Reading Sea Surface Temperature Charts for Offshore Fishing

How do you set the temperature range so a break stands out?

Set the color scale on your sea surface temperature chart to the temperatures that actually occur where you fish. A wide default scale spreads the colors thin and blurs the edge. A narrow one puts the full color range across the water that matters, so temperature breaks show up sharp enough to navigate to.

Off Orange Beach, the default scale for the area ran 55 to 78 F. Thomas Hilton matched the cool and warm colors on the image to the scale and narrowed it to 63 to 73. Anything colder painted black, anything warmer painted dark maroon, and a clean edge appeared that he said would be a weed line if there was any sargassum around. He also reads the time stamp on every pass. The satellites report in Greenwich time, six hours ahead of Central, so 22:09 is 4:09 in the afternoon.

How do you tell whether a temperature break is moving?

Compare the same break on two passes several hours apart, painted on the same temperature scale. If it hasn't moved, it's more likely to hold fish. If it has, measure how far and which way, and plan for where it will be when your boat arrives, not where the last image put it.

In the video, Hilton marks the rip as a route, about 88 and a half nautical miles of it, then pulls up a pass from almost 11 hours earlier. Measured along one bearing from a rig waypoint, the rip had moved from 16 to almost 19 miles out, close to 3 miles, about a quarter knot, and it was heading offshore and further south. With the boat still 11 hours from getting there, he expects the rip to be well past the rig it had been sitting inside of. "The longer it's in one spot, the more chances that there's going to be fish on it."

In what order do Orange Beach captains check the charts before a trip?

Most captains start with whatever will decide the day and narrow from there. Around the deepwater rigs of the northern Gulf of Mexico, that means the structure first, then water color, upwelling, current and finally the temperature break, matched against the structure it touches.

Captain Michael Roberto starts by making sure the rig is still there, because floating rigs move and you can run to one you fished two weeks ago and find open water. Then chlorophyll for water color, which he uses for confidence more than as a rule, since fish bite in blue-green water all the time. Then altimetry for upwelling, then current, because "we don't like fishing stagnant pools of water," and last the SST break beside a structure, which centralizes the search. Before satellites, he says, you pointed the boat at the compass rose on the chart and went to see what you could find.

Inside the video

• The default scale versus a narrowed 10 degree window
• Reading pass time stamps in Greenwich time
• Marking a rip with up to 12 route points and saving it for offshore
• Measuring how far a rip moved between two passes
• Daytime and nighttime swordfish drift zones over bathymetry
• Captain Michael Roberto's checklist before a rig trip

SST Chart Questions

Temperature Is One Layer

A break is a starting point, and the captains read it against color, altimetry and current before they commit. The basics of reading temperature charts are in how to read SST charts for fishing.