Predicting tropical fish patterns in Japan

Date:
March 10, 2022
Source:
Hokkaido University
Summary:
Scientists have developed a model that predicts six tropical
fish species will expand into northern parts of Japan as sea
temperatures rise.



FULL STORY ========================================================================== Scientists have developed a model that predicts six tropical fish species
will expand into northern parts of Japan as sea temperatures rise.


==========================================================================
A new study forecasts how global climate change will affect tropical
fish species in Japan. The research, published in the journal Frontiers
in Built Environment, predicts that six tropical fish species will
expand northward into temperate regions of the Japanese coast as sea temperatures rise.

Climate change is causing temperate coastal waters to get warmer,
affecting the abundance, distribution and types of marine species that
live there. In Japan, water temperature in coastal regions has risen
by 1.16DEGC degrees over the last 100 years, which is twice the global
average of 0.56DEGC degrees.

Tropicalization -- the increase in species originating from tropical
waters - - will affect humans in many ways. For example, rising numbers
of toxic harmful species can be detrimental for fisheries and leisure, increasing the risk of food poisoning or injuries when swimming. Increases
in herbivorous fish can lead to loss of seagrass and seaweed beds,
reducing carbon uptake. On the other hand, rising numbers of tropical
reef fish can attract tourism and provide opportunities for the aquarium
fish trade and environmental education.

"Our current knowledge of how marine ecosystems in Asia will respond to
climate change is limited, especially for coastal fish species," explains
Kenji Sudo, marine ecologist at Hokkaido University. "We developed
a model to investigate how tropical fish in Japan might respond to
changing environmental conditions." The Hokkaido researchers selected
six tropical fish species from the 4,500 species of fish that inhabit
Japanese waters. They chose species that represent a range of different
effects on humans and have well-documented numbers. They studied two toxic harmful fish (Aluterus scriptus and Scarus ovifrons), two herbivorous fish (Kyphosus bigibbus and Siganus fuscescens), and two tropical reef fish (Amphiprion frenatus and Chaetodon auriga).

The researchers used publicly available distribution data and numerical
models to estimate how the six species' future habitats might change
under different climate change scenarios. They examined how different environmental variables, such as minimum sea surface temperature, depth,
slope, coral reef area, and seagrass/seabed areas, affect fish species
patterns and used this information to predict future changes.

They found that the minimum sea surface temperature was the most important factor affecting distribution patterns for all species. Depth, slope
and seagrass/seaweed beds were also important for some species.

The model showed that, under two different carbon emission scenarios,
all six tropical species were predicted to expand into the middle to
northern parts of Japan. By the 2090s, their habitat range was estimated
to expand to around 1.5 times that of 2000-2018 with severe warming. The expansion was predicted to be highest along the Pacific coast, which
is affected by the warm Kuroshio and Tsushima Currents along the coast
of the Sea of Japan. However, the model indicated that habitat range
changes could be minimised by stringent mitigation measures.

"The results indicate that many human activities along the Japanese
coasts, such as fisheries, leisure use and human health may be greatly
affected by changes in tropical fish patterns without proper mitigation measures against climate change," says co-author Masahiko Fujii,
Associate Professor at the Faculty of Environmental Earth Science,
Hokkaido University.

The study suggests that ambitious commitment to reducing greenhouse gas emissions could prevent future tropicalization. The model could be used
by local decision makers to plan suitable climate adaption programs.


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


========================================================================== Related Multimedia:
* Fish_species_selected_for_this_study ========================================================================== Journal Reference:
1. Kenji Sudo, Serina Maehara, Masahiro Nakaoka, Masahiko
Fujii. Predicting
Future Shifts in the Distribution of Tropicalization Indicator
Fish that Affect Coastal Ecosystem Services of Japan. Frontiers
in Built Environment, 2022; 7 DOI: 10.3389/fbuil.2021.788700 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220310115142.htm

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