This is not only because harvesting from relatively shallow waters is easier than in the open ocean, but also because fish are much more abundant near the
coastal shelf,
due to
coastal upwelling and the abundance of nutrients available there.
These include eastern boundary current
upwelling systems such as those off the U.S. west coast along
coastal California, Oregon and Washington, deep - sea and subsurface oxygen minimum zones, and
coastal waters that are already experiencing excess nutrient levels (eutrophication) and low dissolved oxygen (hypoxia)
due to human - driven nutrient pollution from land - based activities.
increased CO -LCB- sub 2 -RCB- by using ocean models that include realistic processes such as horizontal heat transport, vertical mixing
due to convection and small - scale processes, and
upwelling along
coastal regions and the equator.