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Bryan Blawut, Richard D Zweifel, Joseph D Conroy, Saugeye (Sauger × Walleye) are naturally fertile and produce large quantities of gametes yielding viable larvae in fertilization experiments with congenerics, North American Journal of Fisheries Management, 2025;, vqaf023, https://doi.org/10.1093/najfmt/vqaf023
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ABSTRACT
Management agencies in the Midwestern USA stock saugeye (Sauger Sander canadensis × Walleye Sander vitreus) assuming that these hybrids are sterile. To date, few studies have directly evaluated whether saugeye can reproduce with parental species or other first-generation (F1) hybrids. One ex situ study reported that saugeye produced viable offspring with one parental species (i.e., are fertile). However, researchers used hormone induction, which undermines in situ fertility assumptions. Verifying the extent of natural saugeye fertility requires further research. Here, we sought to (1) determine whether saugeye produce gametes without hormone induction, (2) quantify gamete production, and (3) evaluate gamete viability (as hatching success) for all nine crosses (e.g., female × male: Walleye × Walleye, Sauger × Sauger, Walleye × Sauger, Sauger × Walleye, F1 × F1, Walleye × F1, F1 × Walleye, Sauger × F1, F1 × Sauger) among Sander spp. taxa (Walleye, Sauger, and saugeye).
We collected wild broodstock in March, maintained them in captivity, and collected gametes from individuals releasing gametes naturally (noninduced) or after hormone induction (induced, females only). We determined total gamete (eggs and sperm) production per individual and assessed gamete viability by evaluating egg hatching rates using all crosses.
We found that saugeye produced gametes without hormone induction. Fecundity estimates (eggs per kilogram body weight) did not differ between induced and noninduced saugeye, nor did it differ among taxa (about 55,000 eggs/kg). Sperm production (milt volume and total sperm) differed among taxa (Walleye > saugeye > Sauger), but all taxa produced high-quality sperm (motility > 60%). All crosses yielded viable larvae at hatching. We observed no differences in hatching among parental species (32%), F1 (24%), backcrossed (29%), or second-generation hybrid (41%) larvae.
Our results show that ex situ saugeye produce large quantities of gametes that result in viable larvae when crossed with both parental species and other F1 hybrids. Confirming in situ fertility requires further larval viability and population genetics studies. Fisheries managers providing recreational fishing opportunities by stocking saugeye should consider possible introgression.
Lay Summary
Management agencies suspect saugeye are fertile, but few studies exist despite the potential impact on Sander spp. genetic integrity. Here we report that saugeye can spawn naturally, yield large quantities of gametes, and produce viable 4-d-old larvae when crossed with Walleye, Sauger, and other saugeye.
