Principles of Genetics and Breeding

Answers

1. Ne=67.95

If the sex ratio is 1:1 then Ne=78

Farmer need to maintain 101 females and 101 males to produce an Ne of 100.

2. Step 1.How many food fish must be harvested to produce 200 select fingerlings, if you save the top 10%?

Number of food fish harvested = number saved/percent saved = 200/0.1 = 2,000.

Step 2. How many select fingerlings should be stocked in the food fish pond, if mortality is 10%?If mortality is 10%, survival is 90%:

Number of fingerlings stocked = number harvested/survival rate = 2,000/0.9 = 2,223.

Step 3. How many fingerlings must be harvested from the fingerling pond to produce 2,223 select fingerlings, if you save the top 50%?

Number of fingerlings harvested = number saved/percent saved = 2,223/0.5 = 4,446.

Step 4. How many fry must be stocked in the fingerling pond to produce 4,446 fingerlings, if mortality is 50%? If mortality is 50%, survival is 50%:

Number of fry stocked = number harvested/percent survival = 4,446/0.5 = 8,892.

Step 5. How big should the fingerling pond be, if it is stocked at 200,000/ha and if you will stock8,892 fry?

Size of fingerling pond = number of fry that will be stocked/stocking rate =8,892/200,000 = 0.0446 which is rounded to 0.045 ha.

Step 6. How big should the food fish pond be, if it is stocked at 7,000/ha and if you will stock2,223 fingerlings?

Size of food fish pond = number of fingerlings that will be stocked/stocking rate =2,223/7,000 = 0.3175 ha which is rounded to 0.318 ha.

4. Step 1. Calculate the selection differential (S).
S = mean length of the select brood fish - mean length of the population
S = 162 mm - 146 mm = 16 mm

Step 2. Calculate the predicted response to selection (R).
R=Sh²
R=(16mm)(0.26)
R = 4.16 mm

Step 3. Calculate the mean of the F₁, generation of select fish.
mean of the F₁ generation = mean of the population + R
mean of the F₁ generation = 146 mm + 4.16 mm = 150.16 mm

5. Total improvement is calculated as follows:
Total improvement			= (mean length of F1 select generation - mean length of P1 generation)
			= 165 mm - 150 mm = 15 mm
Environmental gain is calculated as follows:
Environmental gain			= (mean length of F1 control generation - mean length of P1 generation)
			= 159 mm - 150 mm = 9 mm
Genetic gain is calculated as follows:
Genetic gain		= (mean length of F1 select generation - mean length of F1 control generation)
		= 165 mm - 159 mm = 6 mm
or
Genetic gain		= (total improvement - environmental improvement)
		= 15 mm - 9 mm = 6 mm