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

Effect of bottleneck can be illustrated in the example below.Example 3: If a farmer is trying to maintain a constant Ne of 344 for 10 generations in order to produce aguarantee of 99% for keeping an allele at frequency of 0.01 and there is a bottleneck of 25 in the 8 th generation,estimate the probability of losing the allele when the 10 th generation is produced.• Step 1 and 2:N e Probability of losing allele (P) Guarantee of keeping allele (1-P)344 (1-0.01) 2*344 0.999006852344 (1-0.01) 2*344344 (1-0.01) 2*344 0.999006852344 (1-0.01) 2*344 0.999006852344 (1-0.01) 2*344 0.999006852344 (1-0.01) 2*344 0.999006852344 (1-0.01) 2*344 0.99900685225 (1-0.01) 2*25 0.394993932344 (1-0.01) 2*344 0.999006852344 (1-0.01) 2*344 0.999006852• Step 3:Guarantee of keeping allele after 10 generations = (0.999006852) 9 *0.394993932= 0.3915• Step 4:Guarantee of losing allele after 10 generations = 1 – 0.3935 = 0.6085As such, the bottleneck of 25 at generation 8 increased the probability of losing the allele in the 10 th generationfrom 0.01 (which was the goal) to 0.6085.ConclusionGenetic management in hatchery is although simple but has not been implemented adequately and scientifically ina majority the ASEAN member countries. This is because most hatchery managers are poorly trained in geneticsand as such it is neglected in the hatchery development plan. Also because not many hatcheries keep record ofperformance of the seed they produce, the effect of inbreeding if occurred would not be able to monitor orvisualised. It is essential that the importance of genetic management be recognised and action is taken at thehatchery level to ensure the long-term supply of good quality seed. Needless to say this needs to go hand in handwith good aquaculture husbandry and developments in nutrition or fish health.42