There’s always something to learn in the outdoors
BY DALE BOWMAN firstname.lastname@example.org July 6, 2013 12:38AM
Solomon David and Rachel Van Dam work a seine in a ditch off Green Bay as part of a study of migratory northern pike. | Dale Bowman~For Sun-Times Media
Updated: August 8, 2013 6:42AM
GREEN BAY, Wis. — Solomon David gave us a minnow net to scoop larvae northern pike from a trap in a ditch off a restoration area near Green Bay.
The only problem was, it was nearly impossible for Meg Matthews and me to see the roughly 1-inch slivers well enough to net them inside the wooden traps.
But it was neat to wade into the full experience of the journey young pike must survive to reach Green Bay from spawning areas far up streams and ditches in Brown County.
In May, I drove to the University of Wisconsin-Green Bay to observe a broad-based study on migratory northern pike in Green Bay. I waded ditches and wetlands with David, a postdoctoral research associate at the Shedd Aquarium; Patrick Forsythe, an assistant professor in natural and applied sciences at UWGB; Matthews, the manager of conservation communications for the Shedd; and Rachel Van Dam, a UWGB grad student.
Last week, I caught up with David to wrap up what was learned this spring in the ongoing study.
‘‘It was interesting verification of some fish making it out into the bay and the size of them,’’ he said.
Of the thousands that hatch and begin the journey toward the bay, at least some are making it. Data is being crunched now.
In mid-May, the ones David and Van Dam were measuring from the ditches were 1 to 11/2 inches. Making it from up the ditches to the bay is not so much a journey as running a gantlet of challenges. By last month, the biggest survivors to reach a wetland off the bay were roughly 51/2 inches.
Fluctuating water levels and water temperatures weren’t a big problem this spring. But there was still the ‘‘perch cloud’’ — yellow perch and other predators stacked below a culvert, waiting for the larvae to wash out, much like overeaters lining a dinner buffet.
In May, David and Van Dam netted that area to show what was in the ‘‘perch cloud.’’ Then we waded downstream along the path the small pike would take to a wetland off the bay. If pike reach that wetland by late spring, they would be relatively safe because most of the predators would have returned to the main bay by then.
All the same, David said, ‘‘It’s a treacherous life.’’
One of bigger questions being studied by the Shedd and UWGB is whether the restored ditches are a good thing overall or if they draw spawning pike into ditches, which fluctuate more in temperatures, more than to natural streams.
That’s one reason the study is ongoing and compiling data from several years.
One tangential benefit of the study shows the ‘‘multitude of species’’ (about 30) that use the ditches and channels. Included are four different darters, shortnose gar, bowfin, banded killifish (several dozen), stickleback and central mudminnow, an air-breather related to pike.
‘‘I can’t emphasize how much the biodiversity was surprising to me,’’ David said.
I was intrigued that once the pike had reached the wetland area on the edge of the bay, they were already gung-ho predators, preying on young-of-the-year perch.
There are many strands to this study.
There’s more to come, especially in regard to bigger conservation questions. Are the restored areas and ditches an economically viable thing overall? How fast do the young pike grow in different environments? What happens with other species in those restored areas as the years mount?