Scientists used to think that when baby fish (called larvae) hatched, they
floated in the plankton to wherever currents take them. Recently, scientists have actually measured how far larvae disperse, and it turns out, they almost never settle far from home! The scientists who did this research began to wonder, maybe larvae are really strong swimmers. If this was true, then larvae could fight the currents so they stayed close to their home reef, or could return after being carried away by currents.
The scientists tested this by putting larvae on fish treadmills, called flumes.
They collected Elacatinus lori larvae as they hatched on the reef in Belize, Central America, and raised them in a wet laboratory on the island of South Water Caye (put in picture of lab). As the larvae developed, scientists put them in the flume and measured how long they could swim at different water current speeds. They found that E. lori larvae actually can’t swim long at all! When scientists tested larvae at speeds close to the current speeds on the reef, larvae can’t swim longer than a few minutes. What a discovery!
Now the scientists are wondering how these tiny larvae, who can barely swim, are settling so close to their home reefs. Stay tuned as scientists test their next question: maybe these larvae are skilled navigators? This summer the scientists will test the orientation abilities of larvae, as nobody before ever has. Eventually, their research will help answer the question of how larvae disperse. Once we know that, we can make marine protected areas that keep of our fish and our oceans healthy.