Complex sentence: At that time, the nearby Wieprz river was abundant with Eurasian beavers, the animals which due to their precious furs were regarded as royal property, were protected from hunting by royal officials, known as bobrownicy (hence the name of the village).
Split into simpler sentences: At that time, the nearby Wieprz river was abundant with Eurasian beavers. These animals were regarded as royal property because of their precious furs and were protected from hunting by royal officials, known as bobrownicy (hence the name of the village).