Yellowstone Lake, within Yellowstone National Park, is North America’s largest high-altitude freshwater lake, situated at approximately 7,730 feet (2,357 meters). Covering about 136 square miles (350 square kilometers), it has an average depth of 139 feet (42 meters) and a maximum depth of at least 394 feet (120 meters). The lakebed features a vigorous hydrothermal system with underwater geysers and hot springs reaching 170°C (340°F), reminding visitors of the active Yellowstone Caldera beneath.
Native Fish Species of Yellowstone Lake
The dominant native fish species in Yellowstone Lake is the Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri). These trout are identifiable by the distinctive red coloration on the underside of their lower jaw. They can live for up to 11 years and typically spawn in the lake’s tributary rivers and streams from late April through mid-July. Historically, this subspecies was abundant, representing the largest inland population of nonhybridized Yellowstone Cutthroat Trout.
Yellowstone Cutthroat Trout are a keystone species in the lake’s ecosystem. They serve as a primary food source for numerous terrestrial and avian predators, including grizzly bears, bald eagles, ospreys, and river otters. Their spawning migrations provide biomass and nutrients, supporting a diverse array of wildlife. While Yellowstone National Park is home to 12 native fish species, Yellowstone Lake itself historically contained primarily cutthroat trout and only one other minnow species.
Non-Native Fish Species
The introduction of non-native fish species, particularly the Lake Trout (Salvelinus namaycush), significantly disrupted Yellowstone Lake’s ecological balance. These predatory fish were first detected in the lake in 1994, although their illegal introduction is believed to have occurred during the 1980s. Unlike the native cutthroat, Lake Trout are larger and can live for 30 to 40 years. They are also highly fecund, with females capable of producing thousands of eggs annually.
Lake Trout primarily spawn in the deep waters of the lake, making their eggs and young inaccessible to many of the native predators that rely on the shallow-spawning cutthroat trout. Their predatory nature significantly impacted the native Yellowstone Cutthroat Trout population, leading to a decline. A single mature Lake Trout can consume approximately 41 native Cutthroat Trout each year. This predation also affects animals like bears, ospreys, and otters, who historically depended on accessible Cutthroat Trout as a food source.
Protecting Yellowstone Lake’s Fish Populations
Efforts manage and protect Yellowstone Lake’s fish populations, focusing on restoring native Yellowstone Cutthroat Trout and controlling non-native species. The Native Fish Conservation Plan, initiated in 2010, guides these strategies. Gillnetting is a primary method for managing the non-native Lake Trout population, involving long nets in deeper waters to target Lake Trout while minimizing incidental catch of native species.
Since 1995, over 4.5 million Lake Trout have been removed from Yellowstone Lake through suppression efforts. Other methods, such as telemetry and embryo suppression, are also employed to further reduce Lake Trout numbers. These sustained efforts have reduced the Lake Trout population and increased Yellowstone Cutthroat Trout numbers. As a result, predators like grizzly and black bears are increasingly returning to feed on spawning Cutthroat Trout in the lake’s tributaries. Public involvement, including anglers targeting non-native fish, also contributes to these conservation goals.