Wisconsin research takes a closer look at sturgeon spawn

Stevens Point, Wis. — As spring begins, warming temperatures and vibrant colors will return to the landscape and once again set the scene for the season’s main event in Wisconsin’s Winnebago system – the lake sturgeon spawning run through the Fox River and Wolf River drainages to spawn at over 70 possible sites.

These fish can move quickly and capture the public eye as they gather by the hundreds along the riverbank at sites such as Bamboo Bend in Shiocton, Sturgeon Trail in New London, and Sturgeon Park in Shawano. The proximity of these fish provides an opportunity for the Wisconsin Department of Natural Resources (DNR) to tag adult lake sturgeon as part of the mark-recapture population estimate used to set harvest caps for the spear fishery.

To maximize tagging efforts, the DNR often prioritizes spawning sites that host large groups of lake sturgeon. However, this prioritization limits the information on lake sturgeon throughout the remainder of the system that’s not regularly sampled. With this in mind, the DNR worked with UW-Stevens Point to develop a research project examining the timing and extent of spawning-site use by lake sturgeon throughout the Wolf River drainage.

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Information from this study will be used to align DNR sampling schedules with patterns in spawning site use to help maximize lake sturgeon tagging numbers while ensuring a good distribution of tags at spawning sites throughout the system. This study will also inform the DNR about the success of reconstructed habitat sites, helping make decisions about future site selections.

To implement this project, the DNR has been funding a graduate research project through the Wisconsin Cooperative Fishery Research Unit at UW-Stevens Point. Graduate student Sam Embersits has spent the last two years tracking lake sturgeon spawning site use across natural and reconstructed sites in the Wolf River drainage.

Embersits tracked lake sturgeon spawning at 15 private and public sites across the Wolf River system. This included the larger sites regularly sampled, as well as smaller sites not often frequented by the DNR due to time constraints. To analyze spawning site use and success, she counted spawning fish, collected eggs and sorted them based on quality (live or dead), and collected larvae.

Embersits found that there were no specific patterns in the timing of site use during peak spawning temperatures during this study period. She also found that the proportion of live eggs to total eggs (percent live) varied across spawning sites, but with no correlation to the number of sturgeon using the site, nor to total egg abundance at the site.

From these results, researchers can say that if spawning site patterns are occurring, they may have to look across more years to see whether these patterns occur under specific environmental conditions or differ under different environmental conditions. In addition, researchers can say that during these years, the habitat locations examine seem to be able to adequately support the number of sturgeon using them to spawn.

Embersits also has learned at least one site not routinely sampled by the DNR was found to have high use by lake sturgeon. This site is a good candidate for the DNR to try and sample regularly, as well as maintain habitat in the future.

Embersits’s research also included finding unique ways to help gather information during the short spawning duration. To continue support for the DNR beyond her research project, Embersits trained a small group of volunteers, with the help of Sturgeon Guard, to track spawning-site use in the coming years. This group will help maximize the impact of the DNR’s spring sampling efforts by providing data on spawning activity throughout the system.

“This will provide the DNR crews with real-time information on where there are spawning lake sturgeon and reduce the amount of time crews will have to spend looking for spawning activity,” Embersits said.

This also will provide additional information on spawning-site use by lake sturgeon when sampling crews are unable to respond while sturgeon are present. Both will help the DNR sample more efficiently and create a more complete record of lake sturgeon use throughout the entire Wolf River drainage.