Salinity charts read with Thomas Hilton: why the imagery is debated, what the green mixing water and the salty red zones mean, and how kingfish and tuna anglers use it near freshwater influxes. Captain Michael Roberto explains why he checks the charts before every trip.
How to Read Salinity Charts for Fishing Forecast
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Instructor:
Thomas Hilton
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Are satellite salinity charts reliable for offshore fishing?
Salinity charts are useful but limited. Satellites read only a thin layer at the surface, so a chart can show fresh water where the water a few feet down is fully salty. Use them to spot big freshwater influxes and mixing zones, and confirm what they show with temperature and water color before you run.
Thomas Hilton opens with that caveat himself. There's some debate about the value of salinity imagery because it measures only the surface: "it could be fresh on top and be salty three feet down." He still keeps it in the toolbox, mainly for kingfish anglers, and for one clear job: seeing where big influxes of fresh water are pushing out and staying off the ultra-fresh zones.
Thomas Hilton opens with that caveat himself. There's some debate about the value of salinity imagery because it measures only the surface: "it could be fresh on top and be salty three feet down." He still keeps it in the toolbox, mainly for kingfish anglers, and for one clear job: seeing where big influxes of fresh water are pushing out and staying off the ultra-fresh zones.
What do kingfish and tuna anglers look for on a salinity chart?
Kingfish anglers watch where fresh water pushes out from rivers and stay off the ultra-fresh water. Tuna anglers look for the mixing zone, where the water is a little fresh and less salty than the open ocean. On the chart in this video that mix shows as green, and extremely salty water shows as red.
Hilton says it plainly: a lot of anglers who target tuna like to look for the green. The chart he works is off Orange Beach, where river water pushes into the northern Gulf of Mexico, and he points out both the freshwater influxes to avoid and the extremely salty red zones. Captain Michael Roberto adds that inshore anglers can use the same charts, because salinity levels show where kings and other species like to congregate.
Why log your catches on the satellite charts?
Logging catches against the charts turns a good day into a pattern you can find again. Mark where a fish was caught on that day's images, and later you can see what the temperature, color, altimetry and salinity looked like at that spot, then look for the same setup on the next trip.
In the video, Hilton drops a waypoint where a tuna was boated, labels and dates it, and chooses whether the icon shows on every image or only on that day's. Over a season that builds an archive of where fish came from and what the water was doing. Captain Michael Roberto's view of the whole process is blunt: if you're not looking at the charts before you head off, "you're doing a disservice to yourself and the crew." To him it's a cheat sheet that gives the crew a head start and raises everyone's confidence before the boat leaves the dock.
Inside the video
- Why salinity imagery is debated, and the surface-only limit
- Freshwater influxes and ultra-fresh zones to avoid
- Reading the green mix and the salty red
- Logging a catch on the chart and building an archive
- Captain Michael Roberto on using the charts inshore and offshore
Salinity Chart Questions
What do the colors mean on a salinity chart?
On the chart in this video, green marks mixed water that is a little fresh and less salty, and red marks extremely salty water. Other services use different color scales, so read the legend before you read the water.
Why can a salinity chart mislead you?
It reads only the surface. A chart can show fresh water on top of water that is salty a few feet down, where the fish may be holding. Treat it as a guide to where fresh water is pushing out, and check it against temperature and color.
Do salinity charts help inshore anglers?
Captain Michael Roberto thinks so. He recommends them to inshore anglers for showing the salinity levels where kings and other species congregate. Offshore, salinity is a supporting layer next to temperature, color and current rather than the first chart to check.
Salinity Is a Supporting Layer
Salinity tells you where the fresh water is; the other charts tell you whether the fish are there. How satellite charts help with king mackerel and the offshore species is in planning tuna, wahoo and marlin trips with satellite charts.
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There are no reviews yet.Thomas Hilton
Thomas Hilton is the founder of Hilton's Realtime Navigator and the pioneer of satellite fish mapping for offshore anglers. Nearly two decades ago he turned newly available ocean data into a service now considered standard by bluewater tournament teams and top charter captains. In his In The Spread videos, Hilton teaches how to read sea surface temperature, chlorophyll, altimetry, salinity, and currents, and how to combine those layers and plan fuel-smart trips that put you on tuna, marlin, and other pelagics across the Gulf, Atlantic, and Pacific.
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