Charrs, glaciations and seasonal ice

摘要: Although the paleontological evidence is sketchy, genus Salvelinus appears to have arisen some 5–10 million years (My) ago. During most of last 0.6 My, and for a long period before that, charrs existed in periglacial environments just beyond fringes great ice sheets. The eastern North America evolved live close intimate association with all its various natural forms. aquatic which they were cold, unproductive, sediment laden, often catastrophically unstable. Even during times like current interglacial, seasonal conditions influence their environment. Ice can limit movement confine fish winter groundwater fed refuge areas rivers or deep waters. In rivers, spawning grounds may be delimited by suitable upwellings needed protect eggs embryos from ice. lakes, thickness and, often, help define occur molded glacial deposits. Not surprisingly, many traits displayed American recognized as beneficial cold regions. Particularly valuable opportunistic, exploratory, migratory behaviour helps life history. These presumably selected would been useful dispersal whenever sheets retracted. It unlikely these will promote survival under present circumstances when human activity rapidly modifying However, should modern technology enable necessary information obtained guidance, society responds appropriately, it possible persist into future.