INTERPOPULATION VARIATION IN MALE PARR MATURATION OF ANADROMOUS BROWN TROUT (SALMO-TRUTTA) IN NORWAY

For anadromous brown trout in 9 Norwegian rivers, mean age at maturity increased from 1.5 yr in southern populations to 5.2 yr in northern populations, but the latitudinal correlation was not significant. Mean age of male parr at maturity was negatively correlated with mean total length of 0- and 1-yr-old parr. The proportion of mature male parr varied between 0.06-0.6 among populations, and was positively correlated with mean total length of 0- and 1-year-old parr. The proportion of mature male parr decreased significantly with increasing mean smolt age of males. In populations with relatively poor growth in fresh water (high smolt age) males mainly spawn as sea-run migrants, whereas in populations with relatively good growth in fresh water the mature male parr potentially contribute twice to the genetic makeup of the population, further increasing the effective population size. -Authors