One of the more variable factors with which plants and animals must contend in the St. Johns River is salinity, or salt concentration in the water.

It’s generally considered to be the most unpredictable section, thanks to its marshy, swampy waters. This portion of the river is freshwater. Indian River County is where the river begins as a network of marshes, at a point west of Vero Beach aptly named the St. Johns Marsh in central Florida. Lake George is evdently an interesting body of water which reportedly has a very flat botton and is only about 10 feet deep. This means that due to its groundwater and marsh beginnings, the River is predominately fresh water. Its tranquil, idyllic setting in north central Florida offers anglers great fishing opportunities in a peaceful setting. As it winds its way towards Titusville, where the Upper Basin ends, the river widens and becomes extremely fishable.

Fresh and salt water fish species inhabit the lake and will locate near suitable water salinity acceptable to them. It is measured in parts per thousand (ppt), or practical salinity units (psu), or it can be calculated from measuring the electrical conductivity of a water sample. The St. Johns River is a blackwater stream, meaning that it is fed primarily by swamps and marshes lying beneath it; water seeps through the sandy soil and collects in a slight valley. Salinity is a measure of the amount of salt that is dissolved in a sample of water. The St. Johns River begins as a network of marshes, consolidating into a blackwater stream.

The St. Johns River is one of the best freshwater fishing spots in Florida. When ocean waters receded and uncovered the central landmass that is now Florida some 10,000 years ago, residual seawater became trapped in pockets of what is now our aquifer. Freshwater fishing tops saltwater fishing for many reasons.

It’s not until the River hits the Jacksonville area that the water becomes brackish. On average, salinity ranges from about 35 parts per thousand at the ocean (full strength seawater) to about 10-18 ppt near downtown Jacksonville (brackish water), and 0-5 ppt near the Buc… St. Johns’ Upper Basin begins just west of Vero Beach. Not all freshwater is really “fresh,” and the St. Johns River is no exception.

Florida’s springs tend to have more salt and minerals in their water than others. North of Palatka the St. Johns is predominately salt (brackish) water. This 60-mile stretch of the St. Johns River is the southernmost headwaters where the tannin-stained river originates out of the vast marshes, swamps, water management areas and canal systems. The beauty of the St. Johns River is that you have no idea what you might catch. There are plenty of saltwater fish in the river and its lakes.