 Min. Experiment 2 15 (b) Time (days) 35 33 31 T em p eratu re (°C ) 29 27 25 23 21 Max. Experiment 1 19 Max. Experiment 2 17 15 Time (days)

Conclusions Conclusions ! Smaller (< 5g) fish are less tolerant to lower temperatures ! Potential for manipulation of Potential for manipulation of ! environment and diet for improved environment and diet for improved cold tolerance cold tolerance ! Genotype x diet interactions should Genotype x diet interactions should ! be further studied be further studied

Acknowledgements Acknowledgements ! INREF INREF- - POND POND ! ! World Fish Center World Fish Center ! ! Tilapia International Foundation (TIF) Tilapia International Foundation (TIF) ! Thank You All! Thank You All!