Variable habitat use supports fine-scale population differentiation of a freshwater piscivore (northern pike, Esox lucius) along salinity gradients in brackish lagoons

The data in this dataset was collected by sampling otoliths and genetic samples from northern pike along environmental gradients in Baltic Sea brackish lagoons. Measurements of stable oxygen isotopes as thermal marker and strontium-calcium ratios as a saline marker were taken from the otoliths. The genetic samples wee whole genome sequenced and genotyped using a SNP panel of 33 diagnostic markers. Annual otolith increments, along with age information, were used to asssess growth performance at the individual level.