Hexbyte Glen Cove Marine heatwaves could have severe negative impacts on global fish stocks thumbnail

Hexbyte Glen Cove Marine heatwaves could have severe negative impacts on global fish stocks

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Marine heatwaves could wipe out an extra six per cent of a country’s fish catches, costing millions their jobs. Credit: Cassiano Psomas on Unsplash

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 where no action is taken to mitigate greenhouse gas emissions they projected a six percent drop in the amount of potential catches per year and 77 percent 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 percent 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 percent or 530 to 1060 tonnes of fish.
  • Peruvian anchoveta catches are projected to decline by 34 percent 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 percent 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 percent 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 Frölicher, 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 percent—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 percent, or around US$100 million, of the country’s fisheries revenue on top of the 25 percent 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 and marine heatwaves as well as the design and implementation of solutions.”



More information:
William W. L. Cheung et al, Marine high temperature extremes amplify the impacts of climate change on fish and fisheries, Science Advances (2021). DOI: 10.1126/sciadv.abh0895

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Hexbyte Glen Cove Sri Lanka's marine disaster worsens as environmental toll rises thumbnail

Hexbyte Glen Cove Sri Lanka’s marine disaster worsens as environmental toll rises

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Members of the Sri Lankan Navy work to remove debris washed ashore from the Singapore-registered container ship MV X-Press Pearl.

Damage to Sri Lanka’s marine environment from a sinking chemical ship is worse than feared, officials said Friday, as more dead turtles, dolphins and whales washed up on the island’s beaches.

As of Thursday, 130 have been found dead on the Indian Ocean’s beaches since the MV X-Press caught fire last month before partially sinking off the coast after two weeks ablaze.

Sri Lanka’s government believes they were killed by the hundreds of tonnes of chemicals and plastics leaking from the ship.

“At least six turtle carcasses washed up along the western coast on Thursday alone,” a wildlife official told AFP.

He said they had also received the first report of a shoal of reef fish dying at Hikkaduwa, a southern tourist resort area known for its rich coral reefs.

“So far we have collected the carcasses of 115 turtles, 15 dolphins and five whales,” the official said, asking not to be named.

They include a blue whale carcass found off the northern Jaffna peninsula, about 400 kilometres (250 miles) north of Colombo, last week.

Officials are awaiting the results of forensic reports, he said.

The Singapore-registered ship was known to be carrying 81 containers of hazardous chemicals, including 25 tonnes of nitric acid, when it caught fire.

Around 1,200 tonnes of tiny plastic pellets and other debris that blanketed beaches have been scooped up and are being stored in 45 .

Sri Lanka is seeking $40 million in damages from the ship’s operators X-Press Feeders.

Local police have launched a criminal probe against the ship’s captain, chief engineer, chief officer as well as its local agent.

Environmentalists are also suing the government and the owners for allegedly failing to prevent the disaster.

The Sri Lankan navy said meanwhile Friday that another on its way from Colombo to Singapore had reported an engine room fire and that one crew member was missing.

Around 200 ships and oil tankers sail past Sri Lanka every day on the busy routes between Asia, the Middle East and Europe. Many dock in Colombo, the biggest transhipment hub in South Asia.



© 2021 AFP

Citation:
Sri Lanka’s marine disaster worsens as environmental toll rises (2021, June 25)
retrieved 25 June 2021
from https://phys.org/news/2021-06-sri-lanka-marine-disaster-worsens.html

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Hexbyte Glen Cove Oahu marine protected areas offer limited protection of coral reef herbivorous fishes thumbnail

Hexbyte Glen Cove Oahu marine protected areas offer limited protection of coral reef herbivorous fishes

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A large parrotfish scrapes algae from a Hawaiian reef. Credit: Noam Altman-Kurosaki

Marine protected areas (MPAs) around Oʻahu do not adequately protect populations of herbivorous reef fishes that eat algae on coral reefs. That is the primary conclusion of a study published in Coral Reefs by researchers from the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST).

There are over 20 species of herbivorous fishes and ten species of herbivorous urchins commonly observed on Hawaiian reefs. These species eat algae that grows on reefs, a process called herbivory, that contributes to the resilience of coral reefs by preventing algae dominance that can lead to overgrowth of corals.

The team of researchers found that of the four marine protected areas around Oʻahu they assessed in the study, three did not provide biologically significant benefits for herbivorous populations compared to reefs outside the areas.

“Marine protected areas are a fishery management tool to limit or prevent fishing to help the recovery and maintenance of fish abundance and biomass inside the MPA,” said senior author Erik Franklin, Associate Research Professor at the Hawaiʻi Institute of Marine Biology in SOEST. “An effective MPA should lead to a considerably higher abundance and biomass of fishes inside the MPA boundaries that would otherwise be caught by fishers but that wasn’t what our study found.”

Other factors influencing the biomass of herbivorous fishes included habitat complexity and depth, suggesting that environmental characteristics of may have had a greater impact on herbivorous fish populations than MPA protection.

A large school of surgeonfishes swims over a shallow Hawaiian reef. Credit: Noam Altman-Kurosaki.

Importance for Hawaii

As part of the Sustainable Hawaiʻi Initiative, the State of Hawaiʻi’s Division of Aquatic Resources leads the Marine 30×30 Initiative, which committed to effectively manage Hawaii’s nearshore waters with 30 percent established as marine management areas by 2030. Currently, five percent of waters within state jurisdiction, which is within three nautical miles of shore, have some form of marine management, but no-take MPAs that ban fishing only make up less than one-half of one percent of the nearshore waters. To attain the stated goal of the 30×30 Initiative would require an expansion of marine managed areas to include an additional 25 percent of Hawaiʻi state waters.

“Our results suggest that prior to an expansion of MPAs in Hawaiian waters, more effort should be directed to effectively manage the existing MPAs to see if they meet the desired management objectives,” said lead author and UH Mānoa’s Marine Biology Graduate Program graduate student Noam Altman-Kurosaki. “The addition of more MPAs throughout the state that have similar performance to the Oʻahu MPAs would just lead to a series of paper parks that don’t provide biologically significant conservation benefits while decreasing fishing opportunities.”

Study details

Franklin said the research resulted in a comparative analysis of herbivorous fish and urchin populations inside and outside of Oʻahu MPAs that demonstrated biologically insignificant differences in fish biomass between the MPAs and reference areas, except for one site, Hanauma Bay. The analyses used statistical methods to assess the effects of protecting population within MPAs and the influence that differences in benthic habitats contributed to the results.



More information:
Noam T. Altman-Kurosaki et al, O’ahu’s marine protected areas have limited success in protecting coral reef herbivores, Coral Reefs (2021). DOI: 10.1007/s00338-021-02054-5

Citation:
Oahu marine protected areas offer limited protection of coral reef herbivorous fishes (2021, February 27)
retrieved 28 February 2021
from https://phys.org/news/2021-02-oahu-marine-areas-limited-coral.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information pu

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