Original:  Despite devastating population losses to European infectious diseases, to which they had no immunity, these Atlantic First Nations held on to their traditional coastal or river locations for hunting, fishing and gathering , and were concentrated along river valleys for trapping.
Revised:  Despite devastating population losses to European infectious diseases, to which they had no immunity, these Atlantic First Nations held on to their traditional coastal or river locations for hunting, fishing and gathering . They lived along river valleys for trapping.
Edit intent: coherence