Blackfin Tuna
Blackfin Tuna (Thunnus atlanticus) is a saltwater species. The first thing to check: dusky to black finlets along the back and belly in front of the tail — every other Atlantic tuna has yellow finlets. The look-alike to rule out is Yellowfin Tuna: yellowfin have bright yellow finlets with black edges, longer pectorals, and grow vastly larger.
Last updated
| Scientific name | Thunnus atlanticus |
|---|---|
| Also called | blackfin, deep bodied tunny |
| Water | Saltwater |
| Group | Tuna |
| Temperature | Prefers 70 to 82 °F and stays closer to shore than the larger tunas. |
How to identify a Blackfin Tuna
- Dusky to black finlets along the back and belly in front of the tail — every other Atlantic tuna has yellow finlets.
- Short pectoral fins that reach only to about the middle of the first dorsal fin.
- The smallest tuna in the Atlantic, with a dark blue-black back and a bronze-gold flank band.
If you would rather not work through a key on a wet deck, photograph the fish and let the app name it — you get the common and the scientific name back, and the record is filed before you release.
Fish it is mistaken for
| Species | How to tell them apart |
|---|---|
| Yellowfin Tuna | Yellowfin have bright yellow finlets with black edges, longer pectorals, and grow vastly larger. |
| Little Tunny | False albacore have wavy dark marks on the upper back and dark spots below the pectoral fin. |
Read the full entry for Yellowfin Tuna and Little Tunny.
Where it lives
Western Atlantic only, from Cape Cod to Brazil, concentrated around Florida, the Bahamas, the Gulf and the Caribbean. Found over reef edges, humps, wrecks and offshore structure.
Temperature
Prefers 70 to 82 °F and stays closer to shore than the larger tunas.
The conditions that matter
Blackfin hold on structure and edges and feed hardest at first and last light. Because they sit closer inshore than other tuna, current over a hump or wreck is often the deciding factor — the same spot is dead on slack and alive on a running tide.
Global Fishing League records 18 weather and water readings against every catch automatically — tide stage, barometric pressure, water temperature, salinity, dissolved oxygen, chlorophyll, swell, current, moon phase and more, taken at your GPS position at the moment you log the fish. Over a season that turns a hunch about blackfin tuna into a pattern you can read.
See every reading recorded with a catch, or the guides to what each reading means.
Size limits, bag limits and seasons
Size limits, bag limits, slot limits and seasons are set by your state wildlife agency — and for many offshore and migratory species by federal regulators — and on many waters they differ from the statewide rule. They also change between seasons. Check the current regulations for the exact water you are fishing before you keep a fish — we do not republish limits here, because a number that is a season out of date is worse than no number.
What the app does do is make your side of it accurate: every catch carries a length measured from the photograph, a GPS position and a timestamp, exportable if you ever need to show your work for a tournament or a record claim. It is also what a Global Fishing League entry is built from — a record that verifies itself, without publishing where you caught the fish.