What french nobleman explorer discovered streams full of beavers?

The French nobleman explorer who discovered streams full of beavers was Pierre Gaultier de Varennes, Sieur de La Vérendrye. He explored the northern regions of North America in the 18th century, particularly in areas that are now part of Canada. His expeditions were significant for their contributions to the fur trade, as beaver pelts were highly sought after in Europe. La Vérendrye's explorations helped to establish French claims in the interior of the continent.