The tuna rods were rigged and securely stowed, and we had plenty of ice in the fish box. All packed and ready to roll, we would surely arrive at the blue-water grounds in time for the morning bite. There was still one last thing to check, though. We snuck back inside, fired up the laptop and logged on to our favorite website for tracking Gulf Stream conditions. Come on, baby, give us an update on those satellite images! 

ROFFS charts actually label potential fishing "hot spots," such as cold-water eddies

Sound familiar? It should.
 
More than ever before, serious offshore fishermen monitor oceanic conditions such as sea-surface temperatures (SST) and chlorophyll levels. Understanding the dynamics of seawater and how fish relate to their constantly changing environment - especially in an age of heavily fished oceans - is fundamental for today's anglers in search of fast-moving pelagics such as tuna, mahi and billfish. Likewise, as fuel prices remain at unprecedented levels, knowing which direction to point the boat in search of the most favorable conditions will save anglers precious cash as well as valuable time on every trip.
 
The good news for fishermen: Never before has ocean-condition data been more widely available. Maps overlaid with satellite images from the National Oceanic and Atmospheric Administration (NOAA) are accessible through countless websites. Some sites are free and simply re-purpose the images, while others provide anglers with more detail and crucial alignment capabilities for a price. Regardless, all offshore fishermen should view these products and services as vital fishing tools, every bit as important as depth finders, radar and GPS.

Cool Edges and Hot Pockets
Spring means tuna time for Capt. Ed Dwyer (321-631-3321, www.ticketfishing.com) of Port Canaveral, Florida. Dwyer spends these days running to the "Other Side," a fishery he discovered along the eastern edge of the Gulf Stream that serves as an Atlantic highway for northerly-migrating yellowfin.
 
Understanding sea-surface temperature boundaries proves vital to locating and catching these tuna. Most times, yellowfin travel just outside the warm corridors of the Gulf Stream, where they pick off bait in adjacent, cooler waters.
 
Focused on finding critical temperature breaks each night prior to a charter, Dwyer studies the latest satellite imagery at www.sstcharts.com to pinpoint the edge.
 
"I like to see a fairly drastic change in temperature," says Dwyer, who operates the Ticket, a 60-foot Paul Spencer. "That tells me there will be a good edge, good current and bait concentrations. The majority of the tuna will be in that area, as well. The more dramatic the temperature change, the better. I've seen a 5- or 6-degree change, but even a difference of 2 or 3 degrees attracts fish."
 
Regardless of the fishery, better conditions typically occur along more extreme temperature boundaries, says Mitchell Roffer, Ph.D., renowned marine scientist and proprietor of Roffer's Ocean Fishing Forecasting Services (ROFFS). But an even more crucial factor involves the length of time a strong boundary has existed. As frontal boundaries build, plankton, debris and eventually bait get sucked into the vicinity, offering valuable time for roaming pelagics to locate easy meals.
 
"If you find a strong break that's only been there one day, you might catch some fish. But if it's been there four or five days, you'll have good fishing," explains Roffer, whose company offers not only cutting-edge satellite-imagery maps, but has also written fishing analyses, advising where best to locate fish given daily conditions. 
 
On the Pacific coast, temperature changes play a key role in locating pelagic species,   but in general, the temperature disparity between current edges is not nearly as   dramatic as along the Atlantic's Gulf Stream.
 

Terrafin's SST and chlorophyll charts are especially popular among West Coast anglers.

Capt. Mike Lackey (619-224-6500, www.vagabondsportfishing.com), a long-range charter operator out of San Diego, California, relies on SST charts during summer months when searching for temperature-sensitive albacore and bluefin tuna. The only drawback during this time of year comes in the form of heavy cloud cover, which blocks satellite pictures. Interference from atmospheric conditions represents the biggest bug-a-boo anglers encounter when utilizing these charts,  especially those associated with free websites.
 
When sunny skies rule, however, Lackey turns his attention to www.terrafin.com, one of the more popular fee-based providers on the West Coast.
 
"As much as edges, we watch to see how pockets form," he says. "When they're on an edge, fish can string out along 100 miles. But when the fish are trapped in a pocket, you have them locked down a little better."
 
Seamounts create upwellings in these waters, which spawn the warm-water pockets. The pockets open and close like pinwheels, Lackey says, and while they may measure only a half-degree warmer, bluefin and albacore come up along with them, offering plenty of opportunity for anglers.