Lake Superior is the largest freshwater lake in the world by surface area, covering over 31,700 square miles. It is also the deepest and coldest of the Great Lakes, reaching a maximum depth of 1,333 feet. The lake’s massive scale and frigid, nutrient-poor environment, known as an oligotrophic system, supports a unique assembly of aquatic life. Although the cold temperatures and clarity make the water less productive than other lakes, the species that thrive here often reach impressive sizes.
The Largest Fish Species in Lake Superior
The largest native fish species in Lake Superior is the Lake Sturgeon (Acipenser fulvescens). This species holds the title due to its bulk, size potential, and longevity among all Great Lakes fish. Individuals can reach lengths of up to eight feet, with maximum recorded weights exceeding 300 pounds. The Lake Sturgeon is one of the longest-lived fish species in North America. Females may survive for 80 to 150 years, while males generally live for around 55 years.
Characteristics of the Lake Sturgeon
The Lake Sturgeon has a distinctive, prehistoric appearance, tracing its lineage back approximately 150 million years. Its body is covered not in scales but in five longitudinal rows of bony plates called scutes. These scutes offer protection to its elongated, torpedo-shaped form. The sturgeon is a benthivore, meaning it is a bottom-feeder that relies on specialized sensory equipment to navigate the lake floor.
Four sensitive barbels hang near the sturgeon’s snout, which drag across the substrate to locate food. Once prey is detected, the sturgeon extends its tubular, toothless mouth to vacuum up organisms from the mud and sediment. Its diet consists primarily of small, soft-bodied invertebrates like insect larvae, crayfish, leeches, and snails.
The sturgeon’s life cycle is characterized by slow growth and late maturity, which contributes to its size potential. Males reach sexual maturity between 15 and 20 years old, while females typically mature between 20 and 25 years of age. Spawning migrations occur in the spring, with adult fish moving into fast-flowing rivers or congregating over rocky shoals. Female sturgeon reproduce only once every four to seven years, a reproductive pattern that makes the species vulnerable to population pressures.
Other Large and Notable Fish
While the Lake Sturgeon is the largest species, the Lake Trout (Salvelinus namaycush) is the most substantial predatory fish found in Lake Superior’s deep waters. These native char are the top predators in the food web and are known for reaching significant sizes. The largest Lake Trout recorded in Lake Superior weighed 63 pounds, though the average mature size is considerably smaller.
Several other species also grow large. The Muskellunge, or Muskie, is a formidable predator that can grow up to six feet long and is found in coastal habitats. Chinook Salmon, an introduced species, thrive in the cold environment and occasionally reach weights near 50 pounds. Lake Whitefish, a commercially important native species, typically weigh less than 10 pounds but have been documented to reach sizes over 20 pounds.