This week, Crossroads at Big Creek hosts the final program in the Fish Tales Lecture Series, featuring one of our favorite presenters, Dr. Dan Isermann. His topic — “Movement and Mixing of Smallmouth Bass Spawning Groups in Green Bay” — centers on a fish perfectly designed for our waters.

Smallmouth bass flourish in the rocky habitat that defines much of Green Bay. They prefer reefs and shoals of limestone — technically, dolostone — along with glacial rock piles, deep breaks, and clear water for spawning. The Niagara Escarpment along the western side of the Door Peninsula provides exactly that combination. It’s no wonder Green Bay has become nationally known for its bass fishery.

Many people assume fish simply scatter eggs and swim away — and usually, they are correct. The majority of egg-laying species (an estimated 79%) do not guard their young.

But smallmouth bass tell a different fish tale.

In this species, the male does the heavy lifting. He selects a nest site and fans a shallow depression in gravel or firm sand, typically in a location protected from strong currents and wave action. A female joins him and may lay between 2,000 and 20,000 eggs, depending on her size.

After fertilization, she leaves. He stays.

And that’s when the real work begins.

For days — and sometimes weeks — he eats very little and often loses weight. His immune function can be suppressed, making him more vulnerable to disease. He constantly fans the nest to keep sediment from smothering the eggs and to increase oxygen flow.

Most importantly, he defends the nest from predators that would quickly devour unguarded eggs or fry. But every chase is a risk. If he strays too far, the nest may be raided. If he is too bold, he could become prey himself.

After the eggs hatch, the fry — often described as a wriggling mass of tiny fish — remain near the nest for one to three weeks, depending on water temperature. During that entire time, the male continues guarding them until they disperse.

And this is where science meets real-world questions.

Green Bay is a popular spring destination for anglers, especially during the bass pre-spawn and spawn. Catch-and-release is common and widely practiced.

But what happens if a guarding male is caught while his eggs or fry still depend on him? If he is released some distance away, will he return? How long does it take? And what happens to the nest while he’s gone?

Using acoustic tagging technology, Dr. Isermann and his graduate students have tracked smallmouth bass implanted with tiny transmitters. By following displaced fish released at various sites, their research sheds light on how often males attempt to return, how far they travel, whether spawning groups mix across different parts of the bay, and what temporary nest abandonment might mean for reproductive success.

This work contributes to ongoing discussions about catch-and-release practices and seasonal regulations during the spawning period in one of the Midwest’s premier bass fisheries.

Dr. Isermann is Unit Leader of the U.S. Geological Survey’s Wisconsin Cooperative Fishery Research Unit, housed at the University of Wisconsin–Stevens Point.

If you care about Green Bay fisheries, about good science, or are simply curious about the remarkable dedication of a two- to four-pound father fish, this is a program you won’t want to miss.

Other programs this week include Monday Movie Matinee, Wandering Wednesday, and Nature Investigators.

The Collins Learning Center is open 9:30 a.m.–3:30 p.m. weekdays and from 9:30 a.m. to noon on Saturday. Trails are open all day, every day, free of charge. Conditions permitting, skiing and snowshoeing may be available. Check our website for open hours and current trail conditions.

Thursday, March 12

3:30–4:30 p.m. Nature Investigators: Wildlife Tracks

Geared for school-age kids, all are invited to dive into weekly, hands-on nature adventures. Each session explores a new environmental mystery — this week, participants will examine the feet of the creatures in our Wildlife Exhibit and determine how these animals move through their habitats. Free and open to the public. Meet at the Collins Learning Center, Crossroads, 2041 Michigan Street, Sturgeon Bay.

7:00 p.m. Fish Tales: Movement and Mixing of Smallmouth Bass Spawning Groups in Green Bay

Speaker Dr. Dan Isermann, Unit Leader, U.S. Geological Survey’s Wisconsin Cooperative Fishery Research Unit, UW–Stevens Point, will discuss the spawning behavior and movement of smallmouth bass. Free and open to the public. Meet at the Collins Learning Center, Crossroads, 2041 Michigan Street, Sturgeon Bay.

Monday, March 16

1:30 p.m. Monday Movie Matinee – “An Original DUCKumentary”

Masters of the water and air, ducks have conquered the globe. From deft dabblers to great divers, these are among the animal kingdom’s ultimate athletes. Take a fascinating look at ducks. Free and open to the public. Meet at the Collins Learning Center, Crossroads, 2041 Michigan Street, Sturgeon Bay.

Tuesday, March 17

6:30 p.m. Door County Beekeepers Club: Swarms

The Door County Beekeepers Club encourages community members to attend this monthly program to learn more about swarms. Free and open to the public. Meet at the Collins Learning Center, Crossroads, 2041 Michigan Street, Sturgeon Bay.

Wednesday, March 18

1:30 p.m. Wandering Wednesday

Join a naturalist on a guided hike through the trails of Crossroads. Free and open to the public. Meet at the Collins Learning Center, Crossroads, 2041 Michigan Street, Sturgeon Bay.