Pathways Student Conducts Spawning and
Recruitment Study in Restored Wetlands
BY RACHEL VAN DAM, GREEN BAY FWCO
Spring means the beginning of the busy field season at the Green Bay Fish and Wildlife Conservation Office (FWCO). The field season is proving to be especially busy for several staff that are collecting data for their master’s degree at University of Wisconsin-Green Bay. These two-year projects not only focus on issues of interest to the US Fish and Wildlife Service (Service), but also contribute to furthering the Service mission. One of the projects, conducted by Pathways student Rachel Van Dam, focuses on wetland restorations along the West shore of Green Bay. We are using northern pike (Esox lucius) as an indicator of success in restoring wetlands. The wetlands were constructed in areas of degraded or altered wetland habitat, with the intention of supporting spawning and recruitment of pike. This report details the methods and results of the study.
The project began in the spring of 2014 during the spawning run of the adult pike. To determine the success of these wetlands, fyke nets were set in each of three restored wetland areas to catch all incoming or outgoing adult pike. In 2015, a natural wetland site was also added to compare to the restored sites. The nets are checked daily. Each adult is tagged with a numbered, color-coded floy tag (pink for females, green for males) to determine entry and exit timing and whether the fish returns to one of the spawning wetlands the next year. Adults are also measured, and a fin clip is taken for genetic analysis. Within each wetland, the vegetation, water depth, and water temperature are characterized both across the wetland and at individual spots where adult pike are observed spawning. This will help to inform those constructing the wetland on areas where adult pike preferred, so similar areas can be included in future projects and possible unnecessary factors can be excluded.
After the eggs hatch, light traps are placed throughout the wetlands. These determine where young-of-year pike congregate and will inform future projects. Box traps are placed downstream of each wetland entrance to capture larval pike as they migrated out of the wetland. The traps are checked daily, with up to 30 larval pike measured at each site, and a total count is obtained. Ten percent of the larvae are collected for genetic analysis and will also be used to determine parentage information. Ultimately, one goal of this project is to determine how many fish are using the wetlands and whether recruitment is comparable to natural sites, which are being studied by others at the University. The other main goal is to provide useful information to those constructing the wetlands so future projects can include necessary elements but exclude anything deemed unnecessary. This will provide fish with more quality areas to spawn and will contribute to overall population recruitment of both northern pike and other species.
Other notable species have been seen using these wetlands to spawn, including banded killifish, bowfin, white sucker, shortnose gar, common carp, central mudminnow, sunfish species, and several minnow species, mostly shiners. This indicates that the restored wetlands benefit not only northern pike, but many other fish in the Green Bay system, contributing to the populations of the whole fishery.