The round whitefish boasts a distinctive appearance that sets it apart from other fish species. It features an olive-brown back with light silvery sides and underside, creating an elegant contrast. The fish typically measures between 9 and 19 inches (23 and 48 cm) in length, with a cylindrical body shape. Its scales range from sepia brown to bronze, edged with black, while the lower fins exhibit shades of amber. Notably, the round whitefish possesses larger scales, a smaller mouth, and weak or no teeth, characteristic of its subfamily within the salmon family.
The life cycle of the round whitefish is a fascinating journey, marked by regular migrations and spawning in freshwater tributaries. These fish typically seek out spawning sites layered with pebbles, located below shoreline currents and approximately 1-1.5 meters deep. During spawning, fertilized eggs are held within the spaces between rocks or nestled in the ice crystals of the slushy tributary floor. The round whitefish exhibits subtle sexual dimorphism, with male fish developing pearl organs along their bodies and displaying altered coloration during spawning. Spawning occurs between early October and late November, when the water temperature reaches or dips below 2.5 °C. It's important to note that the round whitefish does not spawn annually, and while first-year spawners may spawn the following year, their spawning frequency is relatively low.
Round whitefish are resilient inhabitants of cold freshwater environments, including Arctic seas, post-glacial lakes, rivers, and brackish waters. Their range spans from the northern waters of North America to the northeastern waters of Asia. Within North America, they can be found in the Great Lakes (excluding Lake Erie), areas of the Arctic Ocean, Hudson Bay, waterways in northern Canadian provinces, arctic brackish waters, and throughout Alaska. Interestingly, round whitefish can adapt to low salinity areas in the Arctic Ocean, thanks to the abundance of rivers and waterways that flow into the region.
Round whitefish are classified as benthivores, primarily feeding on benthos and plankton. Their diet consists of a wide range of prey, including amphipods, gastropods, isopods, chironomid larvae and pupae, and various aquatic insects such as spiny water flea (Bythotrephes longimarus). These fish exhibit a stable feeding pattern, adapting their diet to what is available in their environment. Food availability varies based on location, neighboring species, and the time of year. During migration to spawning sites, round whitefish predominantly feed on spiny water fleas, black fly larvae, and other aquatic insects. It's important to note that round whitefish do not feed during spawning, as they rely on stored energy reserves accumulated prior to the spawning period.
While round whitefish are not a primary target for subsistence or sport fisheries, human activity in their habitats can influence these species. Research studies have been conducted near developing projects to assess the impact of nearshore developments, such as mining, on fish populations. Several factors have contributed to the slight decline observed in round whitefish populations globally, including a decrease in food sources and water quality. Additionally, the effects of global warming, driven by human activity on a larger scale, pose a potential threat to round whitefish. As cold-water inhabitants, these fish may be significantly impacted if ocean temperatures continue to rise. To ensure the preservation of round whitefish populations, conservation measures may need to be considered.