You might start by reading a recently published book by one of the leading authoritys on Pacific Salmon and there present day decline, Salmon Without Rivers by Jim Lichatowich. After you read the book you might want to prioritize the various factors in the decline of the Pacific Salmon and write your paper accordingly.
Good luck and I am sure that all the information that Jimm documents in his book will give you enough cross references to write 10 senior papers.