Smallmouth bass and their role in the Huron River ecosystem
Have you ever wondered what they’re fishing for in the river? While there are a number of sportfish that make the Huron River and its lakes and tributaries home, the most popular catch in the river is the diminutively named Smallmouth bass (Micropterus dolomieu). In fact, if you ever watch a fishing competition, they are usually going after “smallies” as they are affectionately called, since these bass are known to be some of the most aggressive hunters in freshwater, and the most fun to catch!
A small bit of life history
Smallmouth bass are in the sunfish family along with smaller bluegills, crappie and rock bass, and the similarly sized largemouth. The main observable distinction between small and largemouth bass is the length of their upper “lip.” A smallie’s lip does not extend beyond its eye, while a largemouth’s lip extends well beyond. Smallies are native to the Great Lakes and Mississippi basins but have been introduced all over the country and are considered invasive in some western rivers.
Smallmouth reproduce or spawn in the Spring (roughly May 15 to June 15 in the Huron River) by making nests of small gravel in areas protected from fast flows by logs, rocks, vegetation or other barriers. The male builds a nest by sweeping his fins and attracts or drives a female to it. Females may lay eggs in multiple nests. The nests are constructed such that the river flows over the fertilized eggs, keeping them oxygenated, but not washing them away. The hatched fry stay in or near the nest until they are strong enough to venture out and feed on water fleas and other small organisms. The father guards the nest and stays with the fry until they start hunting on their own. Adult smallmouth are at the top of the aquatic food web in the river, hunting and consuming a wide variety of smaller fish, amphibians, insects and whatever else they can get their small mouths around, in turn keeping those populations healthy. The smallies themselves are eaten by riparian predators like raptors, heron, and mink.
Where to find smallmouth bass
While sometimes referred to as a warm water fish, smallmouth bass prefer cool water in the optimal range of 65 to 75 degrees Fahrenheit (°F). HRWC temperature studies show that this is the normal Huron River temperature range, except during the hottest summer days and in impoundments. Warmer water temperatures result in less dissolved oxygen in the water, which the fish need to live. When temperatures get above 80 degrees, the fish will slow down, reduce feeding and seek cooler areas.
Smallies love their cover. They are most commonly found around rocky and gravely substrate, near boulders, submerged logs and tree stumps that give them places to hide. The natural sections of the Huron River have much of this desired substrate in abundance. Smallies are less likely to be found near beds of aquatic vegetation.
Smallmouth bass are sensitive to excess sedimentation in water, as well as pollutants that are attached to the sediment, like pesticides and herbicides. Sediment can cover their gravely habitat and spawning grounds, while the chemicals interfere with reproductive and immune systems. Adult smallies are strong swimmers and can tolerate rapid flows. Eggs, small fry and fingerlings need to stay near nesting sites in waters that keep below 1 foot per second.
How are smallies doing?
Generally, smallmouth bass should thrive in the Huron River. They have ample habitat and the typical river conditions suit them. Past fish surveys have counted over 1000 smallmouth in some electroshocking samples at some sites. The Huron River is also home to the only known, year-round catch-and-release protection for smallmouth, covering the river section from Mast Road to Delhi Road. There have been observations from anglers recently that there may be a greater number of larger smallmouth individuals due to fish consumption restrictions on the river (consumption is not advised on the entire length of the river currently due to PFAS contamination), but sampling has yet to verify these anecdotal reports. On the other hand, the sediment plume that followed the Mill Creek dam removal may have covered significant habitat and recent erratic flows also likely impact spawning areas.
This year and next, thanks to a grant from the National Science Foundation, HRWC is partnering with the Digital Water Lab at the University of Michigan on a new project. The purpose of the project is to study the effects of changing flows on smallmouth nesting and develop a forecasting model to help dam operators plan gate changes and other management activities. All this effort is being done to protect nesting habitat for these important freshwater predators.
— Ric Lawson
This blog post is also published in the Huron River Report, Summer 2025.