In a fresh water hazard in North Atlantic ocean dramatic declines in fisheries observed most because of migratory birds, pollution, habitat loss and over fishing.
Step-by-step explanation:
North Atlantic Ocean is a rich fishing zone. But in fresh water hazards oceanic or marine salty water also suffered a lot. Seasonal variation in coming of migratory birds in the ocean, water pollution due to oil spill (accidental leakage of oil from ship) and habitat loss for pollution, over fishing (doing fisheries in the same zone repeatedly lessens the number fishes) etc.
Over fishing of same species of fish reduces the number of fishes in that particular zone which hampers the aquatic ecosystem also. Because each marine animal is a food for other animal in the food chain hierarchy.