Marine heatwaves could wipe out an extra six per cent of a country's
fish catches, costing millions their jobs

Date:
October 1, 2021
Source:
University of British Columbia
Summary:
Extremely hot years will wipe out hundreds of thousands of tons of
fish available for catch in a country's waters in this century, on
top of projected decreases to fish stocks from long-term climate
change, a new study predicts. Modelling a worst-case scenario
where no action is taken to mitigate greenhouse gas emissions they
projected a six per cent drop in the amount of potential catches
per year and 77 per cent of exploited species are projected to
decrease in biomass, or the amount of fish by weight in a given
area, due to extremely hot years. These decreases are on top of
those projected due to long-term decadal-scale climate change.

The study highlights the need to develop ways to deal with marine
temperature extremes, and soon, the researchers say.



FULL STORY ========================================================================== Extremely hot years will wipe out hundreds of thousands of tonnes of
fish available for catch in a country's waters in this century, on top
of projected decreases to fish stocks from long-term climate change,
a new UBC study projects.


========================================================================== Researchers from the UBC Institute for the Oceans and Fisheries (IOF)
used a complex model incorporating extreme annual ocean temperatures
in Exclusive Economic Zones, where the majority of global fish catches
occur, into climate- related projections for fish, fisheries and their dependent human communities.

Modelling a worst-case scenario where no action is taken to mitigate
greenhouse gas emissions they projected a six per cent drop in the amount
of potential catches per year and 77 per cent of exploited species are projected to decrease in biomass, or the amount of fish by weight in a
given area, due to extremely hot years. These decreases are on top of
those projected due to long-term decadal-scale climate change.

The numbers
* In Pacific Canada, Sockeye salmon catches are projected to decrease
by 26
per cent on average during a high temperature event between 2000 and
2050, an annual loss of 260 to 520 tonnes of fish. With losses due
to climate change, when a temperature extreme occurs in the 2050s,
the total decrease in annual catch would be more than 50 per cent
or 530 to 1060 tonnes of fish.

* Peruvian anchoveta catches are projected to decline by 34 per
cent during
an extreme high temperature event between 2000 and 2050, or more
than 900,000 tonnes per year. With climate change, a temperature
extreme is projected to cost Peruvian anchoveta fisheries more
than 1.5 million tonnes of their potential catch.

* Overall, a high temperature extreme event is projected to cause
a 25 per
cent drop in annual revenue for Peruvian anchoveta fisheries,
or a loss of around US$600 million
* Nearly three million jobs in the Indonesian fisheries-related
sector are
projected to be lost when a high temperature extreme occurs in
their waters between 2000 and 2050.

* Some stocks are projected to increase due to these extreme events,
and
climate change, but not enough to mitigate the losses
During extreme ocean temperature events and on top of projected
temperature changes each decade, researchers projected that fisheries'
revenues would be cut by an average of three per cent globally, and
employment by two percent; a potential loss of millions of jobs.

"These extreme annual temperatures will be an additional shock to an
overloaded system," said lead author Dr. William Cheung, professor and
director of UBC's Institute for the Oceans and Fisheries (IOF). "We see
that in the countries where fisheries are already weakened by long-term changes, like ocean warming and deoxygenation, adding the shock of
temperature extremes will exacerbate the impacts to a point that will
likely exceed the capacity for these fisheries to adapt. It's not unlike
how COVID-19 stresses the healthcare system by adding an extra burden."
Extreme temperature events are projected to occur more frequently in the future, says co-author Dr. Thomas Fro"licher, professor at the climate
and environmental physics division of the University of Bern. "Today's
marine heatwaves and their severe impacts on fisheries are bellwethers
of the future as these events are generating environmental conditions
that long-term global warming will not create for decades."


==========================================================================
Some areas will be worse hit than others, the researchers found,
including EEZs in the Indo-Pacific region, particularly waters around
South and Southeast Asia, and Pacific Islands; the Eastern Tropical
Pacific, and area which runs along the Pacific coast of the Americas;
and some countries in the West African region.

In Bangladesh, where fisheries-related sectors employ one-third of the country's workforce, an extreme marine heat event is expected to cut
two per cent -- about one million -- of the country's fisheries jobs,
in addition to the more than six million jobs that will be lost by 2050
due to long-term climate change.

The situation is similarly grim for Ecuador, where extreme high
temperature events are projected to adversely impact an additional 10
per cent, or around US$100 million, of the country's fisheries revenue
on top of the 25 per cent reduction expected by the mid-21st century.

"This study really highlights the need to develop ways to deal with
marine temperature extremes, and soon," Cheung said. "These temperature extremes are often difficult to predict in terms of when and where
they occur, particularly in the hot spots with limited capacity to
provide robust scientific predictions for their fisheries. We need to
consider that unpredictability when we plan for adaptations to long-term climate change." Cheung said that active fisheries management is
vital. Potential adaptations include adjusting catch quotas in years
when fish stocks are suffering from extreme temperature events, or,
in severe cases, shuttering fisheries so that stocks can rebuild. "We
need to have mechanisms in place to deal with it," said Cheung.

It will be important to work with those affected by such adaptation
options when developing them, as some decisions could exacerbate
impacts on communities' livelihoods, as well as food and nutrition
security, said co- author Dr. Colette Wabnitz, an IOF research
associate and lead scientist at the Stanford Center for Ocean
Solutions. "Stakeholders are diverse, and include not only industry,
but also Indigenous communities, small-scale fisheries and others. They
should be involved in discussions about the effects of climate change and marine heatwaves as well as the design and implementation of solutions." ========================================================================== Story Source: Materials provided by University_of_British_Columbia. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. William W. L. Cheung, Thomas L. Fro"licher, Vicky W. Y. Lam,
Muhammed A.

Oyinlola, Gabriel Reygondeau, U. Rashid Sumaila, Travis C. Tai,
Lydia C.

L. Teh, Colette C. C. Wabnitz. Marine high temperature extremes
amplify the impacts of climate change on fish and fisheries. Science
Advances, 2021; 7 (40) DOI: 10.1126/sciadv.abh0895 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211001152717.htm

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