A new study shows that the plot of Finding Nemo might have a slim basis in science. Upon young Nemo's capture by Australian scuba divers at the start of the film, his helicopter father Marlin embarks on a days-long search for his son, befriending sharks and escaping the belly of a whale along the way.
While the adult Marlin is the one to swim great distances in the Disney/Pixar film, researchers have found that clownfish sometimes travel hundreds of kilometers across the open ocean. But it's the babies, not fully grown clownfish, that make these journeys.
Steve Simpson of the University of Exeter worked with colleagues from the Australian Research Council Centre of Excellence for Coral Reef Studies, Sultan Qaboos University, and the Centre National de la Recherche Scientifique in France to examine the dispersal of Omani clownfish larvae. The team's findings were published in the journal PLOS ONE this week.
Genetic particularities helped researchers identify which clownfish were locals, which ones were long-distant migrants, and which ones were hybrids. Dr. Simpson led a group of 24 undergraduate and postgraduate students from the University of Edinburgh to the southern coast of Oman, where they clipped small samples from the fins of 400 clownfish before releasing them back into the ocean. They then used these DNA fingerprints to track migration patterns between coral reef systems in the area.
It turns out that there is a significant exchange of offspring happening between two clownfish populations separated by 400 kilometers of surf beach on the coast. The study found that six percent of fish sampled had migrated the nearly 250 miles to reach the other group.
The clownfish are only about a week old at the time of their journey. After settling down in one coral reef, clownfish are known to spend the rest of their lives in the shelter of host anemones, making the infants' travels appear that much more incredible.
Even Marlin's ride on the East Australian Current with a crew of mellow sea turtles has some truth to it. It appears the clownfish larvae get some help by finding faster flows of water.
"When they arrive at the reef, they are less than a centimeter long, and only a few days old," Simpson said in a press release. "So to travel hundreds of kilometers they must be riding ocean currents to assist their migration."
Researchers also determined that second-generation hybrids existed in both populations, suggesting that travelers found mates in their new neighborhood and reproduced.
"This study is the furthest anyone has tracked the dispersal of coral reef fish, and it demonstrates that distant populations in the marine environment can be well connected," said Simpson.
Simpson said that understanding the relationships of different populations and the dispersal patterns of fish larvae will allow for better protection of sensitive marine populations, because marine scientists can then design coherent networks of protected areas.