What is the biggest fish in Lake Superior?

Lake Superior, the largest and deepest of the five Great Lakes, is home to a diverse range of aquatic life. With its cold, clear waters, it supports many species of fish, both native and non-native, that vary in size. Among these species, there is one fish that stands out for its sheer size and iconic presence: the lake trout (Salvelinus namaycush). Known for its impressive size and status as a top predator in the lake’s ecosystem, the lake trout holds the title of the biggest fish in Lake Superior.

Lake Trout: The Largest Fish in Lake Superior

The lake trout is the largest fish species in Lake Superior, capable of reaching lengths and weights that make it a true giant in the lake’s cold, deep waters. This fish is a native species to the lake and is deeply ingrained in its history and ecosystem. It is a cold-water species that thrives in the deeper, oxygen-rich waters of Lake Superior, making it well-suited to the conditions of this massive and remote lake.

Size and Appearance

Lake trout can grow to enormous sizes, with some individuals reaching lengths of up to 50 inches (127 cm) and weighing more than 40 pounds (18 kg). Though fish of this size are rare, they have been documented, particularly in the deeper, colder regions of the lake. The average lake trout, however, typically ranges between 20 to 30 inches in length and weighs between 5 and 15 pounds.

Lake trout have a distinctive appearance characterized by their long, torpedo-shaped bodies, large mouths, and sharp, carnivorous teeth. Their skin is typically dark olive or gray, adorned with lighter spots that are most prominent on their back and sides. These spots, often referred to as “vermiculations,” are one of the defining features of lake trout. Their tail fin is forked, which is typical of salmonid species.

Habitat and Distribution in Lake Superior

Lake trout are most commonly found in the deeper parts of Lake Superior, especially in waters that are colder and rich in oxygen. As a cold-water species, they prefer water temperatures of around 50°F (10°C), which is why they thrive in the lake's deep, frigid waters. Lake Superior, with its maximum depth of 1,332 feet (406 meters), provides the perfect environment for lake trout, as the deep waters ensure year-round cold temperatures.

Lake trout are often found in depths of 100 feet (30 meters) or more, where the water temperature remains ideal. In the warmer summer months, they may move into shallower waters to spawn or hunt, but they typically retreat to the deeper, cooler waters of the lake when temperatures rise.

Behavior and Diet

Lake trout are apex predators in Lake Superior, occupying the highest trophic level of the lake’s food web. Their diet consists primarily of smaller fish, such as ciscoes (lake herring), yellow perch, smelt, and juvenile lake trout. They are opportunistic hunters and will feed on whatever fish are abundant in the area. Their sharp teeth and strong jaws allow them to capture and consume prey with ease. Additionally, they are known to feed on invertebrates such as crustaceans when fish populations are scarce.

Lake trout exhibit a variety of feeding behaviors, including ambushing smaller fish in open water and stalking prey near the lake bottom. They are solitary creatures and tend to hunt alone, unlike some species of fish that live in schools.

Reproduction and Lifespan

Lake trout are known for their relatively slow growth rates and long lifespans. They typically live for 15 to 25 years, but some individuals have been known to live even longer. A lake trout’s growth rate can vary depending on environmental factors like water temperature and the availability of food, with fish in colder waters typically growing more slowly.

Lake trout spawn in the fall, typically between late September and November. They lay their eggs on rocky substrates in deep waters, where the eggs can remain undisturbed throughout the winter. After fertilization, the eggs hatch in the spring, and the young lake trout begin their long and slow journey toward maturity. The young fish start by feeding on smaller prey like zooplankton and insect larvae before transitioning to fish as they grow larger.

Conservation and Management

Lake trout populations in Lake Superior have faced significant challenges over the years. Historically, overfishing, the introduction of invasive species like the sea lamprey, and habitat degradation contributed to declines in their numbers. The sea lamprey, a parasitic species that preys on lake trout by attaching itself to the fish and feeding on its blood, had a devastating effect on lake trout populations.

Efforts to restore and protect lake trout populations have been ongoing for decades. These efforts include the use of chemical treatments to control the sea lamprey population, habitat restoration, and fish stocking programs. Today, lake trout populations in Lake Superior are considered to be relatively stable, though ongoing monitoring and management efforts are essential to ensure the long-term health of the species.

In addition to restoration programs, fishing regulations in Lake Superior are designed to protect lake trout populations. These regulations often include limits on the number of fish that can be caught, restrictions on fishing in certain areas, and size limits to ensure that juvenile fish are allowed to grow to maturity before being harvested.

Other Large Fish in Lake Superior

While the lake trout is the undisputed largest fish in Lake Superior, other notable species also grow to impressive sizes. These include:

1. Pike (Esox lucius)

The northern pike is another large predator found in Lake Superior, particularly in the shallow, weedy areas near the shore. While pike generally do not reach the same size as lake trout, they can grow to lengths of up to 40 inches (102 cm) and weigh as much as 20 pounds (9 kg). Northern pike are ambush predators that hunt smaller fish, and they play an important role in controlling the populations of species like yellow perch and minnows.

2. Walleye (Sander vitreus)

The walleye, though not native to Lake Superior, has established a healthy population in the lake, particularly through stocking programs. Walleyes can grow to considerable sizes, with some individuals reaching lengths of 30 inches (76 cm) and weights of over 10 pounds (4.5 kg). Walleyes are predatory fish that hunt fish and invertebrates, and they are highly prized by anglers.

Conclusion: Lake Superior's Giant

The lake trout is the largest fish species in Lake Superior, a true giant of the Great Lakes ecosystem. With its remarkable size, predatory habits, and historical significance, the lake trout embodies the vastness and complexity of Lake Superior's ecosystem. Though populations of lake trout have faced challenges over the years, conservation efforts have helped restore and stabilize their numbers, ensuring that future generations will continue to witness the majesty of this incredible fish.

For those who venture to Lake Superior to fish, observe, or appreciate the natural world, the lake trout stands as a reminder of the lake's remarkable biodiversity and the efforts required to protect and sustain it.