Domestic and industrial sewage along with oil, sediment and any other chemicals that can be found on the streets run directly into the nearby waters in most cities. All of these waters carrying our waste empty into the ocean, this is huge problem if thought of on the global scale at which it is happening. Aside from pollution overfishing the single greatest problem facing our global fisheries is that of habitat destruction, in particular the destruction of coastal zone habitats. With the demand for ocean harvests increasing, human activities are exploiting these areas at a devastating pace. In the Saltmarshes and Mangroves the vegetation acts as a trap for nutrients, shrimp, many finfish, and also serve to filter pollutants.
Estuaries are probably the most important area, and also the most delicate and affected.
This usually places them in areas of high human activity. These areas are the most productive areas in terms of fish life. Estuaries are estimated to generate 80 million tons of fish per year. This is more than the entire catch from the open seas. However these areas are under great stress due to human activities, and are in jeopardy of being further destroyed.