UTERFlorida has four snook species: common snook, fat snook, tarpon snook and swordspine snook. Almost every snook you catch on a beach, pass, dock light or mangrove point is a common snook. It's the big one, with adults topping 40 inches. The other three are small fish, mostly 10 to 20 inches, that live in the brackish creeks, canals and rivers of South Florida, especially on the Atlantic side. Four features tell them apart: the anal fin, the pelvic fins, the body depth and the size of the scales.
Quick-ID table
| Feature | Common snook | Fat snook | Tarpon snook | Swordspine snook |
|---|---|---|---|---|
| Anal fin soft rays | 6 | 6 | 7 (the only one) | 6 |
| Anal spines | Relatively short; the laid-back fin falls short of the tail base | Moderate | Moderate | Very long second spine; the laid-back fin reaches past the tail base |
| Pelvic fins | Don't reach the vent | Reach to or past the vent | Tips reach past the vent | - |
| Body | Long and fairly slim, with a sloped head and a jutting lower jaw | Deep for its length, not flattened | Compressed (tarpon-like) with a strongly upturned lower jaw | Slim; the smallest snook, with a slightly concave head profile |
| Scales | Medium | Small (the most scales along the side) | Medium | The largest of any snook |
| Mouth | Large | Reaches to below the center of the eye | Upturned | Medium |
| Typical size | Adults past 47 inches total length | About 10 inches, up to about 28 | About 15 inches, up to about 22 | About 10 inches, up to about 15 |
| Where in Florida | Both coasts; Cape Canaveral to the Keys and up the Gulf to Cedar Key | Mangroves; more often in fresh water than common snook | Coastal and often fresh water; rare on the west coast | Slightly brackish to fresh water; rare on the west coast |
Features are from FWC's snook profiles, the Florida Museum and Fishes of Texas. All four have the black lateral line running onto the tail that gives the "linesider" its name, so that line won't separate them.
The features in detail
Count the anal fin rays
The anal fin is the small fin on the belly just ahead of the tail. It has three hard spines in front, then soft, branched rays. Spread it and count the soft rays. If you count seven, FWC calls it a tarpon snook, the only one with seven. Six means one of the other three. Common snook rarely show five or seven, so use the jaw and body shape to confirm.
Lay the anal fin back
Fold the anal fin flat against the body. On a swordspine snook it reaches past the base of the tail. Its second spine is the long "sword" that gives the fish its name. On a common snook, the Florida Museum describes the anal spines as relatively short, and the folded fin falls short of the tail base.
Check the pelvic fins against the vent
The pelvic fins are the paired fins under the chest. Lay them back and see where the tips land compared with the vent (the anus). On a common snook they fall short. On a fat snook they reach it or pass it, and on a tarpon snook FWC says the tips reach beyond it. This is the quickest check between a small common snook and a fat snook.
Body depth and the jaw
A fat snook looks chunky, deep in the body for its length but not flattened, and its mouth reaches back under the middle of the eye. A tarpon snook looks flattened side to side, like a little tarpon, with a lower jaw that sweeps up. A common snook is the long, sloped-head fish with a lower jaw that juts forward.
Scales
Swordspine snook have the biggest scales of the four. Fat snook have the smallest, so more of them fit along the side. On a phone photo in good light the difference shows, but it's the hardest feature to judge without a fish of the other kind next to it.
Where you'll find each one
- Common snook are the fish of Tampa Bay, Charlotte Harbor, Palm Beach and the Treasure Coast, the Space Coast lagoons and Biscayne Bay. They use beaches and passes in summer and back up into rivers, canals and residential creeks when the water cools. See our snook fishing by season guide.
- Fat, tarpon and swordspine snook are mostly fish of the southeast Florida coast: canals, spillways, tidal creeks and freshwater rivers. Mangrove shorelines are their nursery. FWC lists tarpon and swordspine snook as rare on the west coast. If you catch a small, odd-looking snook in a Palm Beach or Stuart canal, it's worth a second look.
A two-minute check on the boat
You don't need a lab. For any snook under about 20 inches from a South Florida canal, creek or river, run this order:
- Anal fin. Spread it and count the soft rays behind the spines. Seven means a tarpon snook. Six means keep going.
- Fold it back. If the anal fin reaches past the base of the tail, it's a swordspine snook.
- Pelvic fins. Lay them back. Short of the vent points to common snook. Reaching the vent or past it, on a deep-bodied fish, points to fat snook.
- Jaw and body. An upturned jaw on a flattened body backs up tarpon snook. A chunky body with a mouth reaching under the middle of the eye backs up fat snook.
- Photo. Shoot the spread fins and the head, then let it go.
For anything over about 28 inches, you can skip the count. FWC's size ranges put the three smaller species well under that, so a fish that size is a common snook.
Mistakes we see most
- Calling every small snook a "fat snook." Anglers often use "fat snook" for any chunky small fish. Most of those are young common snook. Check the pelvic fins.
- Counting the spines as rays. The anal fin has three hard spines up front. Count only the soft rays behind them.
- Using the lateral line. All four have the black lateral line onto the tail, so it can't separate them.
Why it matters: the snook rules
Florida's snook rules are among the strictest for any inshore fish. Closed seasons and slot limits differ across nine management regions, and the Gulf and Atlantic sides don't follow the same calendar. Keeping a snook also takes a snook permit on top of a saltwater license. FWC's rules are written for "snook," and its snook page lists all four species, so a fat or tarpon snook isn't a loophole. We don't print the numbers here because they change, sometimes in the middle of a season. Check before you keep one:
- Florida: FWC snook regulations, and measure total length per FWC's measurement guide
- Texas (common snook turn up on the southern Texas coast): Texas Parks and Wildlife saltwater rules
If you catch an unusual snook, FWC's snook research program studies the species closely, and a good photo with a date and location on iNaturalist helps document where the rarer three turn up.
Photographing a snook for ID
Support a big snook horizontally under the belly rather than hanging it by the jaw. For ID, lay the fish flat with the anal and pelvic fins spread in one side-on shot, and take a second shot of the head, side on, to show the jaw. More tips in how to identify a fish from a photo.
What Fish Scouter's Fish ID will tell you
Fish Scouter's species book carries one snook entry, the common snook, because it's the one anglers target. Fish ID reads the marks it used and how sure it is. If a photo looks like one of the smaller three, Fish ID will say the true species may not be in its book and name the closest match. That's your cue to count the anal rays. The snook card has the season for your water, the baits that work and a link to the current FWC rule. Try Fish Scouter free.