Posted in | Ecosystems

Freshwater Fish are Facing a Catastrophic Decline

Image Credit: Shutterstock.com/ francesco de marco

Biodiversity in freshwater ecosystems is under severe threat, with up to one-third of freshwater fish species facing extinction, suggests a WWF report. 

A new report from the World Wide Fund (WWF)¹ is a wake-up call to governments worldwide, highlighting that human activities are severely impacting freshwater fish. 

The WWF has collaborated with 16 other conservation agencies, including the London Zoological Society (ZSL), Global Wildlife Conservation, and The Nature Conservancy, to produce 'The World's Forgotten Fishes,' a report which suggests that freshwater fish are under threat with up to a third of species facing extinction.

Whilst they only account for 1% of the Earth's surface freshwater areas rivers, lakes and wetlands represent the most densely biodiverse ecosystems on the planet. Stunningly these areas are home to almost a quarter of the world's vertebrates and 51% of the world's known fish species. 

There is much that researchers still don't know about these diverse freshwater species, but what is clear is the fact that they and the ecosystems they inhabit face an unprecedented crisis. Biodiversity is being lost in these regions twice as rapidly as similar losses are occurring in oceans and forests. 

Freshwater ecosystems support humanity too, the report suggests, with over 200 million people depending on freshwater fish as a food source. This industry provides jobs for 60 million individuals and has an estimated value of 38 billion USD. 

With one-third of these fish facing extinction, communities that rely upon them are at risk too. This is particularly true for the indigenous populations of poorer land-locked countries. 

The Fate of Freshwater Fish in Figures

The report reveals some disturbing figures that starkly illustrate the plight of freshwater fish. 

Over 80 species of freshwater fish have become extinct over the past fifty years, and more worryingly, this process seems to be accelerating with 16 of these extinctions occurring in the last 12 months alone. 

In most rivers populations of larger fish  —  those with masses above 30 kg  —  have already been completely decimated with those fish completely absent. The populations of species of mega-fish —  fish with masses in excess of 100 kg, like the Mekong giant catfish  —   face a similar fate with numbers already reduced by 94%. 

The population of 11,000 migratory freshwater fish species that migrate at some point in their lifecycle  —  including 5 species of shark  —  is down by 76% in comparison to counts conducted in 1970. 

Factors influencing this decline in freshwater fish populations include overfishing and damaging fishing practices, the introduction of invasive species, pollution, and climate change  —  all elements that disturb the delicate balance of these freshwater ecosystems. The report also points out that other threats such as microplastic pollution and anthropogenic noise are being discovered constantly.

The damage being done to these ecosystems represents something of a negative feedback loop for the creatures that exist within them. Whilst freshwater fish depend on a healthy freshwater ecosystem, these species fulfill an important regulatory role in maintaining the health of ecosystems with predatory species controlling populations of prey species and thus preserving a delicate balance and food webs in these regions2.

The Rescue Recovery Plan

The report prepared by the WWF and its collaborators doesn't just present the problems facing freshwater fish and their ecosystems. It also sets out a recovery plan designed to aid freshwater biodiversity.

The plan has been designed by scientists and experts in freshwater ecosystems, and it is based on six significant pillars. Every one of these has already been implemented in different regions across the globe.

These pillars are: 

  1. Allowing rivers to flow naturally 
  2. Improving water quality in freshwater ecosystems
  3. Protecting and restoring habitats
  4. Ending overfishing and sand mining  —  an under-reported cause of extreme environmental damage that supplies sand to the building industry
  5. Controlling the invasion of non-native species to ecosystems
  6. Protecting free-flowing rivers and removing old and obsolete dams

The report highlights 2021 as a year that represents world governments' last chance to implement changes that could mitigate the damage to freshwater ecosystems.

The WWF has already called upon the UK government to back its emergency recovery plan. Together with the 16 collaborative organizations that helped compile this report, they will urge other governments to undertake the steps it lays out in the report when they meet to discuss the destruction of Earth's biodiversity and natural habitats later this year. 

References

1. 'The World's Forgotten Fishes,' WWF, [2021], [https://europe.nxtbook.com/nxteu/wwfintl/freshwater_fishes_report/index.php#/p/1]

2. Vadas, R.L., [1990], ‘The importance of omnivory and predator regulation of prey in freshwater fish assemblages of North America,’ Environmental Biology, [https://doi.org/10.1007/BF00002747]

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Robert Lea

Written by

Robert Lea

Robert is a Freelance Science Journalist with a STEM BSc. He specializes in Physics, Space, Astronomy, Astrophysics, Quantum Physics, and SciComm. Robert is an ABSW member, and aWCSJ 2019 and IOP Fellow.

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