Bottom trawling catches thousands of fish species, including those most at-risk
From seahorses to sharks, more than 3,000 fish species have been caught in bottom trawls, including many at risk of extinction, according to a new global inventory.
More than 3,000 fish species have been caught in bottom trawls, with estimates suggesting the true number could be nearly double, according to the world’s first global inventory.
Published in Reviews in Fish Biology and Fisheries by researchers at the University of British Columbia (UBC), the study draws on more than 9,000 records of fish species reported in bottom trawls from 1895 to 2021.
“This is the clearest picture we’ve had of the breadth of bottom trawling. It reveals just how many species are being caught, and how much we have been missing,” said first author Dr. Sarah Foster, senior researcher and program leader at UBC’s Project Seahorse.
Extinction risk in the net
Bottom trawling drags heavy nets across the seafloor, sweeping up most marine life and habitats in its path. It is one of the most widespread and destructive fishing practices. Yet very little is known about what species are caught and how catches affect marine biodiversity.
We can’t manage what we don’t know. When we remove thousands of species without understanding the impacts on their wild populations, we risk destabilizing the very systems that fisheries depend on,” added Dr. Foster.
The study found that one in seven fish species recorded in bottom trawl catches with assigned conservation status are threatened or near threatened with extinction, based on the International Union for Conservation of Nature (IUCN) Red List, the global standard for assessing extinction risk.
One in four reported fish species are classified as either data deficient, where not enough information is available for a conservation assessment, or have not been evaluated, which means a large portion of bottom trawling is operating in an information vacuum.
Among the species recorded are the critically endangered giant guitarfish, the endangered zebra shark, and at least three vulnerable seahorse species.
The data also shows that bottom trawls catch all or most species in some fish families. These include both the ocean’s most nutritious and commercially critical fishes, such as jacks and croakers, and rare, distinct groups such as giant guitarfish and plough-nosed chimera.
“Bottom trawling sweeps up entire branches from the marine tree of life. It does not discriminate between common species and those already on the brink of extinction. From critically endangered giant guitarfishes to vulnerable plough-nosed chimeras and seahorses, we put pressure on evolutionarily unique species, including many we still know too little about,” said co-author Syd Ascione, a research biologist at Project Seahorse.
More than trash
The study also found that smaller fish species are often not recorded at all and are likely being grouped under vague categories such as “trash fish” or “mixed fish,” hiding the true number of species being caught. Additionally, where this information was reported, approximately 95 per cent of the species were not being targeted by the fisheries yet 64 per cent were kept anyway.
Together, the researchers say the findings suggest that what is recorded is only a glimpse of the true toll bottom trawling has on marine ecosystems – and highlight the urgent need to rethink how bottom trawl catches are documented, assessed and managed.
A call to action
Nearly 99 per cent of bottom trawling takes place within countries’ national waters and jurisdictions, meaning governments have both the authority and responsibility to manage impacts on biodiversity and fisheries.
“We allow at least 100,000 trawlers to scrape the ocean floor, without even knowing what they are catching, and what damage they are doing to those species. It is important that governments take a precautionary approach and exclude bottom trawling from large swathes of the ocean, and particularly from so-called marine protected areas.” added senior author Dr. Amanda Vincent, director of Project Seahorse.
The critically endangered giant guitarfish is among the species being caught by bottom trawling, according to a new global inventory published by University of British Columbia researchers (Sarah Foster, University of British Columbia)
Seahorse species designated as vulnerable by the International Union for Conservation of Nature are among the bycatch being captured by bottom trawling, according to a new global inventory published by University of British Columbia researchers (Sarah Foster, University of British Columbia)
A Call for Cooperation in the Southwest Atlantic Ocean
The Southwest Atlantic Ocean is one of the most productive and ecologically important marine regions on the planet. Stretching from northern Brazil to the southern tip of South America, the region hosts a remarkable combination of ocean currents, ecosystems, and species that support both global biodiversity and major fisheries. Yet despite its immense importance, the region remains one of the few large ocean areas without a coordinated system for managing its shared marine resources. A new international study, led by researchers at UBC’s Institute for the Oceans and Fisheries (IOF), calls for stronger cooperation among countries in the region to ensure the long-term sustainability of its ecosystems and fisheries particularly under climate change.
The Southwest Atlantic Ocean.
The economic importance of these fisheries is enormous. Fisheries in the Southwest Atlantic employ nearly 900,000 people and produce around two million tonnes of catch each year, valued at approximately five billion dollars. These fisheries support coastal economies across Brazil, Uruguay, Argentina, and other neighbouring regions, providing jobs, food security, and export revenue. However, the ocean does not recognize national borders, and many of the species that sustain these fisheries migrate across multiple jurisdictions throughout their life cycles. Fish, shrimp, and squid stocks often move seasonally between different parts of the region and the local high seas, linking ecosystems and economies.
Because of this connectivity, effective management of marine resources requires cooperation between countries. However, despite bilateral agreements and various scientific collaborations, there is still no dedicated regional body responsible for coordinating fisheries and ocean governance across the entire Southwest Atlantic. “The Southwest Atlantic Ocean is a region of incredible ecological and economic importance, yet it lacks a comprehensive governance framework that brings countries together to manage shared resources,” said Dr. Juliano Palacios-Abrantes, postdoctoral fellow at IOF and lead author.
Squid. Image by Falco/Pixabay
“Climate change is fundamentally altering the ocean,” said Brazil-based researcher Dr. Palacios-Abrantes. “Species are moving, ecosystems are shifting, and fisheries are changing as a result. These changes are happening across borders, which means countries must work together to respond effectively.”
Another growing concern in the region is the presence of distant-water fishing fleets operating near the edges of national jurisdictions. These fleets often target valuable species, such as squid and tuna, and compete directly with local fishing industries. In some cases, vessels exploit regulatory gaps or operate in areas where enforcement is limited. Illegal, unreported, and unregulated fishing further complicates management efforts, allowing vessels to move between jurisdictions and evade oversight. These challenges highlight the need for stronger regional cooperation to ensure that fisheries remain sustainable and equitable.
Effective ocean management also depends on reliable data, yet large gaps remain in scientific knowledge about the region’s ecosystems and fisheries. Small-scale fisheries, which play a crucial role in coastal livelihoods across Latin America, are often poorly documented. In Brazil, for example, national fisheries monitoring programs have experienced disruptions over the past decade, leaving researchers and policymakers with limited information about catch levels and stock conditions. These data gaps make it harder to track changes in marine ecosystems and design effective conservation measures.
Paraty, Brazil. Image by Clara TCHOUBÉ / Pixabay
The timing may also be favourable for advancing new governance initiatives. Brazil is set to host several major international environmental meetings in the coming years, including global climate and ocean conferences that will bring international attention to marine sustainability. These events create opportunities for countries in the region to strengthen cooperation and develop new strategies for managing fisheries and protecting biodiversity.
“The ocean connects our countries, ecosystems, and communities,” Palacios-Abrantes said. “If we want to safeguard the future of the Southwest Atlantic, cooperation will be essential. The challenges we face are shared, and the solutions must be shared as well.”
Integrated ocean governance is needed in the Southwest Atlantic Ocean to foster fisheries, conservation and resilience to climate change, was published in Discover Ocean, and authored by Juliano Palacios-Abrantes and an international team of researchers from institutions across Argentina, Brazil, and Uruguay.
Tags: Argentina, Atlantic, Brazil, climate change, CORU, ecosystems, fish, fish catch, fisheries economics, fisheries management, fishing fleets, industrial fishing, IOF postdoctoral fellows, Juliano Palacios-Abrantes, marine ecosystems, regional governance, shrimp, small-scale fisheries, South America, Southwest Atlantic Ocean, squid, temperatures, Uruguay, whales
Aquaculture is shifting toward less sustainable species: new UBC study
While aquaculture has grown rapidly to meet global seafood demand, it is increasingly relying on species that are less beneficial for food security, climate mitigation, and biodiversity, said a new study from researchers at the University of British Columbia.
Integrated seaweed and abalone farm in Xiamen, China. Photo credit: William Cheung
“Aquaculture has enormous potential to support global food systems and environmental goals, but our findings show that current production trends are moving us in the wrong direction,” said Dr. William Cheung, professor and Director of the Institute for the Oceans and Fisheries (IOF), and senior author of the study. “We’re seeing a growing mismatch between what we produce and what would best support climate, biodiversity, and food security outcomes.”
Fish farming (Norway) Image by Tapani Hellman from Pixabay
The study developed indices that measured how aquaculture production contributes to food, climate, and biodiversity goals, along the UN Sustainable Goals agenda. They noted that China, for example, accounted for 56 per cent of global aquaculture production in 2022, yet its production mix showed declines across all three indices between the 1976–1980 baseline and 2019–2023: −14.1 per cent for food, −21.6 per cent for climate, and −12.9 per cent for biodiversity. In the Americas, the food index increased only marginally (+0.8 per cent), while the climate and biodiversity indices declined by 11.4 per cent and 9.1 per cent, respectively.
“Salmon aquaculture is currently the fastest-growing food sector in the world however, it is strongly affected by warming waters and deoxygenation, and is a species that has lower FCB potential,” said Aleah Wong, lead author and PhD candidate in the IOF. “Not all aquaculture species are equal. Some, like bivalves and seaweed, can deliver significant environmental benefits, while others come with higher trade-offs,” she said. “Currently, many of the most beneficial species are under-represented in global production.”
“Food security is shaped by factors like production efficiency and species’ nutrient density, but also by complex dynamics between producers, consumers, markets and regulatory bodies that affect food security indirectly through impacts on food availability, access, trade, income and equity,” said Dr. Cheung. “Many regions already farm species with high sustainability potential. By scaling up these species and diversifying production, aquaculture can better contribute to global sustainability targets.”
Mussel (bivalve) farming. Photo by Jacek Kijewski from Pixabay
“Shifting toward more sustainable aquaculture would require coordinated international action,” said Wong. “Better policies, investment in innovation, and changes in what consumers are willing to eat need to be made.”
The study underscored that the future of aquaculture depends not only on how much is produced, but on what is produced—and how those choices align with global environmental and food system goals.
“Shifting Trends in Aquaculture’s Biological Potential to Address Food, Climate and Biodiversity Challenges” was published in Fish and Fisheries.
Thousands of jellyfish clones are multiplying in B.C. lakes
If you spot a jellyfish in British Columbia, chances are you are not looking at an ocean drifter. You might be standing at the edge of a lake, watching a thumbnail-sized freshwater, nearly transparent medusa pulse just beneath the surface, something that feels almost unreal the first time you see it. It is the kind of sight that feels like a mistake, until it happens again, and again, in more places.
That is the strange reality exposed by a recent study led by UBC Institute of Ocean and Fisheries researchers Dr. Florian Lüskow and Dr. Evgeny Pakhomov. Pulling together decades of sightings, the team examined how the invasive peach blossom jellyfish has been appearing across B.C., and why those appearances may become more common as summers warm. The species, originally from China, has been reported in B.C. since 1990, and it has now been documented in at least 34 locations in the province, making it the northernmost known range for this species in North America.
What makes this story more than just a curiosity and how easy it is to miss. “This is an introduced jellyfish species from China which has spread around the world. We know very little about how they affect ecosystems and biodiversity of these systems in Canada, because the research hasn’t been done yet,” Dr. Lüskow said. The concern is not about human safety; these jellyfish are not harmful to people, but about what they could do to freshwater ecosystems if they appear more often or in more lakes.
At first glance, the medusa stage is the easiest part to notice, when small jellyfish seen in late summer, floating and pulsing in the water column. However, the visible stage is only one chapter of the species’ life cycle. The other key stage is the polyp, a tiny bottom-dwelling form that can live undetected and produce medusae only when conditions are right.
“Polyps are very small, usually around a millimetre in size, and it is challenging to locate them,” Dr. Pakhomov explained. He added that polyps can inhabit shallow areas attached to rocks and submerged wood debris. The researchers and citizens often realize the species presence once medusae appear in warm waters. In other words, a lake can host the jellyfish long before anyone sees a single medusa.
Temperature appears to be the gatekeeper. In the team’s observations, the medusa form appears only when water temperatures exceed about 24°C, and in B.C. the medusae are typically seen between July and early October. This detail matters because climate change is pushing conditions toward warmer summers and milder winters, which may increase the number of lakes that cross the threshold for medusa production. Dr. Lüskow noted that B.C. sits at the northern edge of the species’ current range, and mild winters and high summer temperatures help determine whether the jellyfish can reproduce.
There is a twist that makes this invasion even stranger: every jellyfish examined in B.C. so far has been male and genetically identical. In other words, they are clones. This suggests the population may be spreading through asexual reproduction from a shared source, likely linked to polyps that persist and produce medusae when conditions allow. Dr. Pakhomov also notes that because only males have been found, the jellyfish may not be able to complete sexual reproduction in B.C., which could limit how well they adapt to new environments. However, clonal persistence, combined with warming and accidental transport, could still allow the species to keep appearing.
How they move between lakes is also not pinned to a single pathway. The researchers discuss likely routes such as polyps being transported on recreational boats or moved by birds. The team also observed a habitat pattern: jellyfish were found in ponds, quarries, and lakes, but not in creeks or rivers.
For the researchers, the next steps are practical and urgent. Dr. Pakhomov describes two priorities: mapping the true distribution and range of peach blossom jellyfish in B.C., and quantifying their impacts on freshwater ecosystems, including possible effects on young salmon. Dr. Lüskow points to environmental DNA as a promising tool, because it could detect presence even when medusae are not visible.
Freshwater jellyfish can feel like a curiosity, the kind of thing you mention because it sounds impossible. This study suggests that they are also a signal, a reminder that freshwater ecosystems are changing, sometimes quietly, and that the first step toward responding is knowing what is already there.
The study, Brazil’s Invisible Invaders: Are Craspedacusta jellyfish a ticking ecological bomb?, was conducted by an international team of researchers, including UBC Institute for the Oceans and Fisheries scientists Florian Lüskow and Evgeny Pakhomov.
Tags: British Columbia, Evgeny Pakhomov, faculty, florian Luskow, IOF alumni, IOF postdoctoral fellows, jellyfish, lakes
Zara Maria Carlota das Minas Gerais (AKA Lota)
Living the island life
Owns Juliano Palacios Abrantes, Postdoctoral Fellow
Seals risk death by polar bear for a varied meal, UBC study finds
Arctic tracking shows ringed seals trade safety for food variety—evidence that conservation plans must factor in both food and fear.
Polar bear. Photo credit: Dr. Katie Florko.
As climate change reshapes Arctic food webs, ringed seals will swim into risky polar bear territory if the menu is varied enough.
That’s the central finding of a new study published in Ecology Letters. UBC researchers tracked 26 ringed seals and 39 polar bears in eastern Hudson Bay, using GPS and dive information to analyze how the animals found, and avoided becoming, food.
“Climate change is reshaping the Arctic, an area often seen as a foreshadowing of climate changes around the world,” said lead author Dr. Katie Florko, who conducted the research as a doctoral student at UBC’s Institute for the Oceans and Fisheries (IOF). “It’s not just melting sea ice: climate change is affecting everything: the predators, the prey and their habitats, effectively reshuffling a complex, intertwined system. If we map critical habitat while ignoring how bears and seals interact, we risk potentially protecting areas that animals are actually avoiding in a climate-changed future.”
“Communities across the North rely on healthy seal and fish populations, so more accurate maps of these populations also help support food security and wildlife management,” said senior author Dr. Marie Auger-Méthé, UBC professor in the department of statistics and IOF.
A ringed seal in the ocean. Photo credit: Dr. Marie Auger-Methe.
A mix of food outweighs fear
Dr. Florko’s team combined GPS data with daily sea-ice maps and yearly models of the mix of fish species available in Hudson Bay, following where seals and bears went, how seals moved and dived, and what the fish buffet looked like beneath them. Feeding these data into ecological models, they identified how the seals reacted to the bears’ presence, or their ‘landscape of fear’.
They found something surprising: while seals avoided spots where bears were very active—moving through them quickly—they rolled the dice and dived for longer when the fish mix was especially varied. This was true even in bear hotspots. In safer places, however, greater fish variety meant shorter dives, likely because food was easy to get.
The researchers theorize this could be due to the ‘portfolio effect’. Just as investors have many different investments to reduce overall risk, animals select varied food sources to increase their chances of finding something to eat in ever-changing ocean conditions. “The seals aren’t putting all their fish in one basket,” said Dr. Florko.
Dr. Florko located the bears from the air by helicopter, waiting for a ranger to shoot a tranquilizing dart, before landing to clip the GPS collars on. “They smelled like a big wet dog.”
Listening for paws on the ice
The research also suggests that ringed seals may have tactics for identifying high-traffic polar bear areas. Dr. Florko looked into whether seals might listen for bears walking on the ice while the animals are underwater, delaying their return to the surface if they detect danger. “We didn’t end up finding a relationship, but that may be because it’s a fine-scale event occurring in a matter of seconds that we weren’t able to capture—yet.”
These tactics could also inform how seals respond to other predators gaining better access as sea ice melts, including killer whales. If seals are attuned to polar bears’ footsteps on the ice, the same tactics might not work as well with killer whales. “I think potentially, killer whales could be a harder predator to avoid because one of the ways seals escape polar bears is they’re generally better swimmers. But killer whales are excellent swimmers.”
The team also notes that as the sea ice shrinks, relative bear density on the remaining ice could spike, raising short term risk for seals even before long term bear numbers continue to decline. For planners, the message is simple: build habitat models that include both sides of the equation—food and fear—so protections match how animals actually live. “This is about giving managers the most accurate picture possible,” said Dr. Florko. “When we factor in predators and prey together, we make smarter decisions for wildlife and for the people who depend on them.”
This study was conducted by researchers from UBC, York University, the Department of Oceans and Fisheries, and the Ontario Ministry of Natural Resources and Forestry.
Tags: Arctic, climate change, IOF alumni, Katie Florko, killer whales, Marie Auger-Methe, pinnipeds, polar bears, predators, ringed seals, sea ice, seals, statistical ecology