Complex sentence: There have been studies that show how the state of the ocean is causing fisheries to collapse, and in areas where fisheries have not yet collapsed, the amount of over fishing that is done is having a significant impact on the industry.
Split into simpler sentences: There have been studies that show how the state of the ocean is causing fisheries to collapse. Even in areas where fisheries have not yet collapsed, the amount of over fishing that is done is having a significant toll on the industry.