May 10, 2014

Walleye Movement in the Lake Winnebago System (2011-2013)

By: Ryan Koenigs – Senior Fisheries Biologist with the Wisconsin DNR in Oshkosh

The Lake Winnebago system is home to a nationally recognized walleye fishery that receives substantial angler effort. The angling public is also heavily engaged in the management program and collaboratively works with DNR fisheries staff to promote, research, and effectively manage the fishery. As part of this collaborative effort, DNR fisheries staff and local stakeholders recently conducted a sonic telemetry study to learn more about the movement of adult walleye within the system.

The project involved the surgical implantation of 100 sonic tags into adult walleye captured during spawning assessments conducted throughout the Lake Winnebago system. Unfortunately, a $320 cost was associated with each tag, meaning the project cost $32,000. Local fishing clubs and conservation organizations stepped up to the plate and donated the funds to support the project. The tags carried a 900 day battery life and transmitted a unique pinging sequence 24 hours/day, 7 days/week. Thirty-five stationary receivers dispersed throughout the system, mostly on bridge crossings, listened for the tags and the date, time, and tag number was recorded every time a tagged fish was within detection range of a receiver. This technology allowed us to monitor the coarse movement patterns of adult walleye, while answering many anglers’ questions about fish movement in the process.

All 100 tags were implanted into walleye during 2011 spawning assessments, with 60 fish being tagged from the Wolf River, 30 fish from the upper Fox River, and 10 fish from Lake Winnebago (tags were evenly split between males and females at each location). The battery life of the tags allowed us to monitor fish movement from April 2011-October 2013.    

Many interesting and distinct trends were observed during the course of the study. For example, male walleye occupied the Wolf and upper Fox Rivers for a considerable longer period of time during spring spawning periods. This should come as no surprise due to the spawning nature of the fish; males remain on spawning grounds until all spawning has concluded, while females typically start their downstream descent shortly after spawning out. This behavior explains why the spring fishery on the rivers is dominated by males, simply put, they are susceptible to that fishery for an extended period of time compared to females.

It was also interesting to see where the fish tagged on the upper Fox River spawned following tagging. Six of the 15 females tagged at Eureka moved upstream of the Princeton Dam and spawned in Lake Puckaway in 2011, while none of the males exhibited this movement. These results clearly demonstrate that fish are able to move upstream of the Princeton Dam in high water years and that fish readily move between Lake Puckaway and the Lake Winnebago System. Fish tagged on the upper Fox River also showed poor river fidelity across spawning runs. Only one of the 30 fish tagged on the Fox River spawned in the Wolf River in 2011, but river system straying was more prevalent in 2012 and 2013. In fact, of the 12 females that were still alive in 2012, 3 spawned in the Wolf River and one spawned in the Embarrass River. We even observed a fish that spawned in three separate rivers (Fox 2011, Embarrass in 2012, and the Wolf in 2013) during the three year study. In comparison, no river straying was observed in fish initially tagged on the Wolf River.

Another surprising result was the portion of fish that remained in the Upriver Lakes (Poygan, Winneconne, and Butte des Morts) throughout the majority of the year. Females had a higher residency in the Upriver Lakes than males and fish marked on the Wolf River demonstrated this movement more than those marked on the upper Fox River. Although some fish remained in the Upriver Lakes throughout the summer, the majority did move downstream into Lake Winnebago. Most of the Wolf River spawners entered Lake Winnebago during early to mid-May, while the majority of fish that spawned in the Fox River entered Lake Winnebago in mid to late April. This disparity is likely due to where the rivers drain, as fish from the Wolf River need to move through all three Upriver Lakes to reach Lake Winnebago, whereas fish from the Fox River only need to move through one lake.

Regardless of when fish reach Lake Winnebago, telemetry results clearly demonstrate a large upstream movement of adult fish in late-fall. More specifically, fish from both the upper Fox and Wolf River are moving from Lake Winnebago into the Upriver Lakes to overwinter. This movement, occurring mostly between mid-October and December, occurred in both 2011 and 2012. These results address questions about the ice fishing on Lake Winnebago. Walleye, especially larger walleye, do not show up in the harvest of most ice fishermen. As the telemetry data indicate, this is a product of not having large numbers of adult walleye in Lake Winnebago during that time.

All of the results and trends discussed thus far have described movement of fish marked on the upper Fox and Wolf Rivers. As described earlier, we also implanted tags into 10 fish captured in Lake Winnebago, mostly from west shore reefs just south of the mouth of the Fox River in Oshkosh. Many of the fish were not contacted at any of our receivers meaning that they either never left Lake Winnebago during the study period or they died of either harvest or natural causes. Overall, the results from these fish were not definitive and thus not included in the report.

Unfortunately, quite a few of the tagged fish succumbed to mortality, fishing and natural, during the course of the study. Age and growth data collected by DNR fisheries staff indicate that 30-35% of the adult walleye population within the system succumbs to mortality in an average year. Therefore, we were anticipating that a high percentage of tagged fish would no longer be living when the tags expired.

Even with the mortalities, this was a very beneficial study to both our DNR staff and to the general angling public. Anglers are very interested in how fish move throughout the system and will look to apply these results to their fishing practices in years ahead. Results that would best translate to more fish in the boat would be to know where fish are during different periods of the year. Granted the timing of movements will be variable from year to year depending on weather trends, but there are general trends. For example, adult fish are concentrated in the rivers through late April – early May before entering the Upriver Lakes, meaning the rivers would be the best place to fish early open water. The Upriver Lakes hold adult fish throughout most of the year, but the highest concentration of fish are present during the first couple of weeks in May. The biggest movement of adult fish into Lake Winnebago occurs during the first few weeks in May making early season open water fishing on Wisconsin’s largest inland lake tough if strong year classes of immature fish are not present in the lake. Either way, the Lake Winnebago system is a very productive water body with an exceptional walleye fishery, so get out there and enjoy it! 

This was a condensed version of a more in-depth report, so feel free to contact me via email Ryan.koenigs@wisconsin.gov for the full report.