design: Genomic libraries were prepared following a typical ddRAD protocol using the SbfI-SphI enzyme pair, commonly used for fish species. Libraries were PCR-amplified with 19 cycles and a gel cut-window of 400-700 bp was used. Five multiplexed libraries were finally sequenced on an Illumina HiSeq 4000 platform (150 bp, paired-end) at the Norwegian Sequencing Center.