Albacore tuna is higher in mercury than canned light tuna because canned tuna is largely younger, smaller fish that haven't absorbed as much mercury.

CNN: Seafood benefits outweigh risks, government says

"You never know when you are going to sight a fish you haven't seen before, " said Peter Leahy, an amatuer diver who has been participating in the fish count for the last seven years.

CNN: Counting fish adds up for marine protection