Lake trout are cold-water fish with predatory feeding habits in North America. Their diet is diverse, adapting to available prey and changing as the fish grows. This adaptability allows them to thrive across various aquatic ecosystems.
Primary Food Sources
Adult lake trout primarily consume other fish, which form a substantial portion of their diet. Common prey fish include cisco (also known as lake herring), smelt, sculpins, and various whitefish species. In some regions, alewives and yellow perch also serve as significant food sources for adult lake trout. These larger fish provide the necessary energy for the lake trout’s growth and sustained activity as a top predator.
Invertebrates, such as Mysis shrimp, amphipods, and aquatic insect larvae (mayfly nymphs, caddisflies, midges), are important, especially for younger or smaller lake trout. Terrestrial insects also serve as opportunistic prey. Newly hatched lake trout, or fry, rely on zooplankton for early development. While adults primarily eat fish, some lake trout populations consume plankton throughout their lives, often resulting in smaller individuals.
Factors Influencing Their Diet
A lake trout’s diet changes significantly throughout its life stages. Young lake trout, or fry, initially rely on zooplankton, then transition to aquatic insects and small invertebrates as they grow into juveniles. As they mature, their diet shifts towards consuming predominantly fish, reflecting their development into larger, more capable predators. This dietary progression ensures they acquire sufficient energy for growth at each stage.
Seasonal changes also influence the availability of prey and thus the lake trout’s feeding patterns. For instance, in spring, lake trout may feed heavily on certain forage fish or invertebrates that become more accessible in shallower waters. During warmer summer months, lake trout often move to deeper, cooler waters, which can alter the types of prey they encounter and consume. The presence of spawning migrations by certain fish species or insect hatches can provide temporary, abundant food sources.
The specific habitat and the unique characteristics of a lake greatly determine what a lake trout eats. Different lakes possess varying prey populations, depths, and underwater structures, leading to diverse diets among lake trout populations. For example, invasive species like round goby have become a significant food source for lake trout in some Great Lakes regions, especially in spring and fall. Water temperature and dissolved oxygen levels also influence the distribution and activity of both lake trout and their prey, impacting feeding opportunities.
Feeding Behavior and Ecological Importance
Lake trout are opportunistic predators, adapting their hunting strategies to their environment and available prey. They may employ ambush tactics, waiting near underwater structures, or actively pursue fish in open water. Their sensory abilities, including keen sight and a lateral line system, assist them in detecting and tracking prey in their often deep, dark habitats. This allows them to utilize diverse food sources.
As apex predators in their native ecosystems, lake trout maintain the balance of aquatic food webs. Their predation helps regulate the populations of forage fish and other organisms. By consuming various prey, lake trout contribute to the health and stability of their aquatic environment.