On The Line

Where exactly do Gulf and Atlantic waters converge?

FSF Staff September 4, 2013

I’m trailering my boat to Key West in preparation of a Dry Tortugas trip and want to make sure I abide by all of the species and gear regulations. How do I know whether or not I am fishing Atlantic or Gulf waters? – John Friedman

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Chart: NOAA

Determining whether you are fishing in the Gulf or Atlantic is fairly obvious for the most part, but there are times when it can be puzzling. Driving south from Florida’s mainland, you’ll thoroughly enjoy the natural beauty of one of the world’s greatest road trips. Once you have officially entered Monroe County, Gulf and Atlantic waters are clearly separated by the engineering marvel known as Overseas Highway. Where
the scenic road trip ends in Key West is where things get confusing.

Before we go any further we must first review some basic geography terms all mariners should be familiar with. The earth is divided by meridians and parallels, which are imaginary lines used as reference points to measure distance. Evenly spaced circles of latitude are called parallels and run east to west. The equator is the most famous parallel of latitude. Meridians run north to south and are perpendicular to circles of latitude.

As defined by the South Atlantic and Gulf of Mexico Fisheries Management Councils, the Atlantic Ocean covers all state and federal waters south and east of the boundary line created at the intersection of the outermost edge of the Exclusive Economic Zone and 83°00′ W longitude. This invisible line separating Gulf and Atlantic waters continues north along the meridian of 83°00′ W to its point of intersection at 24°35′ N latitude. From this point, near the Dry Tortugas, the parallel continues east through Rebecca Shoal to 82°13′ W longitude. Now follow the territorial sea boundary south and east to the intersecting point of 24°33′ N latitude and continue along this parallel to Key West.

While the numbers alone are difficult to interpret, a quick glance at a nautical chart will clear up some of the ambiguity. Ignorance is not a valid excuse for fishery violations and it’s important you have a clear understanding of the waters you are fishing. With the line going through prime bottom fishing territory around Rebecca Shoal, there could be times when you’re very close to the border or jockeying from one side to the other in search of prized grouper and snapper. The boundary also runs through the southernmost edge of the Marquesas Keys, but anglers targeting bonefish, tarpon and permit don’t have to worry since regulations for these prized three are corresponding.

Depending on your chartplotter and the type of chip you have installed, your unit may display the dividing line for the two waters. If not, you should be able to set a boundary line or security zone on your chartplotter. This type of charting function will also benefit anglers in the event they are fishing a tournament with limiting boundaries. If you have an outdated plotter you could simply keep a close eye on your GPS coordinates. When bottom fishing west of the Marquesas Keys know that if you cross 24°35′ N latitude or 83°00′ W longitude you have entered Gulf waters.

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