Our images are tuned to show phytoplankton. Phytoplankton are the microscopic plants that are the bottom of the food chain in the ocean.
Small fish eat the plankton, medium fish eat the small fish and so on.
The more phytoplankton in the water, the cloudier the water is. Now, for fishing, purposes, you want to put your boat in an area were there is a front, or in other words, where the ocean color changes rapidly. One problem with these images is that the satellite cannot see through clouds. This image has some clouds marked, but sometimes it is difficult to tell if you are looking at a cloud or data. To figure this out, simply look at an image from the day before or after the day in question.