Forests could be key to estuarine fish conservation

Date:
November 4, 2021
Source:
Hokkaido University
Summary:
The diversity of threatened fish in estuaries increases when
surrounded by forest cover, whereas estuaries surrounded by farmland
show the opposite effect.



FULL STORY ==========================================================================
The diversity of threatened fish in estuaries increases when surrounded
by forest cover, whereas estuaries surrounded by farmland show the
opposite effect.


========================================================================== Estuaries -- areas where rivers meet the sea -- are one of the most
vulnerable ecosystems. They face anthropogenic threats, including
biodiversity loss and the collapse of natural fisheries. Determining
the factors contributing to the maintenance of estuarine biodiversity, especially that of fish, is vital for promoting estuarine conservation
and sustainable fisheries.

A team of scientists from Japan determined that the amount of forest and farmland surrounding rivers as they flow into the open sea impacts the
number of threatened fish species in Japan's estuaries. The finding,
published in the journal Conservation Biology, could help improve
estuary conservation and improve understanding of how to best develop
and maintain sustainable coastal fisheries. Involved in the study were
Dr. Edouard Lavergne and Professor Yoh Yamashita from Kyoto University,
and Professor Akihide Kasai from Hokkaido University.

"Understanding how human activities on land affect estuarine and coastal ecosystems through rivers has been a daunting task. This is because
many environmental and socioeconomic factors act in complex ways to
influence estuarine fish diversity as rivers flow into the open ocean,"
says Yamashita, a co-PI of the research team. "By collecting big data
on environmental, social, and land use factors and integrating it with
the results of environmental DNA analysis, we are the first in the world
to verify the general relationship between forests and estuarine fish
diversity over a wide area," adds Kasai, another co-PI.

The team used a method called environmental DNA metabarcoding, the
simultaneous identification of taxa present in a complex environmental
sample. They analyzed water samples, taken from 22 locations around Japan
where rivers flow into the sea, and looked for fish DNA. This fast and non-invasive approach is highly effective for assessing biodiversity in
aquatic ecosystems. Using it, the scientists identified 186 different
fish species, including 49 that are on Japan's red list of species facing varying degrees of threat.

The team also acquired data on water temperature and salinity, river
discharge, dissolved oxygen, pH, total nitrogen, and suspended solids.

Finally, they assessed watershed-scale land-use factors, how many people
live in each watershed, and how artificialized the coastline surrounding
the estuary and the riverbanks.

The team's statistical analyses showed that red-listed fish species were
richer in estuaries that were surrounded by higher forest cover. But
fish did worse in those waters surrounded by more agricultural land.

"Forests appear to play a more vital role in the conservation of fishes
at-risk than originally thought," says Kasai.

The researchers think this could be because forests retain water, thus protecting estuarine ecosystems from flooding and strong run-off after
heavy rain. They also prevent land erosion and runoff of fine sediments
that have serious harmful effects on aquatic ecosystems. Agricultural
land, however, can release fine sediments and pesticides into aquatic
systems.

The team says further research is needed to investigate how different
types of forest cover, such as natural unmaintained or planted forests,
affect these fragile ecosystems.

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


========================================================================== Journal Reference:
1. Lavergne Edouard, Kume Manabu, Ahn Hyojin, Henmi Yumi, Terashima
Yuki, Ye
Feng, Kameyama Satoshi, Kai Yoshiaki, Kadowaki Kohmei, Kobayashi
Shiho, Yamashita Yoh, Kasai Akihide. Effects of forest cover on
richness of threatened fish species in Japan. Conservation Biology,
2021; DOI: 10.1111/cobi.13849 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211104115052.htm

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