Fish kill dead zones in the gulf are mainly created by the nitrogen and phosphorus enrichment of the Lower Mississippi River. Some species of fish exhibit mass simultaneous mortality as part of their natural life cycle. Fish kill due to spawning fatalities can occur when fish are exhausted from spawning activities such as courtship, nest building, and the release of eggs or milt (sperm). Fish are generally weaker after spawning and are less resilient than usual to smaller changes in the environment. Examples include the Atlantic salmon and the Sockeye salmon where many of the females routinely die immediately after spawning. A
Fish meal be made from almost any type of seafood, but is generally manufactured from wild-caught, small marine fish that contain a high percentage of bones and oil, and are usually deemed not suitable for direct human consumption. The fish caught for fishmeal purposes solely are termed "industrial". Other sources of fishmeal are from bycatch and byproducts of trimmings made during processing (fish waste or offal) of various seafood products destined for direct human consumption. The main fish sources by country are: It takes 4 to 5 tons of fish to produce one ton of fish meal; about 6 million tons of