Dataset: Pool-seq data from wild populations of copepods in the Baltic Sea from May 2018 through August 2019

Sampling and analytical procedures:
Wild Eurytemora affinis populations were collected from eight locations in the Baltic Sea using bongo and WP2 nets with 100 micrometer (μm) mesh. Copepods were stored in RNAlater. Sampling locations spanned a range of mean annual salinities from low (~3 PSU) to higher (~19 PSU). From each population, individual copepods (ranging from 50 to 200 in number) were pooled and their DNA was extracted using the DNeasy Blood and Tissue Extraction kit (Qiagen, Inc.). Paired-end whole-genome sequencing libraries were prepared using the Illumina Nextera DNA kit (Illumina, Inc.) and sequenced on five lanes of an Illumina HiSeq 4000 sequencer at the University of Chicago Genomics Facility, generating an average of approximately 176 million paired-end (100 bp) reads per pool.