Lake Mead, the reservoir created by the Hoover Dam on the Colorado River, sustains a diverse population of fish despite its desert environment. This deep, clear, man-made body of water spans Nevada and Arizona. It hosts species ranging from popular sport fish to rare, protected natives. The current fish community resulted from human intervention, including intentional stocking and the change from a turbid river to a deep, cold lake.
The Dominant Game Fish
The most prominent species in Lake Mead are non-native fish, introduced to establish a recreational fishery. Striped Bass (stripers) are the featured sport fish, highly sought after, with some catches exceeding 40 pounds. These schooling predators thrive in the reservoir’s open waters, feeding on introduced threadfin shad.
Largemouth Bass and Smallmouth Bass are also fixtures of the fishery. Largemouth Bass prefer shoreline protection and weedy coves, while Smallmouth Bass inhabit rockier, deeper sections. The lake also supports Channel Catfish and two types of crappie (black and white).
Surviving Native Aquatic Life
In contrast to the thriving non-native game fish, native aquatic life in Lake Mead links to the original Colorado River ecosystem. The Razorback Sucker, an endangered species, is the most notable native fish with a self-sustaining population. This large, long-lived fish is identified by the distinct bony keel behind its head, a feature evolved for the pre-dam river’s turbid conditions.
The Razorback Sucker population is significant because it completes its life cycle here without constant artificial stocking. The protected Bonytail Chub may occasionally be found, but its populations are sensitive. Flannelmouth Suckers are also present near river inflows, though they do not flourish in the deep reservoir conditions. Their survival is actively monitored by wildlife management agencies.
Water Level Dynamics and Fish Habitat
The fluctuating water level of Lake Mead is a defining factor in its aquatic ecology, creating a challenging environment for all fish species. Dropping levels reduce suitable spawning habitat, especially for fish like Largemouth Bass that rely on shallow water and aquatic vegetation. Rapid recession exposes nests, leaving eggs and young fry vulnerable to drying out or predation.
The periodic exposure of the lakebed can provide a temporary benefit by allowing new vegetation to grow. When water levels recover and re-submerge this growth, the flooded plants create excellent cover and habitat for baitfish and juvenile game fish.
The lake’s thermal properties are affected by stratification during the summer, forming distinct temperature layers. This creates a warmer surface layer and a cooler, deeper layer, with the thermocline typically found between 20 and 30 meters. In the deeper layer, dissolved oxygen levels can become depleted, limiting usable habitat. Prolonged low water levels also decrease the volume available for dilution, which can lead to a higher concentration of environmental contaminants.