The Freshwater Fish Crisis
Freshwater represents the most threatened of all ecosystems. IUCN has prioritised freshwater fish in its Red List assessments: In the current IUCN Red List all 13 fish species listed as Extinct in the Wild and 76% of fish species listed as Critically Endangered are freshwater. This is a global problem, primarily due to habitat destruction from water pollution, damming and drainage of waterways, and the effects of invasive species.
Of the 5096 freshwater fish species assessed by the IUCN, 2506 are threatened, and 688 endangered, critically endangered or extinct in the wild. In the recent IUCN assessment in November 2011, it was stated:
‘The status of European freshwater flora and fauna is alarming with 37% of freshwater fish under threat.'
In comparison, only about 10% of the marine fish species assessed are threatened. Half of those, in fact, also spend part of their lives in freshwater.
For example, though once a common and widespread fish, the eight European species of sturgeon (Acipenser) have declined dramatically in range and numbers. Now, all but one of the eight European sturgeon species are Critically Endangered.
The four main causes of the decline in freshwater fish are pollution, damming and drainage of waterways, and the effects of invasive species.
- Pollution of waterways threatens 1748 species and caused 8 of the 13 global extinctions of European species. Both domestic and industrial pollution continues to be a problem worldwide.
- Wetland drainage or water abstraction (for agriculture, domestic or commercial use) threatens 737 species worldwide. It is the greatest threat in the driest countries, often ones that have many endemic species. It is the single biggest threat to European fishes ).
- Damming of waterways threatens 932 species worldwide. Many commercially important species are amongst the worst affected , such as salmonids and eels. There are Over 50,000 large dams worldwide, and are unfortunately very valuable to human infrastructure.
- Alien species are often introduced under government-sanctioned plans. 655 freshwater fish species are threatened by introduced alien species. These invaders affect residents in a variety of ways, such as competing for food, preying on them directly or introducing virulent diseases.
What has been done
Some measures have been taken to counteract this crisis. There have been practical measures, such as fish ladders on some dams, though they are often unsuitable. Tougher enforcement of water pollution regulations and tighter regulation of fish transport has also been implemented to some degree. The EU habitats directive has identified 26000 important natural sites for protection, in which some of the 202 threatened freshwater fish species are covered, but 60 species still have no protection.
Inside the Fish Ark at Morelia University © David J. Price/Plymouth Fishkeeper's Society
Some successful projects have helped to avoid likely extinctions:
Fish Lab at Morelia University in Mexico aims to maintain and breed the most threatened of Mexican live-bearing fishes, funded by Chester Zoo and hobbyists.
The Critically Endangered Azraq Killifish (Aphanius sirhani) from Jordan was rescued from extinction through measures taken by the Royal Society for the Conservation of Nature and Vienna Zoo . Holding spaces were created and a population monitoring programme carried out. The Azraq Killifish is now set to become the National fish of Jordan, and a viable wild population may be reinstated in the future.
However, many species are still in dire straits. For example, the Australian Southern Pygmy Perch (Nannoperca australis) exists in only a few small freshwater pools that are in imminent danger of being drained for vineyards.
More action is needed, and quickly:
Southern Pygmy Perch, Nannoperca australis
- More surveys: Gather baseline data of each habitat using standardised methodologies and training of in-country biologists.
- Detailed inventory: Create a full global inventory of freshwater fishes and threats to them, updating and completing the IUCN assessments (including the 1041 species for which there is too little data).
- Stop systematic alien introductions: by making them illegal, educating on the risks and develop eradication methods for already introduced species.
- Mitigate the effects of dams:
Remaining habitat of the Southern Pygmy Perch
Conduct accurate EIA prior to dam construction and ensure all new dams have appropriate fish passes and appropriate flow regimes. *Education and awareness: Teach locals about their unique aquatic biodiversity and use charismatic species as flagships for wetland conservation.
- Be prepared to rescue: Create facilities for rapid response to save species in peril and establish safety net ex-situ populations for those species that need it
More on what Fish Net and the ZSl are doing for freshwater fish.