Lake trout, also known as lakers or mackinaw, are prominent freshwater predators found across North America in cold, deep lakes. These fish are significant components of their aquatic ecosystems, serving as apex predators in many environments. Understanding their diet provides insight into their ecological role and the health of the food webs they inhabit.
Primary Food Sources
Adult lake trout are primarily piscivorous. Common prey species include ciscoes, also known as lake herring, which are a favored food in large bodies of water like the Great Lakes. Smelt, sculpins, yellow perch, and various whitefish species also constitute significant portions of their diet in many regions. Other fish such as alewives, round gobies, chubs, minnows, and suckers are consumed depending on local availability.
Beyond fish, lake trout also consume a variety of invertebrates. These include crustaceans like Mysis shrimp and amphipods, along with larger invertebrates such as crayfish and leeches. Aquatic insects in both larval and adult forms, including mayfly nymphs, caddisflies, midges, dragonflies, and damselflies, are also part of their food sources.
Dietary Changes and Influences
A lake trout’s diet changes significantly throughout its life stages. Newly hatched fry subsist mainly on zooplankton and microscopic invertebrates. As they mature into juveniles, their diet expands to include larger invertebrates and aquatic insects. This transition marks the beginning of their shift towards consuming smaller fish, a diet that becomes dominant once they reach adulthood.
Seasonal changes also influence what lake trout eat. In spring and fall, lake trout often forage in shallower, nearshore areas where prey, such as minnows and suckers, are more abundant. During the warmer summer months, they tend to move to deeper, cooler waters, which can lead to a reliance on different prey species that inhabit those depths. In winter, their activity slows, but they continue to feed in deeper waters, targeting available fish and invertebrates.
The specific habitat and depth a lake trout occupies directly impact its food choices. In deeper, open waters, they often rely on pelagic fish species that form schools. Conversely, shallower habitats may offer a wider array of invertebrate prey or smaller, bottom-dwelling fish. The overall availability of prey species within a given lake is a primary determinant of the lake trout’s diet.
Foraging Strategies and Habitat
Lake trout are well-adapted predators, employing various strategies to capture their food. They possess keen eyesight and an advanced sense of smell, enabling them to detect faint chemical cues from prey. Their swift, powerful movements allow for effective pursuit and capture of active prey.
These fish prefer cold, oxygen-rich waters. This habitat preference influences their prey selection, as many of their preferred food sources also inhabit these cooler depths. Lake trout exhibit both ambush predation tactics, waiting for unsuspecting prey, and active pursuit, especially when targeting schooling fish in open water. Their diet is intimately connected to the availability of suitable prey within their specific cold-water environments.