Genetic differentiation of the three cod populations was measured
using the fixation index (FST) (Weir and Cockerham, 1984).
Two models
of Baltic population structure were tested: first assuming the existence
of 3 separate subpopulations and the second where eastern subpopulations
were grouped together.
In the first model variance amongst populations
was low (Va = −0.13%) whilst in the second dataset Va was
noticeably higher (Va = 5.49%).
The highest amount of variance occurred
within individuals (96.75% in 1st and 94.53% in 2nd dataset).
Variance amongst individuals within populations was very low(respectively
3.38% and −0.03%).