9585

• UCREFRP Catalog Number: 9585
• Author: U.S. Fish and Wildlife Service.
• Title: Inland Salmonid Broodstock Handbook.
• USFW Year: n.d.
• Copyright Material: NO

Effective Breeding Number
The effects of mating a given number of females and a given number
of males on effective population number can be estimated by using
the following formula:
EN = 4 X (NF) X (NM)
NF + NM
Where: EN = Effective Number
NF = Number of Females
NM = Number of Males
Consider the effects of founding a broodstock using 99 females and
1 male or using 2 females and 2 males. Remember that each sex
contributes one half of the genetic material to the next
generation.
99 females and 1 male
EN = 4 x L99) x (ll = 396 = 3.96
99 + 1 100
2 females and 2 males
EN = 4 x L~) x (2~ = 16 = 4.00
2 + 2 4
The effective breeding number far 99 females and 1 male, and for 2
females and 2 males, is virtuaYly the same. Hence, the genetic
drift and inbreeding potential of the two breeding schemes are
basically identical. In this scenario, the 4 fish breeding
population is as effective as the 100 fish population.
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