Complex sentence: The region is very rich in marine mammals (seal and beluga), fish (Arctic char, Atlantic salmon, trout), ducks (particularly eider ducks) and many seabirds; also, close to 1000 musk-ox roam the surrounding area.
Split into simpler sentences: The region is very rich in marine mammals (seal and beluga), fish (Arctic char, Atlantic salmon, trout), ducks (particularly eider ducks) and many seabirds. As well, close to 1000 musk-ox roam the surrounding area.