Scientists have developed a new eDNA analysis technique that could help conservationists target invasive fish populations before they become well-established.
The round goby fish, native to Eurasia, was accidentally introduced to the St. Lawrence River via ballast water from cargo ships in the 1990s.
In the decades since, the species has been rapidly colonizing the Great Lakes, competing with native species for food resources and eating the eggs of some game fish species.
These small fish easily camouflage themselves on the surface of muddy river and lake bottoms, making them hard to spot — especially when the invaders have only just arrived in a new body of water.
Spotting small numbers of goby fish before they can proliferate could help conservationists limit the ecological damage caused by the round goby.
In a new proof-of-principle study, published Tuesday in the journal Molecular Ecology, researchers at Cornell University showed eDNA analysis can be used to identify hard-to-spot goby populations, as well as gain insights into the scope of their invasion.
Previously, eDNA analysis efforts have been focused simply on the presence or non-presence of target species.
But the new genetic analysis techniques deployed by Cornell researchers promise more useful information.
“With these new advancements to eDNA methods, we can learn not only which invasive species are present in the environment, but because we identify the genetic diversity in the samples,” Kara Andres, first author of the new study, said in a press release.
“We can also predict how many individuals there are and possibly where they came from,” said Andres, a Cornell graduate student.
The latest research suggests scientists could use eDNA analysis to link the genetic signatures of invaders with the genomic signatures of known populations, potentially pinpointing the source of invasion.
For the proof-of-principle study, researchers used water samples from Cayuga Lake, one of New York’s Finger Lakes. The presence of the round goby was only recently identified in Cayuga Lake.
Before scientists proved the method’s effectiveness using real eDNA samples, they tested their eDNA technology using water-filled bins featuring one, three, five or 10 gobies. The scientists were able to match DNA in the water to the genes of the specific fish.
“We would be able to tell genetically if round gobies were introduced by ships from Europe, which is how they originally got to the Great Lakes, or by some other means of introduction. Knowing this information might be helpful if we hope to stem new introductions at early stages,” Andres said.
Levels of genetic diversity measured in eDNA samples could be used to gauge the success of a local invasions.
Low diversity levels would suggest an introduced species is struggling to adapt, while high levels of diversity would suggest rapid proliferation.
In Cayuga Lake, researchers identified genetic evidence of large numbers of round gobies, especially in the lake’s shallows.
“In the near future, this type of technique is likely to revolutionize how environmental and conservation management agencies monitor wild populations,” said co-author Jose Andrés, professor of ecology and molecular biology at Cornell.