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Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in the species becoming increasingly underpopulated in that area.
However, ocean currents also flow thousands of meters below the surface. These deep-ocean currents are driven by differences in the water's density, which is controlled by temperature (thermo) and salinity (haline). This process is known as thermohaline circulation. In the Earth's polar regions ocean water gets very cold, forming sea ice.
The NOAA conducts general research on ocean resources and is responsible for research on the effects of ocean dumping, pollution, overfishing, and other issues caused by humans that cause changes in the marine ecosystem.
The surface salinity of the ocean is a key variable in the climate system when studying the global water cycle, ocean–atmosphere exchanges and ocean circulation, all vital components transporting heat, momentum, carbon and nutrients around the world. [84] Cold water is more dense than warm water and salty water is more dense than freshwater.
Overfishing, which NOAA Fisheries is tasked with preventing, is a major threat to biodiversity, global food security, and the fishing sector. [ 20 ] [ 23 ] The MSA also requires that overfished stocks be rebuilt within 10 years, except in cases where the life history characteristics of the stock, environmental conditions or management measures ...
This prompted major amendments in 1996 and 2006. The National Marine Fisheries Service issued a report to Congress in 2010 on the status of U.S. fisheries. It reported that of the 192 stocks monitored for overfishing 38 stocks (20%) still have fish "mortality rates that exceed the overfishing threshold … and 42 stocks (22%) are overfished". [12]
Overfishing is one of main causes of the decrease in the ocean's wildlife population over the past years. The Food and Agriculture Organization of the United Nation reported that the percentage of the world's fish stocks that are at biologically sustainable levels have decreased from 90% in 1974 to 65.8% in 2017.
Jack mackerel caught by a Chilean purse seiner Fishing down the food web. Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in the species becoming increasingly underpopulated in that area.