Don’t Be the Blind Squirrel

Optimize Your Time Offshore With Data Rich Satellite Imagery

Capt. Steve Dougherty October 29, 2015

Waterworld, the 1995 movie starring Kevin Costner, wasn’t so far off as it really is a big, big ocean out there. If you don’t have a plan in place before you leave the dock you may get lucky when heading offshore, but odds are you will burn a lot of fuel running around when you could be catching fish. Fortunately, the advent and availability of satellite imagery makes finding potential hot spots much easier. Whether you fish the offshore canyons and rigs in the Gulf, make long runs to locate yellowfin tuna on the eastern side of the Gulf Stream, or fish the reef edge for sails and everything else that thrives there, you can greatly benefit by spending a bit of time interpreting satellite imagery before you leave the dock.

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By utilizing modern technology, savvy skippers are able to locate promising water long before leaving the dock.

While you’ll have to learn what you are looking at, using highly detailed satellite imagery to identify potential fishing spots does not require an advanced degree. If you can surf the web, you can find plenty of resources out there to help you locate promising water, and it doesn’t always require a subscription fee. Terrafin, Clearpoint, ROFFS and Hilton’s Real-Time Navigator all produce data rich imagery and relay important oceanographic conditions, but for its simplicity, organization of key elements and layering abilities I prefer FishTrack.com. They also operate Surfline.com and Buoyweather.com, so by visiting one website I can access all of the most accurate, real-time ocean forecasts from the nation’s leading meteorologists and forecasters.

While cloud-free SST charts are available for free, accessing the premium data and detailed imagery from MODIS, AVHRR and VIIRS satellites costs less than a pack of ballyhoo for a monthly subscription. Anglers know conditions can change significantly in only a few hours, so it’s highly beneficial these satellites transmit multiple images a day to provide the best possible picture of offshore water temperature and chlorophyll concentration levels. Some even provide updated imagery every 90 minutes.

While schedules often dictate your time spent offshore, there are numerous intangible factors to consider when attempting to identify the best days, areas and times to target offshore fish including water temperature and clarity, location of structure, sea surface height, current direction, thermocline depth, salinity, wind strength and direction, tides, moon phase, moonrise and moonset. All of these factors and more greatly influence the movements of offshore game fish, especially billfish, dolphin and tuna, but if you’re just starting to play around with satellite imagery, keep it simple. Focus on the basics—water temperature, water clarity and the presence of structure—to help you locate fish until you become more proficient at understanding the data. This will only come with experience and relating what you observe on the water with the satellite imagery.

In the Gulf of Mexico, water temperatures fluctuate based on the season and currents. Big blue marlin are the main draw for anglers out of Destin and Pensacola, and can tolerate water temperatures in the low 70s, but don’t start to appear in numbers until the water temperature hits the mid to upper 70s. Anglers heading offshore from any port in the Gulf should pull up a satellite chart and locate the Loop Current in relation to reachable rigs and structure. With experience you will be able to identify currents and filaments by studying the sea surface temperatures. Once you’ve identified a body of water in the ideal temperature range you should take into consideration water clarity.

Chlorophyll is the green matter that occurs in plant life and on the surface of the ocean. The higher the phytoplankton concentration, the greener the water, so by viewing the latest chlorophyll images you can pinpoint clean water and color changes. It’s important to note that the food chain starts with these tiny organisms and knowing where phytoplankton blooms occur will give you a really good idea of where there might be large concentrations of baitfish.

Billfish typically prefer cleaner, blue water, while concentrations of bait will often feed in the greener, off-colored waters that teem with smaller organisms. The boundary areas and convergence zones between blue and green water, often referred to as color changes, will typically stack up bait and provide favorable conditions for big game pursuits. You can still catch billfish in green, off-colored water, but there’s a much better chance you’ll find larger concentrations of billfish and tuna in or around the edges of areas where green and blue water interact, or in the blue water itself. As you troll along a color break be sure to monitor your fish finder, check the water temperature, and scan the horizon for noticeable signs of life like weedlines, diving birds, nervous water and scattering bait. Experienced anglers also check the latest satellite images to observe the movement of favorable water and convergence zones and if the conditions are likely to remain favorable.

Structure is the third critical component and may consist of a hump on the bottom, a ledge, a canyon, an artificial reef, an oil rig or FAD. Depending on the nearby bottom features, even the smallest piece of structure can hold the action you seek.

The basic idea is to locate an area where ideal temperature, water clarity and structure all come together. With the latest satellite services I can layer bathymetric charts on top of the SST imagery to find good water on structure. The trick is to find ideal water temperatures along with blue water, especially where clean water is interacting with off-colored water creating a push or boundary. And finally, look for these conditions over an area where structure is present. Find a spot that meets all this criteria and there’s a very good chance you’ll find tuna and/or billfish.

The final piece of the puzzle is the weather, which covers a broad range of environmental conditions including wind, tides, current and lunar phase. Florida is so diverse that no two places fire off in the same exact conditions. With that in mind, it’s best to have every possible tool at your fingertips. The more you know, the better off you are because even just a mile from the bite and you could be spinning your props and wasting your time. Scientific computer models based on high-resolution satellite imagery provide offshore anglers with a wealth of knowledge, so use it!

FishTrack App

Free via iTunes, the new FishTrack app provides users with the latest cloud-free and high-resolution sea surface temperature charts, chlorophyll images, ocean altimetry, currents, bathymetry, moon phase and tides, as well as Buoyweather marine forecasts. After you’ve found an area worth further investigation, the app enables you to plot waypoints and save the chart imagery for use while on scene.

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