A brand new method to
infer stream fish abundance
Interview with
Prof. Taal Levi
Prof. Taal Levi
is an Assistant Professor at Oregon State University and has one of the most
diverse research profiles that we’ve ever seen. His studies range from disease
ecology to seed dispersal across all sorts of environments, from the Amazon
Forest to Alaska. His main peculiarity is perhaps the use of empirical data to
address applied issues, such as wildlife overexploitation, overfishing, climate
change and anthropogenic impacts in general.
Now, one of his
projects is focusing on estimating stream fish abundance using quantification of
environmental DNA. Environmental DNA (or eDNA) is the technique of detecting DNA
found in the environment, like water, soil or even from stomach contents,
instead of trying to extract it directly from an individual.
Here he talks about
this interesting and important project (we know how important it is to have reliable
fish abundance measures for fishery management!):
Taal Levi: Detection
of environmental DNA using real-time qPCR or digital PCR is already being used
to identify species occurrence. But now we are testing its effectiveness to
infer species abundance.
Firstly, it is
necessary to design species-specific primers – so, you have to decide a species
focus. We are mostly using mitochondrial markers, such as COI (cytochrome
oxidase I). Then, you have to collect some water samples and amplify all the
DNA of the target fish you find there. Finally, you make a relation between the
concentration of DNA from your target and the species abundance.
FEME: What have you found
so far?
Taal Levi: We
already tested this method for two salmon species and for Eulachon (a smelt) in the state of Oregon. All of
them are very economically and culturally important. Actually, the Eulachon is
so important for the people in that region that the Oregon’s state name was
given because of how the indigenous called that fish, Ourigan. For these three species
the method seems very effective.
FEME: Is it possible to
test its efficacy? How?
Taal Levi: We
are testing it using different forms of counts. For the salmon species, we
counted the number of individuals entering the streams every day for two years.
For the Eulachon, we used a different approach, a mark-recapture abundance estimative.
FEME: What are the
advantages of using this methodology?
Taal Levi: Several!
One is the possibility of sampling more areas very fast, because the only thing
you need to do is collect water. The other is to be able to work with
endangered species - usually, doing research with endangered species is very
complex, and this method is very cost-effective.
Taal Levi: The
eDNA is very local and time specific, so you can only infer abundance from a
small area and for the last 1 or 2 days.
FEME: Do you think that
this technique can be applied in Brazilian streams?
