Training of Trainers - Library - Network of Aquaculture Centres in ...

More documents

Recommendations

Info

Where F is the percent increase in homozygosity or the amount of inbreeding produced (0-100%) in a singlegeneration. This formula shows that when Ne decreases F increases and vice-versa. Ne that are less than 50produce large amount of inbreeding per generation (Figure 1).0.300.250.20F 0.150.100.050.002 4 8 16 32 64 128 256 512N eFigure 1. Relationship between N e and F. F is the inbreeding (percent increase in homozygosity) producedin once generation in a population with no previous inbreeding.In a closed population once inbreeding has occurred, it lowers the N e of the next generation:N eN eF =1+ FWhere N eF is the effective breeding number in a closed population with F>0%. For practical purposes, the total F isproduced over a series of generations can be calculated by summing the F that is produced in each generationwithout considering previous inbreeding.So how large N e should be to minimise inbreeding? There is no rule of thumb of how large N e should beunfortunately. This depends on the purpose/goal of the hatchery (Figure 2).Figure 2. N e needed per generation to produce F of 1%, 5% and 10% after 1-50 generations.39
For small hatcheries, it may be difficult to manage inbreeding but they should be encouraged to do so. Ifhatcheries maintain a constant Ne = 50 for 5 generations, they will keep F ≤5%. This recommendation producesgood short term (5 generations) management and is not excessive.Techniques to improve Ne include:• Increase number of brood stock that can spawn and provide viable offspringGenetic drift• Keep male: female ration as close to 1:1 as much as possible.• Apply pedigree mating: each male leaves a son and each females leave a daughter as brood stock forfollowing generation (can be more than one but as long as all leave the same number).• Number of offspring used for potential brood stock should be equal among families.• Milt should not be pooled or added in a sequential manner. These practices cause gametic competition andone male can fertilise most of the eggs, producing N e much less than expected.• Stretch the time of replacing brood stock: The desired N e shown in Figure 2 is given in number of generations,not number of years. If the goal is to keep inbreeding below a given value for 20 years and the normalprocedure is to use a 2-year generation interval, 10 generations will be produced during the 20-year plan. But ifgeneration interval could be stretched to 3 years, could be 7 generations would be produced during the 20years, which means a smaller N e could be used to achieve the desired goal.• Procure new brood stock from a different source. If 10-15% new brood stock are introduced each generation,the amount of inbreeding can be drastically reduced.• Maintain two unrelated populations and produce hybrids (or swapping brood stock with other hatcheries).Genetic drift is the random changes in gene frequency – changes that are not due to selection, migration ormutation. The causes can be natural e.g. a sudden raise of temperature due to fire at one stretch of the river thatkills a large number of fish, or could be anthropogenic causes such as the way fish are collected as foundationpopulation.Genetic drift will ultimately lead to the loss of genetic diversity. When procuring fish for broodstock for example,often only a small portion of a population is collected that causes a condition called founder effect – where geneticdrift creates a population in which the gene frequencies are markedly different from those of the originalpopulation.Similar to inbreeding, genetic drift is inversely related to Ne – the smaller Ne the more chance that genetic driftchanges the allele frequencies (i.e. one genetic form will be gradually lost). The probability of losing an allele viagenetic drift in a single population is illustrated in Figure 3.Recommended N e to minimise genetic drift range from 500-5,000 with 500 being the most common. Methods todetermine based on percent guarantee and allele frequencies can be illustrated in Example 2.Example 2: You want to save alleles (frequency q = 0.01) and 95% guarantee of saving the allele (P=0.05) after10 generations. What constant Ne is needed to achieve this goal?• Step 1: Calculate guarantee per generation (G) that is needed to produce a guarantee after 10 generationso 0.95 = G 1040
Page 1 and 2: Training of TrainersProgramme3-7 Au
Page 3 and 4: Table of Contents1. Preface 42. Sen
Page 5 and 6: knowledge about the activities carr
Page 7 and 8: iosphere, in that it is essentially
Page 10 and 11: Importance in narrowing the supply
Page 12 and 13: Figure 7: The trend in aquaculture
Page 14: aquaculture has been a success thus
Page 17 and 18: pathogen transfer is generally cons
Page 19 and 20: • It highlights the importance a
Page 21 and 22: particular animal are identified, t
Page 23: Knowledge at the bottom of the pyra
Page 26 and 27: farmer innovation process. In this
Page 28 and 29: • Rapport building• Working str
Page 30 and 31: shrimp farming is undertaken in the
Page 32 and 33: Reintjes, C and Hiemstra, W. 1989 F
Page 34 and 35: • An increase in reliable product
Page 36 and 37: Principles of AACC are to: 1) Facil
Page 38 and 39: Maintaining genetic quality of fish
Page 42 and 43: o G=(0.95) 1/10G =0.994883803Figure
Page 44 and 45: Aquaculture extension and training
Page 46 and 47: ResearchExtensionFarmersFlow of inf
Page 48 and 49: view of outside world than before a
Page 50 and 51: Along with fish sample, the support
Page 52 and 53: Fungal examinationFungal infection
Page 54 and 55: few different pathogen strains. The
Page 56 and 57: Major finfish diseases in Asia and
Page 58 and 59: A great number and diversity of ani
Page 60 and 61: • -oxidase test positive• -resi
Page 62 and 63: ReferencesAustin, B. and D. Austin.
Page 64 and 65: Accessing better markets-improving
Page 66 and 67: Owing to its importance in generati
Page 68 and 69: adopt standards for responsible shr
Page 70: Tokrisna R, Benheam W., 1995. Gain
Page 73 and 74: of the temperature rise that were d
Page 75 and 76: Principles of developing, validatin
Page 77 and 78: such as determinants, exposures and
Page 79 and 80: How to promote adoption of BMPs?Pro
Page 81 and 82: economic sustainability. BMPs need
Page 83 and 84: Once you understand your stakeholde
Page 85 and 86: As conventional approaches such as
Page 87 and 88: Printed publicationsPrinted publica
Page 89 and 90: Set up a blog or website for your w
Page 91 and 92:
If you have a website, all you need
Page 93 and 94:
ought about increased profits among
Page 95 and 96:
• It is a farming system the prod
Page 97 and 98:
Annex 1. The area surveyed for obta
Page 99 and 100:
contribute substantially to maintai
Page 101 and 102:
seawater, but in fresh water its le
Page 103 and 104:
type of ingredients used, since som
Page 105 and 106:
This is a new approach used to buil
Page 107 and 108:
New, M.B., A. G. J. Tacon and I. Cs
Page 109 and 110:
later stages it has become a much m
Page 111 and 112:
c. Improved information exchange an
Page 113 and 114:
implemented by both societies. Inte
Page 115 and 116:
With better informed farmers, the s
Page 117 and 118:
According to FAO, it is estimated t
Page 119 and 120:
Farmer organization as models for p
Page 121 and 122:
NaCSA disseminates BMPs mainly thro
Page 123 and 124:
1. Drain the pond water completely
Page 125 and 126:
Seed transportation and Stocking:
Page 127 and 128:
7. Presently 100% of the society po
Page 129 and 130:
would help in sustaining shrimp sec
Page 131 and 132:
Stress brought about by the capture
Page 133 and 134:
Enhance women participation in aqua
Page 135 and 136:
women in aquaculture and identify a
Page 137 and 138:
major percentage of staff, the need
Page 139 and 140:
having more self confidence through
Page 141 and 142:
Overall status of men and women in
Page 143 and 144:
Compliance to international standar
Page 145 and 146:
(ii) to protect human or animal lif
Page 147 and 148:
c) FAO/WHO Codex Alimentarius Commi
Page 149 and 150:
Annex 1: List of participantsCountr
Page 151 and 152:
Annex 2: AgendaDate Time Presentati
Page 153:
Annex 3: List of resource persons1.
show all

Training of Trainers - Library - Network of Aquaculture Centres in ...

Create successful ePaper yourself

Delete template?

Save as template?