Data from: High synchrony in size at maturity of Atlantic salmon over a large geographical scale

Size at maturity is an important demographic characteristic due to its
strong effect on fecundity. Synchrony in size at maturity across
populations suggests similar environmental conditions, partly through
shared feeding grounds. We study synchrony in size at maturity over 30
years across 187 populations using data of about 200,000 individual
Atlantic salmon belonging to four geographic regions in Norway. Synchrony
was very high among the three southern regions, while the northernmost
region had more independent fluctuations. Synchrony among closely
separated populations was high, declined with distance, but was still
significant 1000 km apart. Fulton’s condition factor was consistently
larger in the North region, further emphasizing the difference between
this region and the three southern regions. The high synchrony reflects
that fish within each population have a wide oceanic distribution and
therefore, on average, experience a similar environment across
populations. Despite that, the northernmost populations forage more north
and east of the more southern populations. The high synchrony in size at
maturity will generate synchrony in egg deposition, with demographic
consequences on a broad geographic scale.