Data from: Geographic variation in age structure and longevity in the nine-spined stickleback (Pungitius pungitius)

Variation in age and size of mature nine-spined sticklebacks (Pungitius
pungitius) within and among 16 Fennoscandian populations were assessed
using skeletochronology. The average age of individuals in a given
population varied from 1.7 to 4.7 years. Fish from pond populations were
on average older than those from lake and marine populations, and females
tended to be older than males. Reproduction in marine and lake populations
commenced typically at an age of two years, whereas that in ponds at an
age of three years. The maximum life span of the fish varied from 3 to 7
years. Mean body size within and among populations increased with
increasing age, but the habitat and population differences in body size
persisted even after accounting for variation in population age (and sex)
structure. Hence, the population differences in mean body size are not
explainable by age differences alone. As such, much of the pronounced
intraspecific variation in population age structure can be attributed to
delayed maturation and extended longevity of the pond fish. The results
are contrasted and discussed in the context of similar data from the
three-spined stickleback (Gasterosteus aculeatus) occupying the same
geographic area.