Does DNA in the water tell us how many fish are there?

Date:
July 3, 2020
Source:
National Institute for Environmental Studies
Summary:
Researchers have developed a new non-invasive method to count
individual fish by measuring the concentration of environmental DNA
in the water, which could be applied for quantitative monitoring
of aquatic ecosystems.



FULL STORY ========================================================================== River water, lake water, and seawater contain DNA belonging to organisms
such as animals and plants. Ecologists have begun to actively analyze
such DNA molecules, called environmental DNA, to assess the distribution
of macro- organisms. Challenges yet remain, however, in quantitative applications of environmental DNA.


==========================================================================
In a research article published online in Molecular Ecology, researchers
from the National Institute for Environmental Studies, Tohoku University, Shimane University, Kyoto University, Hokkaido University, and Kobe
University, have reported a new method for estimating population abundance
of fish species (or more generally, a target aquatic species), by means
of measuring concentration of environmental DNA in the water. Their
results suggest the potential of the proposed approach for quantitative, non-invasive monitoring of aquatic ecosystems.

DNA molecules are released from organisms present, are transported by
the flow of water, and are eventually degraded. In a natural environment,
these processes can operate in a complex way.

"This complicates and limits the traditional approach of population quantification based on environmental DNA where the presence of a
definite relationship between the concentration of environmental DNA
and population abundance has been critical, "explained Keiichi Fukaya,
research associate at the National Institute for Environmental Studies
and the lead author of the paper.

"We thought that these fundamental processes of environmental DNA,
the shedding, transport, and degradation, should be accounted for,
when we estimate population abundance through environmental DNA," he said.

The authors implemented this idea by adopting a numerical hydrodynamic
model that explicitly accounts for the processes to simulate the
distribution of environmental DNA concentrations within an aquatic
area. "By solving this model in the 'inverse direction', we can
estimate fish population abundance based on the observed distribution
of environmental DNA concentrations," Fukaya explained.

A case study conducted in Maizuru Bay, Japan, confirmed that the
estimate of the population abundance of Japanese jack mackerel (Trachurus japonicus), obtained by the proposed method, was comparable to that of
a quantitative echo sounder method.

"The idea and framework presented in this study forms a cornerstone
towards quantitative monitoring of ecosystems through environmental DNA analysis. By combining field observation, techniques of molecular biology,
and mathematical/ statistical modeling, the scope of the environmental
DNA analysis will be broadened beyond the determination of the presence
or absence of target species," explained Professor Michio Kondoh from
Tohoku University, who led the 5.5-year environmental DNA research
project, funded by the Japan Science and Technology Agency (CREST).

This work was supported by JST CREST Grant Number JPMJCR13A2, Japan.


========================================================================== Story Source: Materials provided by National_Institute_for_Environmental_Studies. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Keiichi Fukaya, Hiroaki Murakami, Seokjin Yoon, Kenji Minami, Yutaka
Osada, Satoshi Yamamoto, Reiji Masuda, Akihide Kasai, Kazushi
Miyashita, Toshifumi Minamoto, Michio Kondoh. Estimating
fish population abundance by integrating quantitative data on
environmental DNA and hydrodynamic modeling. Molecular Ecology,
2020; DOI: 10.1111/mec.15530 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200703094920.htm

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