Latest news with #freshwaterfish
Mail & Guardian
13-07-2025
- Science
- Mail & Guardian
Africa's freshwater fish crisis: 26% of species threatened with extinction
Clanwilliam sand fish: Supplied: Jeremy Shelton From the tiny They are found in sediment-rich rivers, shallow ponds, the great lakes, caves, canyons, mountain streams and forests. Yet they are This is according to a The report reveals that 26% of Africa's assessed freshwater fish species are threatened with extinction, but there are large data gaps so the true number is likely to be much higher. Africa is a global hotspot of freshwater fish diversity, home to more than 3 200 species — more than a quarter of the world's total freshwater fish. It's also a 'hotspot of risk', said Eric Oyare, the freshwater lead for WWF Africa. 'When these fish disappear, we lose much more than species: we lose food security, livelihoods, ecosystem balance, and resilience to floods and droughts. These declines are a red flag for the broader health of Africa's freshwater ecosystems, which are the very life support systems for people and nature.' But these lifelines are collapsing under the weight of multiple threats. These include habitat Freshwater fish populations are in freefall across the continent. In the Zambezi floodplain, When people think of the continent's biodiversity, few consider Africa's astonishing diversity of freshwater fish, 'yet they have swum through the continent's communities and cultures for millennia, and are still critical to the daily lives of tens of millions of people — as well as to the overall health of their freshwater ecosystems', said the report. Africa's rivers, lakes and wetlands are home to at least 3 281 freshwater fish species — a figure that includes Madagascar and 'that is almost certainly a significant underestimate'. This is because so many species have not yet been described by science and new species are being discovered in Africa every year — 28 during last year alone. These fish are vital for people and nature, supporting ecosystem functionality and the provision of ecosystem services across the continent, enhancing food security and nutrition for millions. They support countless livelihoods, particularly in vulnerable communities and landlocked countries. More than three million tonnes of freshwater fish are caught each year on the continent, representing nearly 30% of the reported global freshwater fish catch. This figure, too, 'is 'definitely a major underestimate', the report said, again because of a lack of data, especially for small-scale fisheries. The continent boasts 12 of the top 25 inland fish producing countries in the world, with Uganda coming in highest in sixth place. The annual catch feeds the highest per capita consumption of freshwater fish of any continent in the world and employs more than three million people. It plays a central role in the cultures of many indigenous peoples. And some fishes are economically important either as the lure for recreational anglers or as dazzling aquarium fishes. Weird and wonderful The continent's freshwater fish are much more than just food or economic resources. The report cited how possibly the most famous of Africa's freshwater fishes are the incredibly diverse cichlids, with at least 1 600 endemic species found in the Great Lakes – Victoria, Tanganyika, and Malawi. 'These cichlids are one of the most spectacular examples of speciation in the world and provide scientists with a unique opportunity to better understand the drivers of species evolution.' Livingstone's cichlid or kalingono from Lake Malawi has developed a unique hunting style; it plays dead to attract other fish to eat it, then it turns the tables by 'coming alive' and eating the would-be predator. There are 'so many other weird and wonderful species to discover', the report said, like Africa's elephant fishes, which use electrical pulses to communicate with others about sex, size, predators and prey. The cuckoo catfish gorges itself on the eggs of cichlids in Lake Tanganyika. 'Like its famous avian namesake, this fish tries to palm off parental care on an unsuspecting species. The cuckoo catfish does this by creating chaos at spawning time and confusing unsuspecting female cichlids into scooping up its spawn, which the cichlids subsequently brood in their mouths.' The African tigerfish can leap from the water to catch barn swallows in flight while the African lungfish breathes air and can survive years buried in mud during droughts. The ancient bichirs are often referred to as 'living fossils' for their lineage that predates the dinosaurs. Under-reported, undervalued and under pressure But despite their dazzling diversity and critical importance, the continent's freshwater fishes have remained 'largely invisible' to decision-makers with the benefits they contribute 'hidden and ignored' — and are now facing increasing threats to their survival. Globally, freshwater species populations are in freefall – crashing 85% since 1970. Nearly a quarter of the world's freshwater fish species are threatened with extinction. Africa's freshwater fishes are no exception. The report noted that of the 3 281 freshwater fish species, 712 are classified as threatened — with 170 listed as critically endangered, 243 listed as endangered and 299 listed as vulnerable. But the true number is higher because 536 of the continent's assessed freshwater fish are classified as data deficient, 'which means they are so poorly known that their threat status can't be assessed'. The IUCN Red List of Threatened Species classifies nine freshwater fishes as extinct — three from Morocco, two from Madagascar and one each from Kenya and Tanzania, Rwanda, Tunisia and Lake Malawi. 'However, the true number is likely to be significantly greater. For example, many species have almost certainly been lost in Lake Victoria alone.' The report said: 'When we tip the scales by drastically reducing freshwater fish populations, we undermine the functioning of freshwater ecosystems — our very life support systems. The decline in freshwater fish populations is the clearest indicator of the damage we have done — and are still doing — to Africa's rivers, lakes and wetlands. 'And that collapse of aquatic ecosystems across Africa only exacerbates the continent's freshwater fish crisis. Freshwater fishes need healthy freshwater ecosystems. And so do we. But we're losing them both far too fast.' Spawning protection The report said that very rarely are the full economic and social values of freshwater fishes and fisheries factored into decisions about hydropower dams, the draining of wetlands and dredging for navigation or sand mining, for example. 'However, there are indications that some decision-makers are finally starting to take the fate of freshwater ecosystems and fishes into account – and that the momentum for action is building.' African countries signed up to the The report said this ambitious agreement paves the way for a new approach to safeguard freshwater biodiversity, highlighted in the country-led Championed by the Democratic Republic of the Congo, Gabon and Zambia, 20 countries on the continent have already joined the challenge — the largest freshwater protection and restoration initiative in history. Meanwhile, 51 countries are members of the Ramsar Convention on Wetlands. WWF is urging African countries to adopt the The plan outlines six urgent actions including letting rivers flow more naturally; improving water quality in freshwater ecosystems; protecting and restoring critical habitats and species; ending unsustainable resource use; preventing and controlling invasive non-native species; safeguarding free-flowing rivers and removing obsolete barriers.
Mail & Guardian
02-07-2025
- General
- Mail & Guardian
Our rivers are dying — and so are the fish we've never heard of
More than 50 000 litres of sewage spews into South Africa's rivers every second, the result of a failure to maintain infrastructure and outdated wastewater treatment plants that are unable to handle current volumes. (Delwyn Verasamy/M&G) In May, Jason van den Berg and his team at The surprising presence of this species, which had not been recorded in the 'These eels have one of the most fascinating lifecycles of any local species, as they live most of their lives in freshwater rivers and dams but migrate all the way to the Indian Ocean to spawn,' Van den Berg said. 'The juveniles then return inland, sometimes travelling hundreds of kilometres upstream.' For him, such sightings not only confirm the continued existence of a rare species, but underscore the importance of ecological connectivity between inland waters and the sea. When most South Africans think of freshwater fish, exotic species such as carp and bass come to mind. However, the country's indigenous freshwater life is unique, ecologically important and yet often disregarded. 'From the small and often overlooked straightfin barb to the well-known sharptooth catfish, our inland waters hold an incredible, and often very underappreciated, diversity of native aquatic life,' he said. Many of the country's native fish species are threatened by habitat loss and pollution while the 'A very big problem for our local fish species is all these exotic fish. People basically feed dams with carp and bass for angling and a fish like bass is a predatory fish,' said Van den Berg. 'They eat all these smaller indigenous fish and their eggs and their fry and it seems that one of the biggest problems that our local fish species face is the exotic invasive species.' Dam construction, canalisation and poor waste management, can destroy critical habitats and wipe out local populations. Another major menace is the use of illegal gillnets in waterways. They cause 'indiscriminate and widespread destruction', Van den Berg said, with unsustainable harvesting hurting fish populations and also trapping terrapins, otters, birds and even crocodiles. According to the The institute's South Africa has 118 freshwater fish species, of which half are endemic, the report said. One-third of the country's native freshwater fish species are threatened. Two-thirds of the endemic taxa are threatened and most of these are concentrated in the mountainous Cape fold eco-region. The report said several localised extinctions of populations of freshwater fishes, particularly those in the genera Pseudobarbus , Sedercypris (redfins), Cheilobarbus , Sandelia and Galaxias have been recorded. Predation by 'These Van den Berg noted that one of the biggest hurdles that indigenous freshwater fish species face is that so few people even know they exist or where they still cling to life. 'Their obscurity is part of the problem,' he said. 'Without proper data and public awareness, these species risk slipping away silently — some perhaps lost before we even understand their role in the ecosystem. Rooikat Conservation is calling on the public to help it fill critical knowledge gaps by reporting all types of aquatic life — from lesser-seen indigenous fish to invasive species like redclaw crayfish as well as crabs, Cape clawless otters and even hippos and crocodiles — to the organisation. Van den Berg related how a few years ago, he bought a second-hand book on local indigenous fish. 'I was quite stunned, even with the knowledge and experience I had with the bush, to see how many species of fish there were. I think most people just aren't aware of this and there isn't really any awareness, which is why we tried creating a bit of awareness,' he said. Documenting species is the first step in protecting them, he added. 'If we don't know what's out there, or where it still survives, we can't make informed conservation decisions. Each record helps build a clearer picture of which species are thriving, which are declining, and where urgent action may be needed.' With Van den Berg cited examples of valuable reports including an indigenous straightfin barb recorded in a slow-flowing stream near Hammanskraal, with a clear photo and GPS location sent via WhatsApp; a freshwater crab spotted near Rayton, with a photo and GPS location sent via WhatsApp; a largemouth bass caught in a farm dam near Cullinan, uploaded to iNaturalist and an illegal gillnet discovered and removed from the Apies River, with photos and location. 'Many anglers, landowners and others who spend time near rivers and dams encounter species they may not realise are ecologically significant,' he said. 'With just a bit of awareness, a photo and a shared location, members of the public can provide valuable data, helping scientists and conservationists build a clearer picture of what exists and what needs protecting.' He noted that the poor conditions of freshwater ecosystems in South Africa ultimately affect humans. 'We depend on water for life. If our fishes struggle due to bad water quality, we'll follow suit … The more we toxify and damage our waterways, the more we will suffer as well.' * Contribute by sending your photo and location directly to Rooikat Conservation via WhatsApp at 076 982 0471.
Yahoo
01-07-2025
- Health
- Yahoo
Researchers issue warning after discovering game fish infected with parasite in California: 'These parasites are here in the US'
If you're eating freshwater fish in Southern California, you'll want to take extra precautions since fish have become infected with parasites. A study by the University of California, San Diego found that over 90% of game fish studied had been infected with a parasite. The study, published in the Journal of Infectious Diseases, found "two species of [parasitic] flatworms called trematodes," which typically cause weight loss, lethargy, or gastrointestinal problems when humans get infected. In rare cases, it can cause heart attacks or strokes. Haplorchis pumilio and Centrocestus formosanus were the "two species of parasitic trematodes," identified, per UC San Diego. These parasites are typically found in Southeast Asia, but it is likely that an aquatic invasive snail, known as the Malaysian trumpet snail or red-rimmed melania, brought them to the U.S. over 10 years ago. The researchers examined 84 different species of fish in 2023 from five fishing sites in San Diego County, including bluegill and largemouth; 93% were infected with the Haplorchis pumilio parasite, and "Centrocestus formosanus, was found at two of the five locations where it occurred in 91% of the fish," per UC San Diego. UC San Diego's Scripps Institution of Oceanography ecologist and parasitologist, and senior author of the study, Ryan Hechinger, said, "These parasites are here in the U.S., and they're infecting fish that people are eating." These parasites, which are appearing in freshwater fish, serve as an example of why invasive species can be dangerous. While not all non-native species are harmful, those that are can cause damage to the ecosystem and pose health risks, as in this case. The Asian tiger mosquito is another invasive species that can carry disease. It entered the U.S. in the mid-1980s, and some harbored the West Nile virus. The mosquito also invaded Europe in 2024, carrying the dengue fever virus. Invasive species also wreak havoc on the economy, causing damage to crops, livestock, and fish, costing the U.S. $20 billion a year for cleanup. Additionally, they are harmful to the environment because they take resources from native species, sometimes causing them to go extinct. How often do you worry about the quality of your drinking water? Never Sometimes Often Always Click your choice to see results and speak your mind. Hechinger said there is "no need to panic," because you can thoroughly cook or freeze your fish "for at least one week" to kill the parasites, if you plan to eat it raw, per Food and Drug Administration guidelines, as reported by UC San Diego. There have been no reported cases yet, but researchers want the parasite to be added to the diseases that public health officials are required to report. Hechinger said, "This kind of research is so important to identifying new public health threats, and it wouldn't have been possible without NIH funding." Invasive species such as this aquatic snail that is spreading parasites are one of the critical climate issues that are vital to understand to protect the public from these threats. Join our free newsletter for good news and useful tips, and don't miss this cool list of easy ways to help yourself while helping the planet.
Daily Mail
04-06-2025
- Health
- Daily Mail
Urgent warning over parasite-riddled fish eaten by millions that cause heart attacks
Nearly every single freshwater fish in Southern California may be riddled with parasites that could cause serious health issues in humans. Researchers from the University of California-San Diego revealed that a staggering 93 percent of the 84 freshwater game fish they examined carried two species of trematodes - parasitic worms that infect people who eat raw or undercooked fish. These freshwater species included bluegills, largemouth bass, green sunfish, bluegill-green sunfish hybrids, redear sunfish, black crappies, and the common carp. The two species of flatworms discovered (Haplorchis pumilio and Centrocestus formosanus) typically cause stomach problems, weight loss, and fatigue in people. However, the research team warned that particularly severe infections can lead to heart attacks of strokes. The researchers added that Americans don't often think about freshwater fish having parasites, but the outbreak has already been found in Texas, Florida, and Utah as well. Ryan Hechinger, an ecologist at UC San Diego's Scripps Institution of Oceanography said: 'These parasites are here in the US, and they're infecting fish that people are eating.' The fish are typically found in warm, shallow waters with vegetation nearby. However, this has also become a thriving habitat for the invasive snail Melanoides tuberculata, which carries the trematodes spreading to local fish. Freshwater game fish include multiple species that live in lakes, rivers, or reservoirs. They're popular targets for recreational fishing, often because anglers consider them fun to catch or good to eat. Fully cooking any fish caught in these locations will eliminate the parasites, according to guidelines from the US Food and Drug Administration (FDA). For those who eat raw fish, in items like sushi, they need to freeze their catch for at least a week to kill the trematodes. The parasites were mostly in the fins and gills, though H. pumilio was often found in the muscle tissue near fin bases, which could end up in fish fillets. Overall, researchers found 78 of the 84 fish they examined are carrying the parasitic worms. Other popular freshwater game fish that could be at risk from the snail's parasites include catfish, trout, salmon, and perch. The study authors fear that millions of people could be at risk of contamination, based on the amount of interest in eating raw fish on social media and platforms like YouTube. During their study, published in the Journal of Infectious Diseases, Hechinger's team also looked at 125 popular YouTube videos which featured people eating raw freshwater fish. Nearly two-thirds (65%) did not mention the proper cooking or freezing methods for these fish, which the team believes is promoting bad habits and will likely lead to the spread of dangerous parasites among seafood lovers. According to the study authors, many videos also spread false information, like claiming that marinating fish in citrus juice or choosing 'healthy-looking' fish eliminates the risk of parasites, which isn't true. While there hasn't been widespread outbreak of trematode infections reported in California or elsewhere, Hechinger said that doesn't mean many people aren't getting sick. 'Nobody is looking for cases and doctors aren't required to report them,' he explained. Hechinger added that his team believes fish-borne trematode infections should be added to the list of diseases doctors have to report to public health officials. The FDA explains that improper cooking of fish means it hasn't reached an internal temperature of at least 145°F. For those freezing their fish to eat it raw, it needs to reach a temperature of -4°F for seven days or be flash-frozen at -31°F for at least 15 hours. When fish is improperly cooked or frozen, the trematodes can survive and then infect the human body when eaten. Once swallowed, these parasites enter your stomach and not even the stomach's acids can kill the larvae, which are protected by a cyst-like covering. In the small intestine, digestive enzymes break down this covering and release the young worms into the gastrointestinal tract. Over the next few days to weeks, the juvenile worms grow into adults, which are about one to two millimeters long. As the worms multiply and attach themselves to the small intestine, they irritate the intestinal lining, leading to symptoms like stomach pain, diarrhea, nausea, and indigestion. After eating infected fish, most symptoms of H. pumilio or C. formosanus typically start within one to two weeks. If left untreated, the more severe symptoms of a chronic infection could start to show one to three months after eating the fish. Once doctors diagnose someone with an infection, the standard treatment is an anti-parasitic medication called Praziquantel. The infections typically clear up within days after taking the drug.
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The Independent
03-06-2025
- General
- The Independent
California fish carry human-infecting parasites that can cause stroke or heart attack, researchers find
More than 90 percent of popular freshwater game fish in Southern California contain a parasite that is capable of inducing strokes or heart attacks in the humans who eat them. Researchers said the parasites were two species of flatworms known as trematodes. At no more than a few centimeters in length, the flukes – a class of flatworms – can result in weight loss or lethargy. Although rare, infection has also resulted in more severe consequences. 'Americans don't usually think about parasites when they eat freshwater fish because it hasn't historically been an issue here,' Ryan Hechinger, an ecologist and parasitologist at UC San Diego's Scripps Institution of Oceanography, said in a statement. 'But these trematodes have now been widely introduced in the U.S. and that means that doctors and the public should be aware.' He is the senior author of the study which was published Tuesday in the Journal of Infectious Diseases. It was funded by the National Institutes of Health. To identify this issue, Hechinger, the University of Nebraska's Daniel Metz, and former Scripps graduate student and Smithsonian Environmental Research Center marine scientist Emma Palmer examined 84 fish from seven different species in 2023. Those fish included largemouth bass and bluegill, which were collected from five frequented fishing locations in San Diego County. Of those, 93 percent were infected with the Haplorchis pumilio parasite, and some were the host to thousands. Two of the five locations yielded positive results for the second parasite known as Centrocestus formosanus, which occurred in 91 percent of the fish. Historically, the trematodes have infected people in Southeast Asia and likely arrived in the U.S. more than a decade ago inside an invasive aquatic snail known as the red-rimmed melania. That snail is found in 17 states and Puerto Rico. Previous work led by Hechinger had found that the red-rimmed melania and its parasites are widespread in the Golden State. So, what is the risk to Californians and Americans at large? Hechinger says there haven't been any reported cases of parasites infecting Americans yets, but 'nobody is looking for cases and doctors aren't required to report them.' Californians should make sure to monitor fish advisories for any changes. The risks posed by them are easy to avoid as, if you fully cook your fish or freeze any that's intended to be eaten raw for at least a week, the parasites will die. Although, the authors found that many Americans are likely consuming freshwater fish without taking the proper precautions. The greatest health threats come from repeated infection over many months or years. Foodborne trematode infections cause two million life years lost to disability and death worldwide every year, according to the World Health Organization. They recommend that fish-borne trematode infection be added to the list of diseases doctors are required to report to public health officials. 'These parasites are here in the U.S., and they're infecting fish that people are eating,' said Hechinger. 'We hope this study can help make public health officials, doctors and the public more aware.'
