PALATKA, Fla., May 14, 2019 ― The St. Johns River Water Management District Governing Board today approved $450,000 in funding for gizzard shad harvesting from Lake George, part of the St. Johns River system in Putnam and Volusia counties. Because removing large numbers of shad from a water body removes the nutrients contained in the fishes’ bodies, the harvest will help improve water quality in the lake by removing an estimated 4,940 pounds of phosphorus.
“Gizzard shad removal is especially relevant now as we look to move forward with turnkey projects to improve water quality, as directed by Gov. DeSantis, and as Lake George and the lower St. Johns River are currently experiencing algal blooms,” said St. Johns River Water Management District Executive Director Dr. Ann Shortelle. “Rough fish harvesting is both effective — with proven results in Lake Apopka and Lake Griffin — and cost-effective due to combined public-private financing of these types of projects.”
Water quality data from Lake George suggest the reduction in phosphorus recycling caused by shad removal is roughly seven times the direct phosphorus removal benefit. District shad harvests on Lake George between 2013 and 2018 removed more than 5 million pounds of fish containing a total of 22,312 pounds of phosphorus.
Gizzard shad are a native fish found in most Florida waters and account for 5 to 20 percent of the total fish population in healthy Florida lakes. However, in nutrient-rich, algae-dominated lakes, gizzard shad proliferate and can account for more than 90 percent of the total fish population.
Gizzard shad feed on algae on the lake’s bottom, stirring up sediments and clouding the water. Shad excrete nutrients back into the water, recycling nutrients from the bottom that can feed more algae in the water. Thus, by removing these fish, additional nutrients will not be recycled into the lake to impair its water quality.
Harvesting gizzard shad from Lake George is conducted during warmer months to avoid potentially catching untargeted species, including American shad, a species that is managed and protected under the Atlantic States Marine Fisheries Commission.
The district hires commercial fishing vendors to net gizzard shad. Sport fish caught in nets during the harvests are immediately released. The program is closely monitored and permitted by the Florida Fish and Wildlife Conservation Commission.