Data from: Spontaneous hybridization and introgression between walleye (Sander vitreus) and sauger (S. canadensis) in two large reservoirs: insights from genotyping-by-sequencing

Anthropogenic activities may facilitate undesirable hybridization and
genomic introgression between fish species. Walleye (Sander vitreus) and
sauger (Sander canadensis) are economically valuable freshwater species
that can spontaneously hybridize in areas of sympatry. Levels of genomic
introgression between walleye and sauger may be increased by modifications
to waterbodies (e.g., reservoir development) and inadvertent propagation
of hybrids in stocking programs. We used genotyping by sequencing (GBS) to
examine 217 fish from two large reservoirs with mixed populations of
walleye and sauger in Saskatchewan, Canada (Lake Diefenbaker, Tobin Lake).
Analyses with 20,038 (r90) and 478 (r100) SNPs clearly resolved walleye
and sauger, and classified hybrids with high confidence. F1, F2, and
multi-generation hybrids were detected in Lake Diefenbaker, indicating
potentially high levels of genomic introgression. In contrast, only F1
hybrids were detected in Tobin Lake. Field classification of fish was
unreliable; 7% of fish were misidentified based on broad species
categories. Important for activities such as brood stock selection, 12/173
(7%) fish field-identified as pure walleye, and 1/24 (4%) identified as
pure sauger were actually hybrids. In addition, 2/15 (13%)
field-identified hybrids were actually pure walleye or sauger. We conclude
that hybridization and introgression are occurring in Saskatchewan
reservoirs, and that caution is warranted when using these populations in
stocking programs. GBS offers a powerful and flexible tool for examining
hybridization without pre-identification of informative loci, eliminating
some of the key challenges associated with other marker types.