Fishermen Help

How to Understand Surface Current Radar (CODAR)

(printable version)

What is CODAR
There are many types of Surface Current Radars. The one we use is called CODAR which stands for Coastal Ocean RADAR. The image below is typical of the data we receive from CODAR.

Our CODAR system consists of a series of antennas (shown here) at seven sites along the New Jersey Coast. These antennas measure the surface currents of the ocean using radio waves. In the image above, you can see a piece of the southern New Jersey coast, and a large group of arrows offshore. The size of the arrows represents the speed of the current, as does the color (red=fast, blue slow), and the direction the arrow is pointing is the direction of the surface current. Not too difficult, huh? In this image, all the surface currents are moving to the southwest.

How to Find Fish using CODAR
On any day of the year, there is plenty of algae floating on the ocean surface. These plants are food for small fish. The small fish are food for medium size fish. Finally, the medium fish are food for the big boys (Tuna, Mahimahi, etc). So, if you think about it, generally speaking, wherever there's a lot of seaweed at the surface, you will probably find some sort of big fish down below. The tough part is finding these seaweed lines.

As explained in the satellite image tutorial, big fish tend to be found near areas where water converges at the surface, meaning the area where two different water masses push toward each other. So, what you want to look for in a CODAR image is an area where the arrows tend to point toward one another. In next image, there are a couple of areas where you would probably find some fish down below. Area A and B are two places where the arrows push in toward one another. Now, they are not directly facing one another, but there is enough of an angle between the currents to suggest that there would be a seaweed or foam line at the surface.

In these convergence zones, the surface water, and everything in it, pushes together. When two water masses push towards one another it acts like two conveyor belts facing each other. But seaweed and algae float so they begin to pile up at the surface in large lines. Got it? The bottom line: Wherever you can spot currents pushing towards one another, there are probably some fish underneath feasting on the algae buffet at the surface.

You can also lean more about how CODAR works.