Michigan Trout Unlimited
24
by Dr. Karen Murchie, Director of Freshwater Research, Shedd Aquarium Dr. Pete McIntyre, Associate Professor, Cornell University
Summer 2022
Dubbed the “wildebeests of the Great Lakes,” suckers are the most abundant migratory fishes in the region and are familiar to every trout angler. In the spring, these animals make incredible migrations from the Great Lakes into tributaries of all sizes to spawn. Typically, 2-3 male suckers gather around a ripe female, and in the act of spawning, they all vibrate intensely, releasing a cloud of milt and eggs. Some fertilized eggs stick to rocks while others drift downstream to settle in sandy ridges with sticks and leaf debris, or they become food for many other species. There is no mistaking when suckers are present to spawn because their numbers can often turn a tributary into a symphony of splashing. These annual and extraordinary events not only sustain sucker populations but also support trout in many ways. Sucker nutrients feed aquatic insects, which feed trout. As suckers spawn, nutrients like nitrogen and phosphorus are released into tributaries from eggs, milt, and excretory products. The spring timing of these nutrient pulses is akin to the first meal after long winter hibernation. This nutrient pulse jumpstarts the food web, resulting in increased algal growth and larger caddisfly larva for trout to eat. Suckers basically supersize the food options for trout, and who doesn’t love a free upgrade!?! More caloric content per bite is a win for any fish and can add up to an even bigger catch on the end of a line. Sucker eggs are eaten by trout. Speaking of caloric content, there is no bigger bang per bite than a nutrient-dense fish egg. Fish eggs are designed to supply nutrients to developing fry, so when fish directly consume eggs, they consume a concentrated packet of fatty acids and other goodies. Indeed, many fishers are aware of trout species that take advantage of the egg buffet—steelhead, brown trout, and brook trout—and anglers often converge on the Muskegon and Manistee Rivers to fish trout that have been gorging on sucker eggs. The number of eggs a female sucker carries will depend on the species and size. In the Great Lakes literature, the range for white suckers is 14,000 to 139,000 eggs. In a tributary of Lake Superior, where over 80,000 white and longnose suckers were counted, researchers estimated that over 12,000 pounds of sucker eggs were deposited. Since sucker eggs are not spawned over a redd, and because sucker eggs are relatively small, they are an easy target for predation. Between the egg-supplied fuel, coupled with supersized aquatic insect larvae, many stream-resident brook trout in Michigan likely have their annual energy budget fueled by suckers. Suckers are important forage for many recreational fish species. It is no coincidence that several fish species like brown bullhead, rock bass, pumpkinseed, smallmouth bass, and yellow perch congregate at the mouths of tributaries while the fry of suckers are making their journey out to the lakes. These species are cued to the seasonal timing of these swimming smorgasbords.
Larger suckers are also important forage for pike, muskellunge, walleye, burbot, and a variety of birds, including eagles and ospreys. Undoubtedly, predation on suckers redirects predation pressure from salmonids, so again, if you love trout, thank a sucker. Say goodbye to trash-talk and hello to sucker advocacy. Given the amazing ecological services suckers provide, you may wonder why suckers have been called trash fish and why they have received far less love. When was the last time you found a depiction of a sucker on a hat or t-shirt? A lot truly has to do with our subjective value placement on which species we deem important for recreation, food, and esthetics. Suckers are also plagued by a perception that they are detrimental to many sportfish because of egg predation and competition for resources (food and habitat). These myths are increasingly being debunked as more studies demonstrate that even when predation or resource competition occurs, these are not usually the reason for sportfish declines. Longer-term evaluation of sucker removal projects in Michigan lakes has also failed to demonstrate clear benefits to sportfish. On the contrary, relatively recent science on suckers demonstrates the immense value these fish convey to other fish and the broader ecosystem. Their influence and importance are beginning to come to light but are often overshadowed by species targeted by recreational anglers. Imagine an awards show that only presented awards to the best actors and never gave a nod of importance to supporting roles. It is definitely time to shine a spotlight on all native fishes, including suckers, that contribute enormous value to the incredible $7 billion per year fishery in our Great Lakes region. Suckers for suckers. You can contribute to sucker research by documenting when and where you see suckers spawning in tributaries and when and where you see suckers outside of their spawning season. This can be done using Shedd Aquarium’s Great Lakes Fish Finder application—a project nested under i-Naturalist. You can download the app for free from the app store on your phone and upload photos so that researchers can use the information to better understand the timing of the sucker migrations and how climate change could impact this important life-history event. Even if you are fishing offshore and catch a sucker, we still have much to learn about where various species are located at different times of the year. All this information leads to an increased appreciation of suckers and informs better conservation management that considers annual migrations, seasonal habitat use, and the interconnectedness of various species.
Photo credit: Karen Murchie, Shedd Aquarium
MICHIGAN Trout
Love Trout? Thank a Sucker!
