Lionfish Shown to Tolerate Freshwater

The effects of the lionfish invasion currently ongoing in Florida and surrounding waters look worse and worse each day, as research continuously reveals just how much damage the fish are causing on native fish populations. But the story has taken a new plot twist, as a child’s science fair project and subsequent scientific articles have revealed that the lionfish, much like bull sharks, can tolerate freshwater environments giving them a whole new environment to invade.

In a recent Sun Sentinel article, a 12-year old student from Jupiter, Florida, showed that lionfish could survive in water with salt concentrations as low as 6 parts per thousand. Normal ocean salinity is around 35ppt, though inshore waters tend to fluctuate with rainfall and other factors. Lauren Arrington’s experiment included five aquariums which had their salinities slowly dropped while monitoring the condition of the resident fish. A sixth aquarium was left at normal salinity as a control tank. Over a two week period, the salinity of each tank was taken down to 6ppt, which is where the experiment was stopped because Lauren didn’t want the fish to die, which would disqualify her from the science fair competition. At 6ppt, the seemed to be completely unaffected.

Lauren went on to win third place in the zoology division of the Palm Beach County regional science and engineering fair, but her project landed her a mention on a scientific paper, something we doubt the first and second place winners ever got.

Craig Layman, an ecology professor at North Carolina State University, built off of Lauren’s project by conducting their own study, which was published this year in the Environmental Biology of Fishes. Layman and his team of students took the salinity all the way down to zero, revealing that lionfish could tolerate a minimum salinity of 5ppt and even withstand influxes of freshwater.

So how does this add to the lionfish’s devastating effect? Well, a lot of marine fish use freshwater systems as nurseries for their young. They travel up into rivers and estuaries to lay eggs, and the juvenile fish live in these protected areas until they are big and mature enough to fend for themselves. With the lionfish present, however, these juvenile fish are likely to get annihilated, further affecting native fish species in a big way.