Reproductive contribution of lake sturgeon transferred upstream of dams on a Great Lakes tributary

Dam construction contributes to declines in the abundance and distribution of many fishes. Increasing connectivity through adult transfer can be demographically/genetically beneficial but assessing the effects resulting from transfer can be difficult if resident fish exist upstream. Genotypes of adult/larval lake sturgeon (Acipenser fulvescens) were used to quantify contributions to larval recruitment from adults transferred upstream of dams on the Menominee River, USA. We evaluated whether transfer timing, sex, and adult size were associated with the odds of reproduction. Elevator transfer operations in Fall 2019/2020, and Spring 2021 resulted in 152 male and 81 female lake sturgeon transferred upstream. In 2020 and 2021, 580 and 518 larvae were genotyped. 86% (201/233) of adults reproduced and 62.3% (684/1098) of offspring had transferred parents. 392 resident adults contributed to offspring production. Mixed matings accounted for 53% of offspring genotyped, increasing levels of offspring genetic diversity relative to offspring produced from resident-only matings. Transferring adults may be a viable restoration alternative for other iteroparous fish in river systems where connectivity to spawning areas has been impeded.

Methods
Adult lake sturgeon for upstream transfer were collected from the section of the Menominee River below Menominee Dam and were released above Park Mill Dam into USF (Fig. 1). Collection of larval sturgeon for parentage assignment occurred in the upper portion of USF, just below Grand Rapids Dam.Standard D-frame drift nets were used to collect larval lake sturgeon dispersing from spawning grounds in 2020 and 2021 (Smith and King 2005; Tucker et al. 2021). Genomic DNA was extracted from fin clips of all adult and larval tissue using the DNeasy Blood and Tissue kit (QIAGEN, Germantown, MD). DNA samples were quantified using a NanoDrop 1000 spectrophotometer (Nanodrop Technologies, Wilmington, DE) and diluted to 20 ng/µl for use in PCR reactions. Individuals were genotyped at 13 disomic microsatellite loci as described in Hunter et al. (2020) and Scribner et al. (2022).