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As fish deaths increase at pumps, critics urge California agencies to improve protections

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Monday, April 8, 2024

Powerful pumps that supply much of California’s population with water have killed several thousand threatened and endangered fish this year, prompting a coalition of environmental groups to demand that state and federal agencies take immediate steps to limit “alarming levels” of deaths. In a letter to state and federal water managers, leaders of five fishing and environmental groups said the estimated losses of threatened steelhead trout and endangered winter-run Chinook salmon have exceeded maximum annual limits for water intakes in the Sacramento-San Joaquin River Delta.“Given that these and other species in the Bay-Delta are at grave risk of extinction, we want to emphasize the need for urgent action,” the environmental advocates wrote. Aggressive and impactful reporting on climate change, the environment, health and science. The massive pumps that draw water into the aqueducts of the State Water Project and the Central Valley Project are strong enough to reverse the flow in parts of the south delta. They can also suck fish into their machinery or make them easy prey for predators. Because of this, pumping facilities are assigned annual take limits for certain fish under the Endangered Species Act. The environmental groups are urging water managers to scale back pumping until juvenile salmon and steelhead have finished migrating through the delta and into San Francisco Bay. “To see the state and federal water agencies exceed their take limits and continue business-as-usual water exports is like witnessing extinction in real time,” said Jon Rosenfield, science director of San Francisco Baykeeper. “It demonstrates the official negligence and lawlessness that caused these fish, and many others, to become endangered in the first place.”State water officials say they have been taking substantial measures to protect fish. They say the large numbers of fish that have moved into areas around the water intakes have caused them to pump less than they typically would based on current conditions.The losses are calculated based on the numbers of fish that are collected — scooped from the water in a bucket-like device at the state facility — then transported by truck and released into the delta nearby. The calculations attempt to account for fish that are caught by predators and those that are killed when they are drawn into pumps. The Harvey O. Banks Delta Pumping Plant in Alameda County lifts water into the California Aqueduct. (California Department of Water Resources) According to the California Department of Fish and Wildlife, estimated losses of steelhead trout exceeded the annual incidental take limit of 2,760 on March 20. By the end of March, the department said, the estimated losses of naturally spawned steelhead since Dec. 1 had risen to 3,374.The estimated losses of endangered winter-run Chinook salmon also exceeded the annual loss threshold of 2,748 on March 20. Those estimated losses have since risen to 4,049, according to the Department of Fish and Wildlife.State wildlife officials said the estimates are for fish that spawned naturally in rivers and don’t include losses of hatchery-raised fish.(There is a caveat to the estimated losses of winter-run Chinook. State officials say they base their calculations on fish that are the size of winter-run Chinook rather than those that are genetically confirmed to be this type of salmon. As a result, officials say, some of the estimated losses are actually different types of salmon.)The Department of Water Resources “is closely monitoring the collection system at the fish screens in front of the State Water Project pumps in the south delta,” said Karla Nemeth, the agency’s director.“The majority of Chinook salmon and steelhead collected at the fish screens are collected alive and transported downstream of the pumps. We have been adjusting pumping operations to protect listed and endangered species,” Nemeth said in an email. “However, [State Water Project] operations have never been this restricted in a wet year as they are this year. These restrictions are keeping us from being able to capture and store the water that we need if we see a return to drought conditions.”The pumps that supply the State Water Project have been operating far below their capacity over the past three months. Agencies that receive supplies have been told to plan for 30% of their full allocations this year.The permits and biological opinions that govern state and federal pumping operations include measures aimed at limiting the deaths of fish. In response to the losses, state and federal officials have been discussing measures being taken to protect fish.Rosenfield said the water agencies aren’t doing nearly enough and argued that the losses put them in violation of permits.“If you and I were out there killing hundreds and thousands of endangered fish, we’d be in jail,” Rosenfield said. “They’re not doing everything they can do to prevent the harm and mitigate the damage. There’s an opportunity to protect these fish by reducing water exports. It’s urgent ... and they’re doing nothing.”The environmental and fishing groups — which include Defenders of Wildlife, the Bay Institute, Golden State Salmon Assn. and the California Sportfishing Protection Alliance — pointed to notes from a March 6 meeting at which officials from the National Marine Fisheries Service proposed reducing pumping to very low levels “as soon as possible, for a minimum of five days, and then reassessing.”The groups said that despite this advice from fishery officials, the Department of Water Resources and federal Bureau of Reclamation “ignored these recommendations and continued to export water at rates that killed thousands of imperiled fishes.”Lenny Grimaldo, environmental director for the State Water Project, said in an interview with The Times that officials have kept pumping to levels they deemed were “protective of minimizing additional losses of fish but also protective of water supply.”In an email, Grimaldo said that before the take limit for steelhead was reached on March 20, pumping at the State Water Project was reduced to protect the fish, and pumping remained at those low levels — around 1,200 cubic feet per second — through March 26 “to minimize further loss.”Then, based on new information indicating that a higher level of pumping would “not draw any additional steelhead into the zone of the pumps,” Grimaldo said, the state consulted with federal officials and decided to “slightly increase exports” to 2,200 cubic feet per second on March 26.The state and federal facilities were drawing in 2,400 cubic feet per second through Thursday, operating at a little over 20% of their combined capacity, Grimaldo said. After runoff from the latest storms boosted river flows, state officials on Friday said they were increasing water exports to 3,900 cubic feet per second, or 35% of full capacity, over the following five days. Grimaldo said the Department of Water Resources “is continuing to comply with endangered species regulations, including ongoing consultation” with other state and federal agencies. The state agency is also investing in “rapid genetic technology” to better distinguish endangered winter-run salmon from other types, Grimaldo said, and to comply with requirements under law. In the southern Sacramento-San Joaquin River Delta, water passes through an inlet structure at Clifton Court Forebay, near the pumping plant that draws water into the State Water Project. (California Department of Water Resources) State officials said the agencies have formed a scientific review panel to study ways of improving operations.“I’m concerned about this situation because I feel like these species are getting the short end of the stick,” said Ashley Overhouse, water policy adviser for Defenders of Wildlife.She said that after one of the wettest winters on record, in 2023, and an above-average winter this year, it’s an optimal time for helping fish populations begin to recover from years of drought. Other species that are at risk include threatened green sturgeon and endangered delta smelt. The population of threatened spring-run Chinook salmon has also suffered declines, and last year the fishing season for fall-run Chinook was canceled because of low population estimates.“We have an estuary that’s the heart of our water management system and on the brink of collapse,” Overhouse said. “We are at a critical turning point, and any additional attention, coordination and, frankly, collective efforts and action that we can take to make sure that this doesn’t happen again is paramount.”She said she hopes the outcry will spur discussion to protect fish populations.“I think it’s possible. It’s just unfortunate that so many fish have to die in the process to get there,” Overhouse said.The losses of fish coincide with other debates over how water should be managed in the delta. Regulators are considering alternatives for new standards and flow requirements that will determine how much water may be drawn from the delta.Additionally, Gov. Gavin Newsom presented a plan last week outlining his administration’s priorities for changing how the state manages water to adapt to more extreme droughts and floods related to climate change. Newsom’s priorities include fast-tracking development of Sites Reservoir, the first new major reservoir in decades, and moving ahead with the proposed Delta Conveyance Project, a 45-mile tunnel that would transport water beneath the delta.Nemeth said the restrictions on pumping have come at a cost to supplies. With a likely return of La Niña that could bring drier conditions, she said, “now is the time to capture and store this water while it’s available.”“These conditions speak to the critical need to continue to advance the Delta Conveyance Project, which is an important part of how we can manage the impacts of climate change,” Nemeth said.She said that in a wet year like this, the tunnel would allow the state to capture more water during high flows and store it for dry times, and “do so in a way that minimizes impacts to fish species.”Rosenfield disagrees. He said state officials are wrongly assuming that tunnel fish screens would be more effective and argued that the tunnel would harm endangered fish and the delta’s ecosystem.The rise in fish deaths is a symptom of a larger problem, Rosenfield said: California diverts too much water from the delta, to the detriment of its ecological health.“From the fishes’ perspective, our unsustainable water diversions cause a nearly continuous, man-made drought — a drought so severe that numerous species that have thrived in the delta for eons are all declining toward extinction,” he said. “A delta tunnel will divert more water, not less.”

Environmental groups are urging water managers to scale back pumping until juvenile salmon and steelhead have finished migrating through the delta and into San Francisco Bay.

Powerful pumps that supply much of California’s population with water have killed several thousand threatened and endangered fish this year, prompting a coalition of environmental groups to demand that state and federal agencies take immediate steps to limit “alarming levels” of deaths.

In a letter to state and federal water managers, leaders of five fishing and environmental groups said the estimated losses of threatened steelhead trout and endangered winter-run Chinook salmon have exceeded maximum annual limits for water intakes in the Sacramento-San Joaquin River Delta.

“Given that these and other species in the Bay-Delta are at grave risk of extinction, we want to emphasize the need for urgent action,” the environmental advocates wrote.

Aggressive and impactful reporting on climate change, the environment, health and science.

The massive pumps that draw water into the aqueducts of the State Water Project and the Central Valley Project are strong enough to reverse the flow in parts of the south delta. They can also suck fish into their machinery or make them easy prey for predators. Because of this, pumping facilities are assigned annual take limits for certain fish under the Endangered Species Act.

The environmental groups are urging water managers to scale back pumping until juvenile salmon and steelhead have finished migrating through the delta and into San Francisco Bay.

“To see the state and federal water agencies exceed their take limits and continue business-as-usual water exports is like witnessing extinction in real time,” said Jon Rosenfield, science director of San Francisco Baykeeper. “It demonstrates the official negligence and lawlessness that caused these fish, and many others, to become endangered in the first place.”

State water officials say they have been taking substantial measures to protect fish. They say the large numbers of fish that have moved into areas around the water intakes have caused them to pump less than they typically would based on current conditions.

The losses are calculated based on the numbers of fish that are collected — scooped from the water in a bucket-like device at the state facility — then transported by truck and released into the delta nearby. The calculations attempt to account for fish that are caught by predators and those that are killed when they are drawn into pumps.

An aerial view of the Harvey O. Banks Delta Pumping Plant.

The Harvey O. Banks Delta Pumping Plant in Alameda County lifts water into the California Aqueduct.

(California Department of Water Resources)

According to the California Department of Fish and Wildlife, estimated losses of steelhead trout exceeded the annual incidental take limit of 2,760 on March 20. By the end of March, the department said, the estimated losses of naturally spawned steelhead since Dec. 1 had risen to 3,374.

The estimated losses of endangered winter-run Chinook salmon also exceeded the annual loss threshold of 2,748 on March 20. Those estimated losses have since risen to 4,049, according to the Department of Fish and Wildlife.

State wildlife officials said the estimates are for fish that spawned naturally in rivers and don’t include losses of hatchery-raised fish.

(There is a caveat to the estimated losses of winter-run Chinook. State officials say they base their calculations on fish that are the size of winter-run Chinook rather than those that are genetically confirmed to be this type of salmon. As a result, officials say, some of the estimated losses are actually different types of salmon.)

The Department of Water Resources “is closely monitoring the collection system at the fish screens in front of the State Water Project pumps in the south delta,” said Karla Nemeth, the agency’s director.

“The majority of Chinook salmon and steelhead collected at the fish screens are collected alive and transported downstream of the pumps. We have been adjusting pumping operations to protect listed and endangered species,” Nemeth said in an email. “However, [State Water Project] operations have never been this restricted in a wet year as they are this year. These restrictions are keeping us from being able to capture and store the water that we need if we see a return to drought conditions.”

The pumps that supply the State Water Project have been operating far below their capacity over the past three months. Agencies that receive supplies have been told to plan for 30% of their full allocations this year.

The permits and biological opinions that govern state and federal pumping operations include measures aimed at limiting the deaths of fish. In response to the losses, state and federal officials have been discussing measures being taken to protect fish.

Rosenfield said the water agencies aren’t doing nearly enough and argued that the losses put them in violation of permits.

“If you and I were out there killing hundreds and thousands of endangered fish, we’d be in jail,” Rosenfield said. “They’re not doing everything they can do to prevent the harm and mitigate the damage. There’s an opportunity to protect these fish by reducing water exports. It’s urgent ... and they’re doing nothing.”

The environmental and fishing groups — which include Defenders of Wildlife, the Bay Institute, Golden State Salmon Assn. and the California Sportfishing Protection Alliance — pointed to notes from a March 6 meeting at which officials from the National Marine Fisheries Service proposed reducing pumping to very low levels “as soon as possible, for a minimum of five days, and then reassessing.”

The groups said that despite this advice from fishery officials, the Department of Water Resources and federal Bureau of Reclamation “ignored these recommendations and continued to export water at rates that killed thousands of imperiled fishes.”

Lenny Grimaldo, environmental director for the State Water Project, said in an interview with The Times that officials have kept pumping to levels they deemed were “protective of minimizing additional losses of fish but also protective of water supply.”

In an email, Grimaldo said that before the take limit for steelhead was reached on March 20, pumping at the State Water Project was reduced to protect the fish, and pumping remained at those low levels — around 1,200 cubic feet per second — through March 26 “to minimize further loss.”

Then, based on new information indicating that a higher level of pumping would “not draw any additional steelhead into the zone of the pumps,” Grimaldo said, the state consulted with federal officials and decided to “slightly increase exports” to 2,200 cubic feet per second on March 26.

The state and federal facilities were drawing in 2,400 cubic feet per second through Thursday, operating at a little over 20% of their combined capacity, Grimaldo said. After runoff from the latest storms boosted river flows, state officials on Friday said they were increasing water exports to 3,900 cubic feet per second, or 35% of full capacity, over the following five days.

Grimaldo said the Department of Water Resources “is continuing to comply with endangered species regulations, including ongoing consultation” with other state and federal agencies. The state agency is also investing in “rapid genetic technology” to better distinguish endangered winter-run salmon from other types, Grimaldo said, and to comply with requirements under law.

Water passes through an inlet structure in the Sacramento-San Joaquin River Delta.

In the southern Sacramento-San Joaquin River Delta, water passes through an inlet structure at Clifton Court Forebay, near the pumping plant that draws water into the State Water Project.

(California Department of Water Resources)

State officials said the agencies have formed a scientific review panel to study ways of improving operations.

“I’m concerned about this situation because I feel like these species are getting the short end of the stick,” said Ashley Overhouse, water policy adviser for Defenders of Wildlife.

She said that after one of the wettest winters on record, in 2023, and an above-average winter this year, it’s an optimal time for helping fish populations begin to recover from years of drought.

Other species that are at risk include threatened green sturgeon and endangered delta smelt. The population of threatened spring-run Chinook salmon has also suffered declines, and last year the fishing season for fall-run Chinook was canceled because of low population estimates.

“We have an estuary that’s the heart of our water management system and on the brink of collapse,” Overhouse said. “We are at a critical turning point, and any additional attention, coordination and, frankly, collective efforts and action that we can take to make sure that this doesn’t happen again is paramount.”

She said she hopes the outcry will spur discussion to protect fish populations.

“I think it’s possible. It’s just unfortunate that so many fish have to die in the process to get there,” Overhouse said.

The losses of fish coincide with other debates over how water should be managed in the delta. Regulators are considering alternatives for new standards and flow requirements that will determine how much water may be drawn from the delta.

Additionally, Gov. Gavin Newsom presented a plan last week outlining his administration’s priorities for changing how the state manages water to adapt to more extreme droughts and floods related to climate change. Newsom’s priorities include fast-tracking development of Sites Reservoir, the first new major reservoir in decades, and moving ahead with the proposed Delta Conveyance Project, a 45-mile tunnel that would transport water beneath the delta.

Nemeth said the restrictions on pumping have come at a cost to supplies. With a likely return of La Niña that could bring drier conditions, she said, “now is the time to capture and store this water while it’s available.”

“These conditions speak to the critical need to continue to advance the Delta Conveyance Project, which is an important part of how we can manage the impacts of climate change,” Nemeth said.

She said that in a wet year like this, the tunnel would allow the state to capture more water during high flows and store it for dry times, and “do so in a way that minimizes impacts to fish species.”

Rosenfield disagrees. He said state officials are wrongly assuming that tunnel fish screens would be more effective and argued that the tunnel would harm endangered fish and the delta’s ecosystem.

The rise in fish deaths is a symptom of a larger problem, Rosenfield said: California diverts too much water from the delta, to the detriment of its ecological health.

“From the fishes’ perspective, our unsustainable water diversions cause a nearly continuous, man-made drought — a drought so severe that numerous species that have thrived in the delta for eons are all declining toward extinction,” he said. “A delta tunnel will divert more water, not less.”

Read the full story here.
Photos courtesy of

Is there such a thing as a ‘problem shark’? Plan to catch repeat biters divides scientists

Some experts think a few sharks may be responsible for a disproportionate number of attacks. Should they be hunted down?First was the French tourist, killed while swimming off Saint-Martin in December 2020. The manager of a nearby water sports club raced out in a dinghy to help, only to find her lifeless body floating face down, a gaping wound where part of her right thigh should have been. Then, a month later, another victim. Several Caribbean islands away, a woman snorkelling off St Kitts and Nevis was badly bitten on her left leg by a shark. Fortunately, she survived.Soon after the fatal incident in December, Eric Clua, a marine biologist at the École Pratique des Hautes Études in Paris, got a phone call. Island nations often ask for his help after a shark bite, he says, “because I am actually presenting a new vision … I say, ‘You don’t have a problem with sharks, you have a problem with one shark.’” Continue reading...

First was the French tourist, killed while swimming off Saint-Martin in December 2020. The manager of a nearby water sports club raced out in a dinghy to help, only to find her lifeless body floating face down, a gaping wound where part of her right thigh should have been. Then, a month later, another victim. Several Caribbean islands away, a woman snorkelling off St Kitts and Nevis was badly bitten on her left leg by a shark. Fortunately, she survived.Soon after the fatal incident in December, Eric Clua, a marine biologist at the École Pratique des Hautes Études in Paris, got a phone call. Island nations often ask for his help after a shark bite, he says, “because I am actually presenting a new vision … I say, ‘You don’t have a problem with sharks, you have a problem with one shark.’”Human-shark conflicts are not solely the result of accidents or happenstance, Clua says. Instead, he says there are such things as problem sharks: bold individuals that may have learned, perhaps while still young, that humans are prey. It’s a controversial stance, but Clua thinks that if it’s true – and if he can identify and remove these problem sharks – it might dissuade authorities from taking even more extreme forms of retribution, including culls.A shark killed a man at Long Reef beach in Dee Why, Sydney, on 6 September, 2025. Photograph: Dean Lewins/AAPThough culls of sharks after human-shark conflict are becoming less common and are generally regarded by scientists as ineffective, they do still happen. One of the last big culls took place near Réunion, a French island in the Indian Ocean, between 2011 and 2013, resulting in the deaths of more than 500 sharks. Even that was not enough for some – four years later, a professional surfer called for daily shark culls near the island.And so, in the immediate aftermath of the French tourist’s death in Saint-Martin, when one of Clua’s contacts called to explain what had happened, he recalls telling them: “Just go there on the beach … I want swabbing of the wounds.”After that bite and the one that occurred a month later, medical professionals collected samples of mucus that the shark had left behind to send off for analysis, though it took weeks for the results to come back. But as Clua and colleagues describe in a study published last year, the DNA analysis confirmed that the same tiger shark was responsible for both incidents.Even before the DNA test was complete, however, analysis of the teeth marks left on the Saint-Martin victim, and of the tooth fragment collected from her leg, suggested the perpetrator was a tiger shark (Galeocerdo cuvier) roughly 3 metres (10ft) long. Armed with this knowledge, Clua and his colleagues set out to catch the killer.During January and February 2021, Clua and his team hauled 24 tiger sharks from the water off Saint-Martin and analysed a further 25 sharks that they caught either around St Barts or St Kitts and Nevis.Eric Clua and his colleagues took DNA samples from nearly 50 tiger sharks to try to find one that had bitten two women. Photograph: Courtesy of Eric CluaBecause both of the women who were bitten had lost a substantial amount of flesh, the scientists saw this as a chance to find the shark responsible. Each time they dragged a tiger shark out of the water they flipped it upside down, flooded its innards with water, and pressed firmly on its stomach to make it vomit. A shark is, generally, “a very easy puker”, Clua says. The team’s examinations turned up no evidence of human remains.Clua and his colleagues also took DNA samples from each of the tiger sharks, as well as from dead sharks landed by fishers in St Kitts and Nevis. None matched the DNA swabbed from the wounds suffered by the two women.But the team has not given up. Clua is now waiting for DNA analysis of mucus samples recovered from a third shark bite that happened off Saint-Martin in May 2024. If that matches samples from the earlier bites, Clua says, that would suggest it “might be possible” to catch the culprit shark in the future.For people who don’t want to risk interacting with sharks, I have great news – swimming pools existCatherine Macdonald, conservation biologistThat some specific sharks have developed a propensity for biting people is controversial among marine scientists, though Lucille Chapuis, a marine sensory ecologist at La Trobe University in Australia, is not entirely sure why. The concept of problem animals is well established on land, she says. Terrestrial land managers routinely contend with problem lions, tigers and bears. “Why not a fish?” asks Chapuis. “We know that fishes, including sharks, have amazing cognitive abilities.”Yet having gleaned a range of opinions on Clua’s ideas, some marine scientists rejected the concept of problem sharks outright.A tiger shark. Some scientists fear that merely talking about problem sharks could perpetuate the preconception of human-eating monsters. Photograph: Jeff Milisen/AlamyClua is aware that his approach is divisive: “I have many colleagues – experts – that are against the work I’m doing.”The biggest pushback is from scientists who say there is no concrete evidence for the idea that there are extra dangerous, human-biting sharks roaming the seas. Merely talking about problem sharks, they say, could perpetuate the idea that some sharks are hungry, human-eating monsters such as the beast from the wildly unscientific movie Jaws.Clua says the monster from Jaws and his definition of a problem shark are completely different. A problem shark is not savage or extreme; it’s just a shark that learned at some point that humans are among the things it might prey on. Environmental factors, as well as personality, might trigger or aggravate such behaviour.Besides the tiger shark that struck off Saint-Martin and St Kitts and Nevis, Clua’s 2024 study detailed the case of another tiger shark involved in multiple bites in Costa Rica. A third case focused on an oceanic whitetip shark in Egypt that killed a female swimmer by biting off her right leg. The same shark later attempted to bite the shoulder of one of Clua’s colleagues during a dive.Pilot fish follow an oceanic whitetip shark. A woman was killed when an oceanic whitetip bit off her right leg in Egypt. Photograph: Amar and Isabelle Guillen/Guillen Photo LLC/AlamyToby Daly-Engel, a shark expert at the Florida Institute of Technology, says the genetic analysis connecting the same tiger shark to two bite victims in the Caribbean is robust. However, she says such behaviour must be rare. “They’re just opportunistic. I mean, these things eat tyres.”Diego Biston Vaz, curator of fishes at the Natural History Museum in London, also praises Clua’s work, calling it “really forensic”. He, too, emphasises it should not be taken as an excuse to demonise sharks. “They’re not villains; they’re just trying to survive,” he says.Chapuis adds that the small number of animals involved in Clua’s recent studies mean the research does not prove problem sharks are real. Plus, while some sharks might learn to bite humans, she questions whether they would continue to do so long term. People tend to defend themselves well and, given there are only a few dozen unprovoked shark bites recorded around the world each year, she says there is no data to support the idea that even the boldest sharks benefit from biting people.Plus, Clua’s plan – to capture problem sharks and bring them to justice – is unrealistic, says David Shiffman, a marine conservation biologist based in Washington DC. Even if scientists can prove beyond doubt that a few specific sharks are responsible for a string of incidents – “which I do not believe he has done”, Shiffman adds – he thinks finding those sharks is not viable.Any resources used to track down problem sharks would be better spent on preventive measures such as lifeguards, who could spot sharks approaching a busy beach, says Catherine Macdonald, a conservation biologist at the University of Miami in Florida.While identifying and removing a problem shark is better than culling large numbers, she urges people to answer harder questions about coexisting with predators. “For people who don’t want to risk interacting with sharks, I have great news,” she says. “Swimming pools exist.”Identifying and removing a problem shark is often regarded as better than culling large numbers. Photograph: Humane Society International/AAPClua, for his part, intends to carry on. He’s working with colleagues on Saint-Martin to swab shark-bite injuries when they occur, and to track down potential problem sharks.Asked whether he has ever experienced a dangerous encounter with a large shark himself, Clua says that in 58 years of diving it has happened only once, while spear fishing off New Caledonia. Poised underwater, waiting for a fish to appear, he turned his head. “There was a bull shark coming [toward] my back,” he says.He got the feeling at that moment that he was about to become prey. But there was no violence. Clua looked at the bull shark as it turned and swam away.This story was originally published in bioGraphic, an independent magazine about nature and regeneration from the California Academy of Sciences.

Engineers Create Soft Robots That Can Literally Walk on Water

Scientists have developed HydroSpread, a novel technique for building soft robots on water, with wide-ranging possibilities in robotics, healthcare, and environmental monitoring. Picture a miniature robot, no larger than a leaf, gliding effortlessly across the surface of a pond, much like a water strider. In the future, machines of this scale could be deployed to [...]

The walking mechanism of the “water spider” robot HydroBuckler prototype shown here is driven by “leg” buckling. Credit: Baoxing Xu, UVA School of Engineering and Applied ScienceScientists have developed HydroSpread, a novel technique for building soft robots on water, with wide-ranging possibilities in robotics, healthcare, and environmental monitoring. Picture a miniature robot, no larger than a leaf, gliding effortlessly across the surface of a pond, much like a water strider. In the future, machines of this scale could be deployed to monitor pollution, gather water samples, or explore flooded zones too hazardous for people. At the University of Virginia’s School of Engineering and Applied Science, mechanical and aerospace engineering professor Baoxing Xu is working on a way to make such devices a reality. His team’s latest study, published in Science Advances, unveils HydroSpread, a fabrication method unlike any before it. The approach enables researchers to create soft, buoyant machines directly on water, a breakthrough with applications that could range from medical care to consumer electronics to environmental monitoring. Previously, producing the thin and flexible films essential for soft robotics required building them on solid surfaces such as glass. The fragile layers then had to be lifted off and placed onto water, a tricky procedure that frequently led to tearing and material loss. HydroSpread sidesteps this issue by letting liquid itself serve as the “workbench.” Droplets of liquid polymer could naturally spread into ultrathin, uniform sheets on the water’s surface. With a finely tuned laser, Xu’s team can then carve these sheets into complex patterns — circles, strips, even the UVA logo — with remarkable precision. From Films to Moving Machines Using this approach, the researchers built two insect-like prototypes: HydroFlexor, which paddles across the surface using fin-like motions. HydroBuckler, which “walks” forward with buckling legs, inspired by water striders. In the lab, the team powered these devices with an overhead infrared heater. As the films warmed, their layered structure bent or buckled, creating paddling or walking motions. By cycling the heat on and off, the devices could adjust their speed and even turn — proof that controlled, repeatable movement is possible. Future versions could be designed to respond to sunlight, magnetic fields, or tiny embedded heaters, opening the door to autonomous soft robots that can move and adapt on their own. “Fabricating the film directly on liquid gives us an unprecedented level of integration and precision,” Xu said. “Instead of building on a rigid surface and then transferring the device, we let the liquid do the work to provide a perfectly smooth platform, reducing failure at every step.” The potential reaches beyond soft robots. By making it easier to form delicate films without damaging them, HydroSpread could open new possibilities for creating wearable medical sensors, flexible electronics, and environmental monitors — tools that need to be thin, soft and durable in settings where traditional rigid materials don’t work. Reference: “Processing soft thin films on liquid surface for seamless creation of on-liquid walkable devices” by Ziyu Chen, Mengtian Yin and Baoxing Xu, 24 September 2025, Science Advances.DOI: 10.1126/sciadv.ady9840 Never miss a breakthrough: Join the SciTechDaily newsletter.

Whales are getting tangled in lines and ropes off the California coast in record numbers

A NOAA report shows that more whales were killed in US waters this year by entanglements than any prior year.

The number of whales getting tangled up in fishing nets, line, buoys and other miscellaneous rope off the coasts of the United States hit a record high in 2024, with California taking the ignominious lead.According to the National Oceanographic and Atmospheric Administration, there were 95 confirmed entangled whales in U.S. waters last year. Eighty-seven were live animals, while reports for eight came in after the animals had died.On average, 71 whales are reported entangled each year. There were 64 in 2023.More than 70% of the reports were from the coastal waters off California, Alaska, Hawaii and Massachusetts. California accounted for 25% in 2024, most in the San Francisco and Monterey bay areas.Humpback whales were hardest hit, accounting for 77 of the cases. Other whale species include North Pacific gray whales, the North Atlantic right whale, minke, sperm, fin and bowhead whales.Entanglements are just one of many threats facing whales worldwide. Earlier this year, 21 gray whales died in Bay Area waters, mostly after getting struck by ships. The animals are increasingly stressed from changes in food availability, shipping traffic, noise pollution, waste discharge, disease and plastic debris, and their ability to avoid and survive these impediments is diminishing. Since 2007, more than 920 humpback whales have been maimed or killed by long line ropes that commercial crabbers use to haul up cages from the sea floor. The report notes that about half the incidents are directly tied to commercial and recreational fishing lines. The remaining 49 also involved line and buoys but in circumstances that could not be traced back to a specific fishery. The report comes after years of government and conservation group efforts with the commercial fishing industry to increase awareness and encourage different fishing technologies — such as pop-up fishing gear, which uses a remote controlled pop-up balloon device to bring cages to the surface, rather than relying on lines.It also comes as funding for NOAA is threatened and Congress is considering draft legislation that would weaken the Marine Mammal Protection Act, one of the country’s foundational environmental laws, signed by President Nixon in 1972.“This report paints a clear picture: our current safeguards are not enough,” said Gib Brogan, campaign director for Oceana, an ocean advocacy group, in a statement. He said things are likely to get worse if NOAA’s funding is cut and the Marine Mammal Protection Act is eroded. “These findings underscore an urgent need for coordinated action,” said Kathi George, the Sausalito-based Marine Mammal Center’s director of cetacean conservation in a statement. “Together, we can apply the best available science to reduce the risk of entanglement, through strategies like supporting fisher-led initiatives, improving detection and response efforts, and enhancing reporting and data sharing.”

Portland State researchers hope project will reduce mega earthquake damage

The researchers are working on a soil treatment that focuses on activating microbes to reduce groundwater saturation levels – they believe it could become a cost-effective, long-lasting solution to reduce earthquake-caused liquefaction.

If and when a Cascadia Subduction Zone earthquake hits the Portland region, soil liquefaction could dramatically worsen the damage, leading buildings to tilt, roads to buckle and utility lines to rupture. Especially susceptible are sandy and silty soils – like those by the Willamette River where aging tanks store fuels including gasoline, diesel and biofuel. Intense shaking during an earthquake could cause those soils to behave more like a liquid than a solid, leading the tanks to crack, collapse, spill and explode. But Portland State University researchers say soil microbes could help prevent the destruction. The researchers are working on a soil treatment that focuses on activating microbes to reduce groundwater saturation levels – and they believe it could become a cost-effective, long-lasting solution to reduce earthquake risk in their own city and across the region. “We recognized that it would be an opportunity to test it in Portland to see if it could be applied in areas like the CEI Hub,” said Diane Moug, one of the lead researchers of the PSU microbial treatment study and an assistant professor of civil and environmental engineering at the school.The treatment is one of several new soil-based solutions being developed to prevent or reduce liquefaction – but, unlike traditional soil improvement methods, the microbe technique is based in nature and doesn’t entail invasive procedures such as injecting cement into the ground or repeatedly dropping large weights to compact the soil, said Ellen Rathje, a professor of geotechnical engineering at the University of Texas at Austin. “This area of research is a very hot topic right now,” said Rathje, who is also president of the Earthquake Engineering Research Institute, a nonprofit for experts working to reduce earthquake risks. “There’s promise in the bio-inspired techniques because there are very limited approaches you can use for sites that have already been developed. And they’re inspired by naturally occurring processes, so they’re certainly good from a sustainability perspective.”Dubbed microbially induced desaturation, the method being tested by PSU entails injecting the layers of soil that lie beneath the surface with a mixture containing calcium acetate and calcium nitrate. And then waiting. The mixture acts as a food source for naturally occurring soil microbes, stimulating their growth, said Arash Khosravifar, the co-leader of the PSU project and an associate professor of civil and environmental engineering at the school.The microbes produce large amounts of nitrogen gas and carbon dioxide – a chemical reaction called denitrification. Those nitrogen gas bubbles, in turn, fill the tiny spaces between soil particles, reducing the soil’s saturation and making it more resistant to liquefaction, Khosravifar said. In the event of an earthquake, the trapped gas bubbles act like shock absorbers, dampening water pressure buildup in the soil during intense shaking, he said. Scientists believe Oregon is overdue for the Big One, a mega earthquake that will occur just off the Oregon coast along the Cascadia Subduction Zone where the Juan de Fuca Plate pushes beneath the North American Plate – and its shaking will devastate Portland. The last major Cascadia Subduction Zone quake happened in 1700 and there’s about a 37% chance that one of 7.1 magnitude or larger will occur in the next 50 years, according to the Oregon Department of Emergency Management. The state and city of Portland have mapped liquefaction risks, finding they’re among the highest along the Columbia and Willamette rivers, including the Critical Energy Infrastructure Hub where hundreds of fuel-filled tanks sit atop a six-mile stretch of unstable soils. Three years ago, following years of research and community pressure over the earthquake-related risks of spills and explosions at the hub, the Legislature mandated that tank owners develop plans to reduce seismic risks. “The state set a very high standard of seismic resilience, but they don’t dictate how a facility has to reach that. Soil-based solutions could be one of many options for these companies,” said John Wasiutynski, sustainability director with Multnomah County, which in 2022 published a study showing a liquefaction-related spill at the Portland hub would be similar to the BP Deepwater Horizon oil spill disaster in the Gulf of Mexico, the country’s largest oil spill to date.Inspired by the study, Portland researchers learned about the microbial method from colleagues at Arizona State University. Other researchers have also launched similar field work, including in Japan and Italy. From lab to fieldLab tests, which use small soil samples and mechanical shakers to simulate earthquakes, have shown that stimulating the growth of microbes and reducing soil saturation even by a few percentage points can significantly reduce liquefaction, Portland researchers said. Khosravifar, Moug and their collaborators are now aiming to prove the method can eliminate liquefaction in the real world, where soil conditions and scale are more complex – as is stimulating earthquakes. Enter the T-Rex, a massive truck outfitted with a mobile shaker that makes artificial earthquakes. The truck, which Portland researchers borrowed from the University of Texas at Austin, got its name from a scene in “Jurassic Park” where the pounding steps of a Tyrannosaurus rex create ripples in a water glass. The T-Rex truck pounds the ground and causes it to shake. The T-rex, a field shaker truck borrowed from the University of Texas at Austin, produces a small earthquake by shaking the ground. In September 2025, Portland State University researchers simulated earthquakes in the field to see if their microbe-focused soil treatment method can prevent the soil liquefying during a mega earthquake.courtesy of Portland State UniversityIn 2019, researchers conducted initial field tests at two sites, one in Northeast Portland near the Columbia River and another in Northwest Portland near the energy hub on the Willamette. They successfully pumped the treatment into fine-grained silt soils at the sites and showed that it desaturated the soils, according to a paper published in 2022 in the Journal of Geotechnical and Geoenvironmental Engineering.They have monitored the Northeast Portland site for six years and have found the treatment is effective for up to five years, Khosravifar said. Throughout August, they retreated the soil at the site, applying the solution to the subsurface soil through a central injection well. Two weeks ago, they installed a giant screw into the ground. The T-rex sat on top of the screw and shook the pile vertically, transferring the shaking energy down into the soil. What they found: The T-rex generated an earthquake – but while mighty, it wasn’t strong enough in deeper soil, Khosravifar said. The researchers are now working on how to increase the shaking intensity, he said, up to a point where the shaking will at least partially liquify the untreated soil and researchers can see the impacts of the treatment in areas injected with the chemicals. “One of the things that remains to be answered is, how much can we really mitigate liquefaction risk? Are we completely eliminating that risk or is it partial?” Khosravifar said. Challenges, drawbacksThe treatment comes with some risks. While the chemicals are benign to humans – calcium nitrate is widely applied to crops as a fertilizer and calcium acetate is a food-grade material used as a preservative in foods and a binder in pharmaceutical pills – the denitrification process, if incomplete, can leave behind nitrates or intermediate compounds like nitrite, nitric oxide or nitrous oxide, Khosravifar said. Nitrous oxide is a potent greenhouse gas. And nitrates or its compounds can contaminate drinking water. Research has linked high nitrate consumption over long periods to cancers, miscarriages and thyroid issues. It is especially dangerous to infants who can develop “blue baby syndrome,” which can be fatal. The formation of gas bubbles in the soil also can reduce porosity and conductivity of soil, potentially affecting water flow. It’s why the soil treatment requires specialized instruments to closely monitor the chemical reaction and nitrate and nitrite levels in groundwater, Khosravifar said. Sensors are embedded in the soil down to 20 feet to give researchers an idea of how the nutrients are moving in soil and whether the chemical reaction is complete. If the method is widely adopted, contractors performing the treatment would be required to use such sensors for long-term monitoring, he said. Other methodsStill, the microbe stimulation method could be a better option when compared to other soil treatments, the researchers said. Some entail injecting bacteria into soil rather than working with existing ones. One of the methods often uses urea, which produces ammonia, a toxic chemical that can damage water quality and is hard to remove.A more established soil improvement approach, known as permeating grouting, calls for injecting microfine cement into the cracks and fissures in liquefaction-prone soils – but it’s emission-intensive, uses a lot of water and is a lot more expensive. Mechanical compaction, another widely used soil treatment method, involves physically packing the soil down tightly so it’s stronger and less likely to shift or collapse during an earthquake.Portland General Electric, for example, used a method that mixed cement into the soil to create stiff, strong columns underground across the Harborton Substation, a major electrical substation in Northwest Portland just west of the energy hub. The project was completed during a rebuild of the substation in 2020 to address soils prone to liquefaction and cost about $40 million, said PGE spokesperson Amber Weyers. The main challenge with such methods is that they require access to the soil. For soils with existing structures or buildings – such as those under the fuel-filled tanks at Critical Energy Infrastructure Hub by the Willamette – there is no good solution. In those cases, PSU’s microbially induced desaturation method may prove the only one feasible, the researchers said.It’s also about a quarter of the cost of many of the other liquefaction prevention solutions, Khosravifar said. For areas occupied by a fuel tank, for example, the nitrate treatment’s initial application would cost $170,000, including the cost of installing wells, he said. Though the chemicals would have to be reapplied every five years, subsequent applications would cost a fifth of the initial expense or about $34,000 every five years, Khosravifar said. Still, the soil treatment is unlikely to be used by homeowners, given that over time it would cost a lot more than the house itself, Khosravifar said. That’s still a fraction of the cost for permeating grouting, which can cost five times as much, or more than $600,000, he said. Moug and Khosravifar said they would like to collaborate with one of the fuel storage companies housed at the Portland energy hub to test and monitor another patch of soil – to better understand how soil and water behave at the hub itself. “We’re not ready to fully implement this solution yet, but it would be a logical next step to test it on site,” Moug said. If you purchase a product or register for an account through a link on our site, we may receive compensation. By using this site, you consent to our User Agreement and agree that your clicks, interactions, and personal information may be collected, recorded, and/or stored by us and social media and other third-party partners in accordance with our Privacy Policy.

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