Motoring up on a scenario like this, manta rays feeding on the surface near a marker buoy, almost guarantees you'll be casting at cobia.

Frustration was starting to set in. We’d been running from thunderstorms all morning, and were now caught just off the beach between two large systems—one to the south and one to the north. To make matters worse, it was nearly 10 a.m., and despite some serious searching, we hadn’t caught a single baitfish.

Pinned between two storms my options were to wait it out where we were or run east in hopes of finding something to fill the livewell. I opted to continue the hunt for bait.

Three miles off the beach the water turned from a milky green to a clear blue and the current was honking, pushing the two water densities against each other and creating a well-defined edge that was littered with small clumps of sargassum. Periodically, Spanish sardines flicked across the surface of the colored edge.

“We’re in there,” I told my fishing partner. “All the bait must be stacked along this edge eating the food pushed up by the colliding currents.”

Our sabiki rigs were filled on every drop and the livewell started to look like a small aquarium when Tom pointed out a pair of fins moving directly toward the boat.

“Are those sharks?” he asked, pointing toward the fins with his rod.

The triangular fins bobbed up and down in the waves, and then one flashed white.

“Manta ray,” I replied. “Those are its wing tips. The white is its underside.”

The immense ray glided by the boat hugging the clear blue side of the color change, obviously taking advantage of the concentration of plankton brought to the surface by the currents. Oddly, the big ray had its entire body on the surface, and kept poking its face in the air so that its mouth could filter the top six inches of the water column. Even in the gray light we could see the brown shapes holding under the ray as it passed just a few yards from the boat.

“Cobia!” I shouted. “Grab your spinning rod.”

Even when specifically targeting cobia, the sight of a half-dozen 30- to 50-pound fish hugging the underside of a ray will throw a little adrenaline boost into most anglers, and by the time Tom had a sardine on his rod he also had the rig on his sabiki rod firmly attached to his pants cuff and both his shoes.

I freed him with surprisingly minimal effort, and we eased the boat up the color change to the ray. When the sardine hit the water, all six fish raced for it. A 35-pounder sucked it in and turned to rejoin the ray.

Tom set the hook, which stopped the cobia in its tracks where it violently shook its head while Tom struck again, sending the fish diving for the bottom. On 12-pound tackle the fish took around a half hour to land, and while we fought to regain 50 yards of line manta rays started popping up along the color change in ever-increasing numbers. By the time we threw the cobia into the fish bag, we could see over 20 of the big rays surface-feeding along the blue edge.

It was obvious that the color change is what drew those manta rays, as each ray worked the surface layer within 100 yards of the well-defined edge. All the fish were skimming the surface with their mouths puffed out in a giant oval plankton sieve. But it’s not only the deepwater color changes that attract rays.

On a regular basis I’ve found manta rays swimming along the tidelines off the St. Lucie, Fort Pierce and Jupiter inlets. In these areas, the outgoing tide brings discolored, often brackish water out the inlets where it meets ocean tidal currents, creating a definitive color change. Here the rays don’t skim the surface like the fish we found offshore last May; instead, the rays swim down two or three feet, along the clean side of the edge. As with the offshore fish, these rays have their mouths stretched out to the point that it’s obvious they’re straining plankton.

Cobia hit a variety of lures; shock leader protects against line chafing on the fish's rough mouth.

The rays that run the inlet color changes usually aren’t the immense, mature fish with the 10- to 12-foot wingspans you’ll find offshore, but they’re certainly large enough to hold a cobia or two. And with the smaller rays the cobia can’t tuck up under the wings where they’re difficult to spot.