'Environmental DNA' Helps Scientists in Monitoring Fish Migration

Researchers from the Rockefeller University have successfully recorded the migration of several key fish species with the use of "Environmental DNA" strained from water samples.

Their new method of recording fish migration, described in a paper published in the journal PLOS One, was made possible by the vast knowledge they have gained from fish migration studies conducted over many years with fishnet trawls. However, eDNA offers a new monitoring system that only involves fraction of the effort and cost of trawling, all without harming the fish.

"By conducting a series of tests over time, collecting surface water from the same point on both the Hudson and East Rivers once a week for six months, we've successfully demonstrated a novel way to record fish migration," said Mark Stoeckle, senior research associate at Rockefeller University and lead author of the study, in a press release.

For the study, the researchers collected one liter of water samples from New York's East and Hudson Rivers for six months. They then strained eDNA from the water samples. Fish leave behind traces of their DNA as they swim. The researchers noted that the DNA left behind by the fish was durable enough to withstand the currents and tides of the river.

Overall, the researchers obtained the DNA of 42 fishes. Out of those, 81 percent belongs to species known to be locally abundant or common, while 23 percent belongs to uncommon ones.

The researchers used the weekly eDNA data they gathered from the rivers to create a moving picture of fish migration in the area. They observed nothing significant in the fish migration pattern they created using the eDNA. There's also no significant change in seasonal movements and the species of fish found.

Nevertheless, the success of the eDNA and the similarities of its result to previous fish migration monitoring methods only shows that it can effectively used as proxy for monitoring fish migration.

"It amazes me that we can get the same information from a small cup of water and a large net full of fish," added Dr. Stoeckle.