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How to Tell Whitebait and Threadfin Apart

It's the time of year for sardines and herrings to invade Florida bays and rivers.

Top to bottom: Threadfin herring (greenie), scaled sardine (whitebait) and Spanish sardine

In the springtime, scaled sardines (a.k.a. “whitebait” or “pilchard”) and threadfin herring (a.k.a. “greenback” or “greenie”) rank at the top of the list of Florida live baits.

The threadfin herring has a vibrant green back and prominent spots along the dorsal ridge. Most telling is the long, thread-like trailer extending from the anterior portion of the primary dorsal fin. The sardine lacks the dorsal trailer, has a noticeably larger eye, a light olive green back and scattered spots. (Spanish sardines sometimes mix with these— they'll be recognizable by their lack of back spots, and, as adults, their long, thin profile.)

Is it possible to tell them apart from afar?

Tampa Bay area guide Billy Miller says, “When you see bait on the flats running and making a commotion, those are the greenbacks. Whitebait will usually hang in one area. When you see bait ‘raining' on the surface, those are your greenbacks. Whitebait will just dimple the surface; you'll see one roll here, one there."

Scaled sardines typically remain inside bays and estuaries longer than threadfins of similar age. That means you'll often find the big whitebait on deeper flats, while locating sizable greenies requires a trip to the pass, beach or markers.

Bridges, like the Sunshine Skyway, see both bait species holding near the pilings. You'll see flashes in the water column and plenty of surface activity—particularly when mackerel or jacks find a school. Just remember the high-low thing.

“Scaled sardines typically hug the bottom and threadfins are typically toward the surface,” said St. Pete's Capt. Rob Gorta. “If you're in 20 feet and the bottom machine reads 15 feet, you know there's five feet of scaled sardines on the bottom. Threadfins will be suspended five to 10 feet below the surface.”

It's a full house.

Round 'Em Up

Over broad flats or on beach fronts, where bait schools often hug the shoreline contour, just idle until you spot a thick dark mass and sling the mesh “rodeo” style. For a more concentrated effort, set up on the edge of a grass flat and chum with moistened fish meal or tropical fish feed.

An old-school classic: Canned jack mackerel hand-mashed with wheat bread and just enough sea water to form a smelly paste. Flick fingernail-sized chunks downtide and once baitfish rise to gobble the chum, “walk” them into cast net range with progressively closer chumming.

Miller makes a key point: “Threadfins will not chum. If you see baitfish responding to your chumslick, that's whitebait. Once the whitebait gets excited, the threadfins will sometimes follow them.”

For cast netting livies, Capt. Jason Stock of Bradenton recommends a 1/4inch stretched mesh (measured corner to corner of a net square when diagonally stretched) for shallow flats, 3/8 around deep bridge sections and 1/2-inch for larger baits, deeper coastal waters and stronger current. Remember, the wider the mesh, the faster the net sinks.

Cast nets are most time-effective, but sabiki rigs, or any homemade gold-hook rig will tempt whitebait and greenies. This can be a good option when you're limited by wind, tide or cast net experience.

Dollar bill-sized threadfins make dandy offerings for tarpon, monster snook, sailfish and even offshore bullies like amberjack and grouper. Also, Gorta favors big threadfins for redfish cut bait because they release so much aroma that reds can track ‘em down even in dim conditions and murky water. Coastal sharks also dig cut greenies and don't think the mighty silver king won't stoop to scooping up a freshly cut half.

Whitebaits are the go-to choice for live baiting snook of common proportions, along with redfish, trout, cobia, small sharks and even tripletail. Baits of 2 to 4 inches fit the bill; smaller for tripletail, larger for sharks.

Hook either baits through the cartilage between the eyes and nostrils for fishing in current. In calm water, hide the hook beneath your bait by running it through the soft pocket right behind the pectoral fin joints. (This works equally well for free lining or floating baits under corks.)

If you've collected mostly greenies, it's inevitable a good number of them will expire in captivity. Skim dead ones out of the well and hold them on ice for snapper bait, or grind them with the day's leftovers into homemade chum blocks. FS

First Published Florida Sportsman Magazine April 2017

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