When it comes to things that give us the heebie-jeebies, parasites reign supreme. However, they are a necessary part of our ecosystems. SAFS assistant professor Chelsea Wood joins Bill Nye on his “Science Rules!” podcast to explain what makes parasites so creepy, how to prevent them from killing us, and why she keeps digging around in decades-old cans of salmon.
The development of small hydropower dams is widespread throughout Brazil and elsewhere in the world, vastly overshadowing large hydropower projects. The proliferation of these smaller dams is a response to growing energy and security needs. Their expansion, however, threatens many of the remaining free-flowing rivers and biodiverse tropical regions of the world—interrupting the migrations of freshwater fishes, on which millions of peoples’ livelihoods depend.
A new University of Washington paper published Jan. 11 in Nature Sustainability quantifies these tradeoffs between hydroelectric generation capacity and the impacts on river connectivity for thousands of current and projected future dams across Brazil. The findings confirm that small hydropower plants are far more responsible for river fragmentation than their larger counterparts due to their prevalence and distribution.
“The cumulative impacts of many small hydropower dams have long been ignored; instead, focus has been on them in isolation, resulting in claims that their impacts are small,” said co-author Julian Olden, a UW professor of aquatic and fishery sciences.
This study was led by Thiago Couto, a recent doctoral graduate in the UW School of Aquatic and Fishery Sciences who is now a postdoctoral researcher at Florida International University.
Dams constrain the movement of migratory fish along river networks and isolate critical habitats, such as spawning and feeding grounds, which may contribute to local extinctions, population declines, and collapses of fishery stocks. This makes migratory fish species some of the most vulnerable organisms to hydropower development in the tropics.
The authors emphasize that many of the migratory fish species impacted by fragmentation are of high ecological and socioeconomic importance, and that some communities may feel the impacts more than others. For example, some small hydropower dams have been linked to the decline of fish stocks that are relied on heavily by Brazil’s Indigenous groups, because fish are no longer reliably migrating through their historic range.
Another concern cited by the authors is that small hydropower dams greatly outnumber large hydropower dams, but their combined energy output is much less. In Brazil, small hydropower plants account for only 7% of total generation capacity even though they represent more than 85% of hydropower plants in the country.
The collective impacts of Brazil’s rapidly growing small hydropower development on river fragmentation and migratory fish species is extensive and shows no signs of lessening as the planned construction of new dams continue, the study explains. It is projected that river fragmentation will increase by 21% in the future, and two-thirds of the 191 migratory species assessed in the study occupy river basins that will experience greater connectivity losses. The authors advocate for improved strategic planning of hydropower development with environmentally informed criteria to minimize the potential adverse ecological effects.
“We were motivated by the hope that society could be smarter about new dam constructions in the future,” said Olden. “The study demonstrates that with careful planning, Brazil can meet future energy production needs with only modest impacts on river fragmentation and migratory fishes.”
This research was funded by an H. Mason Keeler Endowed Professorship from the UW School of Aquatic and Fishery Sciences, the CNPq/Science Without Borders Fellowship, the Rufford Foundation and National Geographic Society. Mathis Messager, who recently earned a master’s at the UW School of Aquatic and Fishery Sciences and is now at McGill University, is also a co-author.
For more information contact Olden, at olden@uw.edu.
Fish populations tend to do better in places where rigorous fisheries management practices are used, and the more measures employed, the better for fish populations and food production, according to a new paper published Jan. 11 in Nature Sustainability.
The study, led by Michael Melnychuk of the University of Washington’s School of Aquatic and Fishery Sciences, draws upon the expertise of more than two dozen researchers from 17 regions around the world. The research team analyzed the management practices of nearly 300 fish populations to tease out patterns that lead to healthier fisheries across different locations. Their findings confirmed, through extensive data analysis, what many researchers have argued for several years.
“In general, we found that more management attention devoted to fisheries is leading to better outcomes for fish and shellfish populations,” Melnychuk said. “While this won’t be surprising to some, the novelty of this work was in assembling the data required and then using statistical tools to reveal this pattern across hundreds of marine populations.”
The research team used an international database that is the go-to scientific resource on the status of more than 600 individual fish populations. They chose to analyze 288 populations that generally are of value economically and represent a diversity of species and regions. They then looked over time at each fish population’s management practices and were able to draw these conclusions:
The study builds on previous work that found, by using the same database, that nearly half of the fish caught worldwide are from populations that are scientifically monitored and, on average, are increasing in abundance. The new paper takes a closer look at specific management actions and how they have impacted fishing pressure and the abundance of each population examined, Melnychuk explained.
“All fish populations have their own unique contexts that might dictate what management tools would be most helpful and promising to use,” he said. “Despite the great diversity in their management objectives and various strategies to meet those, we focused on key management tools in common to many fisheries around the world.”
The international research team chose to look at a spectrum of fish populations, such as hakes in South Africa and Europe, orange roughy in New Zealand, tuna species on the high seas, anchovies in South America and scallops off the Atlantic coast of North America. Most of the populations they examined had a history of being depleted at some point, usually due to historical overfishing.
For example, with U.S. mid-Atlantic population of black sea bass, a rebuilding plan instituted in 1996 brought fishing rates down from three times the sustainable level to below this mark, which led to a steady rebuilding of the fishery and full recovery by 2009.
“Fishers targeting black sea bass in the northeastern U.S. are finally reaping the rewards of harvest caps that allowed the population to rebuild,” said co-author Olaf Jensen of the University of Wisconsin—Madison. “The 2020 catch limit of more than 6,000 tons is the highest since catch limits were first imposed more than 20 years ago.”
This analysis omits fisheries that lack scientific estimates of population status, even though these account for a large amount of the world’s catch. These include most of the fish populations in South Asia and Southeast Asia—fisheries in India, Indonesia, and China alone represent 30% to 40% of the world’s catch, most of which is essentially unassessed. Although fisheries in these regions could not be included in the analyses, the paper’s authors conclude that lessons learned can equally apply to data-limited fisheries: Greater investment in fisheries management systems is expected to lead to better outcomes for the fish populations upon which our fisheries are based.
Other UW co-authors include Ray Hilborn, Trevor Branch, Chris Anderson, Maite Pons, Daniel Hively, Charmane Ashbrook, Nicole Baker, and Ricardo Amoroso. A full list of paper co-authors is available in the paper.
This research was funded by The Nature Conservancy, The Wildlife Conservation Society, the Walton Family Foundation, and a consortium of Seattle fishing companies.
For more information, contact Melnychuk at mmel@uw.edu.
“You are what you eat.” Turns out, the same can be said for bears.
Researchers from the University of Washington recently assessed the contribution of salmon to the diet of brown bears in Southwest Alaska. Their findings confirmed that while the bears are reliant on large seasonal salmon runs, they also eat a variety of other foods, including both vegetation and fauna. The research results were published November 5 in the online issue of the Journal of Fish and Wildlife Management.
“Individual brown bears vary greatly in foraging patterns,” said lead author Hyejoo Ro, a recent BS graduate from the UW School of Aquatic and Fishery Sciences (SAFS). “A majority do tend to eat a lot of salmon, but there are also bears that seem to consume more terrestrial food items, such as moose, vegetation, and berries.” Ro’s published work is the culmination of her undergraduate capstone project.
Bristol Bay is home to one of the world’s largest sockeye salmon runs, which provides a vital nutrient source for the watershed and the region’s large brown bear population and also supports a thriving commercial fishery.
Researchers with the Alaska Salmon Program have routinely collected bear hair along the tributaries of Lake Aleknagik in Southwest Alaska. Previous research, as well as field observations of bear behavior and droppings, shows bears are selective in their consumption of salmon (prioritizing feeding on certain nutrient-rich parts of the fish), while also eating other food items. However, researchers wanted to know if individual diets could be indicative of whether some bears in the area were dominant (the assumption being that dominant bears would be more competitive and have a higher ratio of salmon in their diets).
An initial DNA analysis of the hair samples distinguished between individual bears over a four-year span. Next, individual bear samples underwent an isotope analysis to identify certain dietary signatures. Samples were then matched with available food items collected from the local environment, including sockeye salmon and various berries.
One of the most challenging aspects of this process was determining how long it takes for a bear’s diet to work its way into the animal’s individual hairs and become detectable.
Co-author Jennifer Stern, a graduate student at SAFS, studies the diet of wild polar bears using hair samples and faces the same problem. To address this question, she uses observations and analysis of zoo polar bear hair to provide an estimation of how long it takes for both the hair growth rate and for isotopic signatures to show up in hair. However, assessing samples from wild brown bear populations remains challenging because of the possibility of sampling hair from the current and previous year.
“The timing of hair sample collection makes it difficult to fully determine the seasonality of brown bear diets,” said Ro. “Since collection occurred during the summer when the bears are molting old fur and growing new fur, the isotopic signature is very different, depending on whether we analyzed old or new hairs.”
The team’s results illustrated that bears in the area opportunistically fed at different trophic levels (position on the food chain), despite the abundance of salmon and the possibility of dominant bears being a limiting factor in food choice.
Studying the feeding habits of Alaska’s brown bears can help researchers to understand the ecosystem as a whole and learn how seemingly distinct components are related. From a management perspective, the wide-ranging impacts that salmon have on this ecosystem are tied to their sustainability as a resource.
“There are a lot of bears in the area, and like the fishery, they need the salmon to sustain their livelihood,” said Ro. “Getting a better idea of how reliant bears are on sockeye salmon can give a better perspective on how to share this fishery.”
This research was funded in part by the Richard and Lois Worthington Endowment and the Mary Gates Endowment Research Scholarship.
For more information, contact Ro at hr27@uw.edu.
Coral reefs serve important ecological functions, from providing habitat for countless species to protecting shorelines from erosion. Reef-dependent fisheries are also a vital source of food and income for hundreds of millions of people in tropical island nations where coral reefs are valued at $6.8 billion annually.
The pressing concerns of climate change have placed the long-term health of the world’s coral reefs in jeopardy. However, new research inspires hope as some corals managed to survive a recent and globally unprecedented heatwave.
“Understanding how some corals can survive prolonged heatwaves could provide an opportunity to mitigate the impact of marine heatwaves on coral reefs, allowing us to buy time as we work to limit greenhouse gas emissions,” said lead author Danielle Claar, a postdoctoral researcher at the University of Washington who completed the work as doctoral student at the University of Victoria.
Heat stress from the 2015–2016 El Niño event triggered mass coral bleaching and mortality on reefs around the world. The study published Dec. 8 in Nature Communications presents the discoveries made by an international research team as they tracked hundreds of coral colonies on reefs around Christmas Island (Kiritimati) in the Pacific Ocean, where the heatwave lasted an unprecedented 10 months.
Climate change threatens the world’s coral reefs because corals are highly sensitive to the temperature of their surrounding waters. Warmer waters can trigger a coral bleaching where the coral turns white as it expels the symbiotic food-producing algae living in its tissues. Prolonged bleaching events often cause corals to die from starvation, but they can recover if they reclaim their food source within a few weeks.
To date, coral recovery from bleaching has only ever been observed after heat stress subsides. With global climate models predicting that heatwaves will continue to increase in both frequency and duration, a coral’s ability to recover its food source during a prolonged heatwave is essential to its survival.
Researchers showed that corals only exhibited this capacity if they were not also exposed to other types of human-caused stressors, such as water pollution. This affirms that local reef management could help improve corals’ chances of surviving climate change.
“We’ve found a glimmer of hope that protection from local stressors can help corals,” said Julia Baum, a University of Victoria marine biologist and the study’s senior author.
“Although this pathway to survival may not be open to all corals or in all conditions, it demonstrates an innovative strategy for survival that could be leveraged by conservationists to support coral survival,” said Claar.
The research was supported by the Natural Sciences and Engineering Research Council of Canada, the U.S. National Science Foundation, the David and Lucile Packard Foundation, The Pew Charitable Trusts’ Pew Fellows Program in Marine Conservation, the Rufford Foundation, the Canadian Foundation for Innovation and the Shedd Aquarium.
For more information, contact Claar at danielle.claar@gmail.com
Adapted from a University of Victoria news release.
An area in the Olympic Peninsula’s Hoh Rain Forest in Washington state for years held the distinction as one of the quietest places in the world. Deep within the diverse, lush, rainy landscape the sounds of human disturbance were noticeably absent.
But in recent years, the U.S. Navy switched to a more powerful aircraft and increased training flights from its nearby base on Whidbey Island, contributing to more noise pollution on the peninsula—and notably over what used to be the quietest place in the continental U.S. While local residents and visitors have noticed more aircraft noise, no comprehensive analysis has been done to measure the amount of noise disturbance, or the impact it has on people and wildlife.
Now, as the Navy is set to implement another increase in flight activities, a University of Washington study provides the first look at how much noise pollution is impacting the Olympic Peninsula. The paper found that aircraft were audible across a large swath of the peninsula at least 20% of weekday hours, or for about one hour during a six-hour period. About 88% of all audible aircraft in the pre-pandemic study were military planes.
“I think there is a huge gap between what the Navy is telling people—that its aircraft are not substantially louder and operations haven’t changed—and what people are noticing on the ground,” said lead author Lauren Kuehne, who completed the work as a research scientist at the UW School of Aquatic and Fishery Sciences and is now an independent consultant. “Our project was designed to try and measure noise in the ways that reflect what people are actually experiencing.”
The study was published Nov. 25 in the journal Northwest Science.
The Navy is set to implement a 75% increase in air activities over the Olympic Peninsula, a place that is historically, culturally, and ecologically significant. Eight American Indian tribes call the peninsula home, while Olympic National Park receives more than 3 million visitors a year and is a UNESCO World Heritage Site. More than two dozen animal species are found only on the peninsula, and multiple species are listed as threatened or endangered under the federal Endangered Species Act.
“The Olympic Peninsula is a renowned hotspot for wildlife, home for people of many different cultures, and a playground for outdoor enthusiasts,” said co-author Julian Olden, professor at the UW School of Aquatic and Fishery Sciences.
The researchers chose three primary sites on the Olympic Peninsula to monitor the soundscape during four seasonal periods from June 2017 to May 2018. Two sites, at Third Beach and Hoh Watershed, were near the coast, while the third site was inland on the Hoh River Trail. They placed recorders at each site to capture sound continuously for 10 days at time, then recruited and trained volunteers to help process the nearly 3,000 hours of recorded audio.
“This data is very accessible—you can hear and see it, and it’s not rocket science,” Kuehne said. “I wanted people to feel like they could really own the process of analyzing it.”
From their analysis, the researchers identified nearly 5,800 flight events across all monitoring locations and periods. Of these, 88% were military aircraft, 6% were propeller planes, 5% were commercial airplanes and less than 1% were helicopters. Three-quarters of all recorded military aircraft noise occurred between 9 a.m. and 5 p.m. on weekdays. Most of the military aircraft were Growlers, or Boeing EA-18G jets that are used for electronic warfare drills that resemble “hide and seek” with a target.
The researchers found that most of the aircraft noise was intermittent, detectible across all the sites that were monitored simultaneously, and followed no set pattern. The noise mostly registered between 45 and 60 decibels, which is comparable to the air traffic sounds in Seattle, Kuehne said. Occasionally, the sound level would hit 80 decibels or more, which is akin to the persistent noise when walking under Seattle’s former waterfront viaduct.
Conversations with local residents also revealed a majority who notice the low-level jet noise, the researchers said. The chronic and unpredictable nature of the noise is especially tiresome for residents, and some report difficulty sleeping, learning in school, and even interference with hearing aids.
Previous research has shown that loudness is only one aspect of how sound can impact human health. Studies have found that the duration of noise, unpredictable patterns, and the inability to control exposure all contribute to stress, annoyance, sleep disturbance, and interference with learning.
Noise impacts on wildlife are less studied, but some research has shown it can prompt physiological stress and impact animals’ ability to reproduce successfully. Noise can also interfere with how animals communicate and find prey.
“The deafening sound of anthropogenic noise not only threatens wildlife but may also deter people from visiting in the future,” Olden said. “Why travel to the Olympic Peninsula to only experience noise comparable to Seattle?”
The researchers hope these results will prompt follow-up assessments of how chronic aircraft noise impacts residents on the peninsula. They also hope the Navy will publicly acknowledge the extent of its noise pollution and consider changing its operations near the peninsula.
“My wildest-dream scenario is that this would allow the Navy to take seriously people’s requests that they move at least some of the training elsewhere, to other military operations areas,” Kuehne said.
This research was funded by The Suquamish Foundation, the One Square Inch of Silence Foundation, and the UW School of Aquatic and Fishery Sciences.
For more information, contact Kuehne at lauren.kuehne@gmail.com and Olden at olden@uw.edu.
More images are available to download here.
Coral reefs are among the most diverse ecosystems in the world, protecting coastlines from erosion and supporting more than 500 million people through tourism and fishing livelihoods. But at the current rate of global warming, mass coral bleaching is expected to become more frequent and severe worldwide.
Coral bleaching is a significant problem for the world’s ocean ecosystems: When coral becomes bleached, it loses the algae that live inside it, turning it white. Corals can survive a bleaching event, but while they are bleached they are at higher risk for disease and death.
Now an international consortium of scientists, including a coral researcher from the University of Washington, has created the first-ever common framework for increasing comparability of research findings on coral bleaching. The work, described in a paper published Nov. 21 in the journal Ecological Applications, provides a common language and reference points for researchers to compare results across studies.
“It is very important to find better and more efficient ways to perform experiments that can help us to understand the vulnerability, tolerance, and resilience of these ecosystems,” said co-author Jacqueline Padilla-Gamiño, an assistant professor in the UW School of Aquatic and Fishery Sciences who studies coral physiology and reproduction. “Our work will provide an incredible platform that scientists around the world can use to develop more open and collaborative science.”
The framework covers a broad range of variables that scientists generally monitor in their experiments, including temperature, water flow, light and other factors. It does not dictate what levels of each should be present during an experiment into the causes of coral bleaching; rather, it offers a common framework for increasing comparability of reported variables.
“Coral bleaching is a major crisis, and we have to find a way to move the science forward faster,” said lead author Andréa Grottoli, professor of earth sciences at The Ohio State University.
The consortium leading this effort is the Coral Bleaching Research Coordination Network, an international group of coral researchers. Twenty-seven scientists, representing 21 institutions around the world, worked together as part of a workshop at Ohio State in May 2019 to develop the common framework.
The goals are to allow scientists to compare their work, make the most of the coral samples they collect, and find ways to create a common framework for coral experimentation.
Their recommendations include guidelines for experiments that help scientists understand what happens when corals are exposed to changes in light or temperature over a short period of time, a moderate period, and long periods. The guidelines include a collection of the most common methods used for recording and reporting physical and biological parameters in a coral bleaching experiment.
“Reefs are in crisis,” Grottoli said. “And as scientists, we have a responsibility to do our jobs as quickly, cost-effectively, professionally, and as well as we can. The proposed common framework is one mechanism for enhancing that.
That such a framework hasn’t already been established is not surprising: The scientific field that seeks to understand the causes of and solutions for coral bleaching is relatively young. The first reported bleaching occurred in 1971 in Hawaii; the first widespread bleaching event was reported in Panama and was connected with the 1982–83 El Niño.
But experiments to understand coral bleaching didn’t really start in earnest until the 1990s—and a companion paper by many of the same authors found that two-thirds of the scientific papers about coral bleaching have been published in the last 10 years.
Researchers are still trying to understand why some coral species seem to be more vulnerable to bleaching than others, and setting up experiments with consistency will help the science move forward more quickly and economically.
“We’d be able to better collaborate, and to build on one another’s work more easily. It would help us progress in our understanding of coral bleaching—and because of climate change and the vulnerability of the coral, we need to progress more quickly,” Grottoli said.
Other paper co-authors are from University of Hawaii at Mānoa, Florida Institute of Technology, University of Delaware, Texas A&M University, Pennsylvania State University, University of North Carolina at Chapel Hill, University at Buffalo – State University of New York, John G. Shedd Aquarium, Oregon State University, Duke University, University of Alabama at Birmingham, University of Southern California, Smithsonian Tropical Research Institute, U.S. Geological Survey, University of Technology Sydney, National Oceanic and Atmospheric Administration, Stanford University, and University of Konstanz.
This work was funded by the National Science Foundation.
Adapted from an Ohio State news release.
The University of Washington School of Aquatic & Fishery Sciences is hiring a Diversity Specialist—this temporary position will be 9 months at 50% FTE, including benefits, and will report to the Manager of Student Services & Diversity.
The SAFS Diversity Specialist will fill a key role in the School’s ongoing efforts to become an equitable, inclusive, and welcoming academic and professional institution for students, staff, faculty, and colleagues. This includes leading and supporting efforts to attract, engage, and retain diverse and underrepresented groups at all levels and ranks, and to build strategic partnerships covering the academic, professional, and cultural breadth of communities connected to aquatic and fishery sciences.
The Diversity Specialist will be key in providing the School with expert knowledge and educational resources; community building and retention; outreach and recruitment; assessment and evaluation; and visioning and strategic planning related to diversity, equity, and inclusion (DEI) principles in STEM.
For more information and to apply, visit the listing here or go to https://hr.uw.edu/jobs/ and search for Req# 184870. The position will remain open until filled—application review will begin in mid-December.
The global pandemic is hurting the seafood industry, and American fishmongers may flounder without more government aid, according to the largest study of COVID-19’s impacts on U.S. fisheries.
The new study, published Nov. 23 in the journal Fish and Fisheries, found that monthly fresh seafood exports declined up to 43% compared to last year, while monthly imports fell up to 37%, and catches dropped 40% in some months.
Additionally, over the first six months of 2020, total U.S. seafood exports were down 20% and imports were down 6%, compared to the same period last year. Further losses are likely as restrictions increase to address COVID-19.
“Seafood has been hit harder than many other industries because many fisheries rely heavily on restaurant buyers, which dried up when the necessary health protocols kicked in,” said lead author Easton White of the University of Vermont. “Restaurants represent about 65% of U.S. seafood spending, normally.”
For context, over one million U.S. seafood workers regularly produce more than $4 billion in annual exports, much of which is processed overseas and imported back to the U.S.
While seafood data often takes several months—or longer—to compile, the research team, including Trevor Branch of the University of Washington, used pioneering methods to quickly determine the pandemic’s impacts on fisheries. U.S. Congress received preliminary data from the study in September.
The researchers found that in January 2020, demand for American imports plummeted as lockdowns began in China. Starting in March, web searches for U.S. seafood restaurants fell over 50%, and foot traffic at seafood markets decreased 30%.
Aid for fisheries has been slow, partly because pandemics are not currently considered valid reasons for a fishery failure or disaster under current law. The CARES act has authorized $300 million for the sector.
Even with increased demand for seafood delivery, which surged 460% for Google searches from March to April, some producers may not be able to recover without government assistance.
“Seafood is a seasonal business,” said White. “If you have a March to June season, and can’t get funds until next year, you might have to quit. Support from policymakers will decide which producers can survive.”
Aid should target regions where fisheries make up a disproportionate share of the economy, including in Maine, Alaska, Louisiana, and Washington, as well as tribal fisheries, the researchers said.
“COVID-19 is a huge risk to the big factory boats that both catch and process fish in our waters—this combines the worst risks of cruise ships and meat plants. Their workers need priority access to the new vaccines,” said Branch, associate professor in the UW School of Aquatic and Fishery Sciences.
“Foreign markets play an important role in the U.S. seafood sector, but dependence on exports leaves portions of the sector vulnerable to these global shocks,” added co-author Jessica Gephart of American University. “Diversifying the sector by building local networks and consumer education campaigns can help build resilience to future shocks.”
The study used traditional and novel sources of data, from NOAA fisheries reports and federal customs data, to anonymous commercial web location data made available to researchers studying COVID-19, and a comprehensive database of news and trends—created by University of Vermont students—tracking the pandemic’s impacts on fisheries, from plant closures and outbreaks to travel restrictions on seafood laborers.
While the drops in catches and international trade were stark, the researchers said some seafood producers have found ways to adapt. Community supported fisheries programs are increasing, with websites like Local Catch helping consumers buy fresh seafood that might have previously been sold to restaurants or at markets.
That said, home cooking won’t replace seafood restaurant sales.
“Most people who cook at home are not likely looking to cook fresh monkfish from Maine for themselves or their family, so the types of species being consumed is changing,” said co-author Halley Froehlich of University of California, Santa Barbara.
These changes in seafood consumption may be here to stay—particularly as global COVID-19 cases climb ever higher—as producers look for ways to sell more of their catches domestically.
Other co-authors are Richard Cottrell of the University of California, Santa Barbara; Rahul Agrawal Bejarano of the University of Michigan; and Julia Baum of University of Victoria.
This study was funded by COVID-19 rapid research funding from the Gund Institute for Environment at University of Vermont.
This piece was adapted from a University of Vermont news release.
Throughout the animal kingdom there are many advantages to migrating in large numbers. One such benefit is “collective navigation,” where the social interactions among animals improve the group’s ability to find its way.
A new University of Washington study has found that Chinook salmon seem to use collective navigation and interact socially to help each other find fish ladders at dams. The findings were published on Oct. 21st in the Proceedings of the Royal Society B.
Salmon migrating upriver often encounter blockages and obstructions they need to circumvent. The implementation of fish ladders alongside large dams have provided salmon with a way to forge ahead, though they still face the challenge of locating, entering, and traversing these fishways.
Researchers analyzed the spawning migrations of adult Chinook and sockeye salmon in the Columbia River Basin from 2013–2014. They found that Chinook salmon were able to navigate fish ladders more quickly on days when there were more Chinook present.
“Large groups of fish appear to have an easier time finding the entrances to fish ladders and passing through them,” said Connie Okasaki, a doctoral student in Quantitative Ecology and Resource Management. “We take that to mean some sort of collective behaviors are at play.”
While larger groups of Chinook may have a navigational advantage, by contrast, sockeye salmon seem to neither help nor hurt each other during migrations. Ironically, this may be because sockeye tend to be more social and form very tight knit schools.
“It appears that sockeye are almost too social; they’re acting as a unit, as if the group were a single individual acting alone,” says Okasaki. “Whereas Chinook form much looser aggregations in which the whole community present at the dam is trying to navigate and help each other.”
The study suggests that changes in population could be magnified in Chinook salmon due to this behavior: large, healthy populations of salmon should have an easier time staying healthy, while small struggling populations will have a harder time maintaining their numbers. The migration gets more difficult when there is a smaller “team” to help out.
Salmon runs, particularly those in the Columbia River, face many challenges. These new insights into how salmon migrate using collective navigation have the potential to become key components in management decisions.
“Salmon are a stunning example of perseverance as they make the difficult journey upstream. The idea that that journey may also involve teamwork, humanizes these fascinating creatures further and only adds to their charismatic appeal,” said Okasaki.
Other co-authors are Matthew Keefer of the University of Idaho; Peter Westley of the University of Alaska Fairbanks; and Andrew Berdahl, UW professor of aquatic and fishery sciences. This research is based upon work supported by the NSF-GRFP under Grant No. DGE-1762114.
For more information, contact Okasaki at cokasaki@uw.edu.
Related story: Early-arriving endangered Chinook salmon take the brunt of sea lion predation on the Columbia