Male pumpkinseed, bluegill and largemouth bass at Nature Boardwalk at Lincoln Park Zoo are busy these days. At many locations around the pond, you can look down from the boardwalk and see these fish hard at work making, maintaining and defending their nests.
The nests look like round craters in the pond’s sandy substrate. In the most desirable sections of the pond, you can see many nests clustered together, seemingly crammed as tightly as possible. This produces the honeycombed pattern seen above.
To make these nests, the fish fan out an area using their fins. Once the nest is complete, defending it becomes a full time job. Males chase off intruders as they wait for a female to come along. (Bluegill males are more active in finding their mates—they grunt to gain a female’s attention!)
Pumpkinseed mating at a nest site. You can identify them by the red spot on the opercular flap (the fish's "ear"). Photo by Joel Pond.
After selecting a partner, the female swims in circles with the male at the nest. She then releases eggs, which are fertilized by the male.
At this point, the mother’s work is done. In these species, only the males take an active role in parenting. Eggs develop in the nest under the watchful eye of the father. He uses his fins to fan the eggs, keeping the nest clean and oxygenated as the young develop.
Once the young have hatched, the father continues to guard the baby fish (called “fry”) until they’re big enough to fend for themselves. Keep an eye out for these tiny fish swimming through the shallows at Nature Boardwalk next time you visit!