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At 41.5% of it’s total area, the state of Michigan has a greater portion of it’s area composed of water than any other state in the union. While the same can be said of any other area of the world, the story of life in Michigan is simply incomplete without talking about it’s more aquatic side. According to the Native Fish Coalition, “Michigan is home to over 120 species of native fish across more than 20 families.”

With that in mind, it should go without saying that water activities are a common way for people to enjoy the great outdoors. One particularly popular way for people to enjoy Michigan’s various waterways is through recreational fishing. According to the Michigan Department of Natural Resources (DNR) fisheries division 2025 annual report, 1.2 million people carry fishing licenses in the state. One of the main tasks of the DNR is to help support Michigan fisheries to ensure that they continue to thrive for future generations.

One way that the DNR does this is through their fish stocking program, in which the state gathers fish eggs from the wild, hatch and raise a number of them for a time in special facilities, and then re-release them to help protect Michigan fisheries. In order to better understand this system, we’ll follow the path a specific set of fish, in this case Walleye (Sander vitreus), through the Michigan DNR fish stocking system.

To start our expedition, we find ourselves in the shadow of the historic Croton Dam. At a small boat launch hidden from the main road by thick forests and hills, DNR biologists and technicians prepare to collect fish for harvesting. By the time I arrived, some fish had already been collected and sorted by sex, awaiting processing in large nets that sat at the edge of the water at the boat launch.

When the boat sent out for fish collection returned, one would likely first notice the strange thin tendrils hanging from the boat, hanging out into the water like long fingers. These are the electro traps used to collect the fish. Rather than relying on blindly angling for their target species, DNR biologists instead send a weak electric current into the river, temporarily stunning the fish and causing them to float to the surface. According to Mark Tonello, a biologist with the Michigan DNR, “Electrofishing is a mostly non-lethal method of collecting fish. There is the occasional mortality, but the vast

majority of fish are released unharmed and they recover just fine.” From here, the fish are collected and put into the boat’s collection bin. Upon return, the fish are sorted into each sex’s net. Females are farther sorted between three categories; green, which are not yet ready for egg collection, ripe, which are females ready for egg collection, and spent, which are females that have already laid their eggs.

While, for the most part, only ripe females are held for egg collection, a few green females are kept and put into their own net. These fish are used as ambassadors for the species, with onlookers from the general public being invited to hold them and take pictures. The first day was a beautiful, sunny April morning, bring out a variety of local anglers to watch the beginning of their potential future quarry.

When staff from the fish hatchery arrive, egg collection begins in earnest. I had to observe this process on a different day of the egg collection process, under a gray rainy sky. While the weather certainly deterred the crowd from the first day, it was a blessing for walleye and those searching for them. Adapted for low light conditions, these fish love the overcast conditions. One of the workers for the egg collection mentioned that they were having notably high fish collection rates on that day.

After backing the large trailer used to transport eggs into the boat ramp and setting up the egg collection equipment, technicians sat down and had ripe females handed to them. Stationed at specialized stools with built in slots for collection dishes, the technicians carefully massaged the fish in a way to get them to release their eggs. Males are somewhat similar, being placed in a bucket while waiting for their malt to be collected. After processing, the Walleye have a portion of their fin clipped in order to genetically track the fish and their descendants. According to Matthew Hughes, general manager of the Wolf Lake State Fish Hatchery who was present to assist with egg collection, this is a relatively new system. “We used to mark all of our fry with a chemical known as oxytetracycline. The fish would have to be at least three days old before they start to develop bony structures, like vertebrae, spines, whatnot. So we would soak them in a chemical and it would get taken up into their bony structures. Down the road if it was caught in a survey, we could take a spine sample and that spine sample would glow under black light. Therefore, you would know that it was a hatchery fish.”

The collected eggs and malt are then mixed together in 5 gallon buckets with clay. Notably, the preferred tool for this job are bird feathers, due to the fact that they’re gentler on the eggs. Now fertilized, the eggs are dumped into a net that sat in the river. Sheltered behind a wood board and held in place by poles driven into the riverbed, the net allows the eggs to soak. This results in the eggs becoming “water hardened”, helping them withstand the trip to the egg hatchery.

Once the eggs are collected and prepped, the fisheries staff will put them into the transport trailer and ship them to the fish hatchery. Specifically, the Walleye will be taken to either the Platte River fish hatchery or the Wolf Lake fish hatchery. We will be following them to the latter.

Located in Mattawan, Michigan, the Wolf Lake State Fish Hatchery is a facility dedicated to incubating the collected fish eggs and holding the resulting young until they can be moved to fish raising ponds. One of six such facilities, Wolf Lake raises four different species of fish for the state’s fish hatchery system, including the aforementioned walleye. Alongside them, Wolf Lake fish hatchery raises steelhead, chinook salmon, and great lakes muskellunge.

When arriving to the facility, the eggs are counted. Due to the shear amount of eggs, with the final fish fry count numbering in the millions, counts are conducted indirectly by taking samples. To start, hatchery workers will put 5 milliliters of water in a specialized measuring device. These are standardized across the Michigan DNR fisheries system so as to ensure separate fish hatcheries will arrive to similar measurements. Three milliliters of eggs will be strained from the water and then put into the device, which uses water displacement to measure the volume of eggs. These eggs will then be manually counted, with the density then elaborated to determine the overall number of eggs.

The fish eggs are kept in large, clear, cylindrical containers referred to as jars. Dozens of these jars are held in fish batteries and held in custom rooms for the job of holding the eggs and facilitating their care while they develop. Cacophonous from the constant sound of running water and wet from the various pipes transporting and releasing water, I was allowed to visit this room with Matthew Hughes.

Immediately noticeable is the difference in colors between the eggs, with some being a light cream color, while others are a dark, almost black, color. This helps to establish what stage of development the egg is in. When first arriving at the hatchery, the eggs are the more cream color. At this stage, the eggs have to rapidly be set up in the fish batteries. After the first few hours, the eggs cannot be touched. After some time, the developing fish grow eyes, giving the eggs the dark color mentioned before. One will notice, however, that some light colored eggs will remain through out this stage. These are dead eggs that will be vacuumed out of the jars on a daily basis.

More goes into the care of the eggs then just vacuuming, however. When the eggs first come into the facility, the water flow through the jar has to be very low, almost to the point of nonexistent. As the eggs develop, the hatchery can increase the flow in order to keep the water oxygenated.

The hatchery has refined the care of fish eggs to the point of having a way of precisely measuring the amount of time it will take for an egg to develop and hatch. According to Matthew Hughes, “Our water temperature never changes, it’s always at 52 degrees farenheit (10 degrees celcius). Each day you’re going to add your temperature together”. By this, Hughes is referring to a measurement known as temperature units, which is each day’s temperature added together. For example, if one day the eggs are held at 10 degrees celcius and the next they’re 12 degrees, the eggs would have 22 temperature units. “We know, from over the years of raising Walleye, how many temperature units when Walleye are going to develop eyes, when they're gonna hatch, when they’re gonna absorb their egg sack. It’s all very measurable because our water temperature stays constant.”

After the eggs hatch, the fry will swim to the top of the jars and into out into the central outflow canal of the fish battery. Hughes describes how the hatchery sets up pipes to funnel them into large circular holding tanks. From here, the small fry will be held in long, concrete fish tanks while awaiting to either be released into the wild or to fish rearing ponds around the state in order to farther grow.

The exact end point for the fish is decided by the state’s biologists. An individual biologist is tasked with analyzing a specific geographic area, usually a watershed, to determine how to best manage fish populations. Using collected data, the biologist will produce a “prescription” for the body of water which dictates if fish would be stocked and at what size. According to Matthew Hughes, a major portion of figuring out what a water body’s prescription should be involves trial and error, with the DNR initially starting with newly hatched fry and gradually moving up to larger fingerlings. Younger fish are typically preferred due to the added cost of raising young fish, particularly in feeding them.

As mentioned, this process is an important part of Michigan’s recreational fisheries. Financially, recreational fishing in Michigan brings in about $2 billion annually, a large portion of which originates from the tourism revolving around said fishing. Another major benefit of this recreational fishing comes from the end product of this activity, fresh fish.

According to Daniel O’Keefe from the Michigan Sea Grant when talking about the food yield of a night of salmon fishing, “Before being cleaned, the total weight of Chinook salmon caught was 61 pounds. Fillet yield for Chinook salmon is 0.55, which means that I harvested roughly 35.55 pounds of fillets that evening. If you were to buy Chinook salmon harvested from the Great Lakes, you would pay $18 per pound through one of the few online retailers that offers the option.” Later, O’Keefe describes his findings that the overall economic value from the food provided by recreational fishing in Michigan to be about $40 million.

Recreational fishing helps taps into one factor of the natural world that’s often overlooked; it’s impact on local culture. Rather it be from the types of clothes people wear to the types of materials available locally, nature has a subtle yet omnipresent effect on people.

Recreational fishing allows people to source food from local, native species as opposed to fish shipped from 100s of miles away. Walleye, for example, are a culturally relevant part of Midwestern cuisine.

Fishing is a common childhood experience for Michiganders. The DNR even recognizes this by allowing children 16 and under to obtain fishing licenses. The DNR helps play a vital role in ensuring that the fish that help make Michigan waters a richer, more interesting place.

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I would like to give a special thanks to Mark Tonello, Sarah Carlson, and Matthew Hughes for their help in writing this article. I would also like to wish those reading this a happy (slightly late) 250th Independence Day!