Tuna for sale at the Tsukiji Fish Market in Tokyo. Credit: Wikimedia Commons
Appearing in everything from sushi rolls to sandwiches, tuna are among the world’s favourite fish. But are our current tuna fishing habits sustainable?
Probably not, according to a new global database of tuna catches created by researchers at the University of British Columbia and University of Western Australia.
In a study published in Fisheries Research, scientists from the Sea Around Us initiative found that global tuna catches have increased over 1,000 per cent in the past six decades, fueled by a massive expansion of industrial fisheries.
The findings indicate that these fisheries — which have been catching nearly six million tonnes of tuna annually in recent years — are operating substantially over capacity. That’s because fisheries have fully exploited or over-exploited populations of tuna and other large fish species and spread out to point where no new fishing grounds remain to be explored.
“The continuation of tuna fisheries’ catch, employment numbers and revenue figures at levels similar to the present day depends on the long-term sustainable management of the fisheries and fleets exploiting these stocks and ecosystems, and the cooperation of more than 100 countries engaged in tuna fisheries,” said lead author Angie Coulter, a researcher at the Sea Around Us initiative at the Institute for the Oceans and Fisheries at UBC.
But proper management requires accurate data, which is why Coulter and her colleagues produced the first comprehensive global data set that estimates the amount of tuna taken out of the ocean and where the fish are being caught, since 1950. The data also includes by-catch of species the fishers do not intend to catch – such as endangered sharks and other large fish – and other fish discarded overboard at sea.
The researchers created the database by assembling and standardizing all of the different public data sets created by tuna regional fisheries management organizations (RFMOs). These data sets only focus on specific areas such as the Indian Ocean or the Pacific Ocean, do not use the same reporting criteria and therefore do not provide an accurate picture of the true extent of fisheries for tuna and similar fish.
“By combining the data sets of the five existing RFMOs since 1950, we were able to create a complete picture of the evolution and current state of this fishery that mobilizes billions of dollars worldwide, feeds millions and affects areas that are shared by all countries,” said Coulter.
They found that skipjack and yellowfin are the most commonly caught species of tuna, with combined catches of four million tonnes per year in recent years. Meanwhile, catches of the sushi-favourite bluefin tuna have declined heavily since the mid-20th century, with the species now considered critically endangered.
Besides the alarmingly high amount of global catches, the researchers found that the Pacific Ocean provides 67 per cent of the world’s total tuna catches, which are mostly taken by Japanese and U.S. fleets. The Indian Ocean follows, with 12 per cent of catches by mostly Taiwanese, Spanish, Indonesian and French fleets, while the Atlantic generates an additional 12 per cent and is exploited by Spanish, French and more recently, Japanese and Korean vessels operating under Ghana’s flag.
Blue sharks comprise almost 23 per cent of the “other” fish caught during tuna fishing activities, and are also a species at risk.
“Unlike tuna, sharks take many years to mature and do not produce many offspring,” said Coulter. “This makes their populations particularly vulnerable to these fishing pressures. And the worst part is that many of these sharks are not brought to land so their meat can be used as food. They have their fins removed and sold in shark fin markets, or are simply thrown overboard as discards.”
The study estimates that 5.7 million tonnes of different shark species were discarded between 1950 and 2016 in the Pacific Ocean alone.
“It’s so important to know what’s being fished where, and in what amount in order to assess the health of fish stocks and to ensure we have fish for the future,” said Coulter. “Hopefully, the results of our study will encourage stakeholders and policymakers to increase monitoring, share information and agree upon coordinated efforts like cutbacks, to foster the sustainability of tuna stocks.”
Youth climate activists around the world are planning a Global Climate Strike during the week of Sept. 20-27 to demand action on the climate crisis. Millions of people could join the protest. Ahead of the strike date, several UBC experts who work in climate-related fields were asked for their views on climate change action.
If you were to recommend one policy action to address the climate crisis, what would it be?
Juan Jose Alava studies and conducts modelling to understand the interactions of climate change and pollutants in marine ecosystems and food webs.
“I would push for a policy action fostering and implementing the production and use of green, cleaner and more sustainable energy based on a long-term, oil-free economy to reduce our CO2 emissions and carbon footprint. These changes can proactively start by changing our food consumption preferences and transportation behaviour, from the individual level through to sustainable communities, industrial transitions and bold decisions by the government.”
Simon Donner is an interdisciplinary climate scientist who studies how climate change effects society and the environment.
“Climate change is a collective action problem that won’t be solved by any one policy. But if I can only choose one for Canada or the U.S., it would be to create proportional voting systems, such that every person in each country has an equal say in the federal leadership. Most people in North America want climate action—our governments should reflect that.”
Kai Chan is a sustainability scientist, trained in ecology, policy and ethics who strives to understand how social-ecological systems can be transformed.
“Addressing the climate crisis appropriately will require a wholesale transformation of our economy, which will take a bevy of policies carefully designed to interact synergistically. Key pieces include substantial carbon pricing (more than $100/tonne), eliminating fossil fuel subsidies, and zoning and infrastructure investments that create easy compact communities.
However, effective and efficient climate policy doesn’t necessarily sell politically, so what we need is politically enticing climate policies. I’d suggest establishing a credible national system of greenhouse gas accounting and offsets, and giving individuals and corporations tax credits for being climate-neutral. This way, substantial money is leveraged for climate action at little cost to the government, without the flavour of a ‘tax’, all while deftly encouraging changes in business and lifestyles.”
The migration of fish due to unmitigated climate change could net fisheries in the Arctic 37 times more fish than current annual catch amounts by the end of the century, a new study from the University of British Columbia has found. But, the researchers warn, any future commercial fisheries must ensure species and ecosystem sustainability and consider the food security implications for local communities.
Travis Tai
UBC researchers Travis C. Tai, a post-doctoral researcher at UBC’s Institute for the Oceans and Fisheries, and Rashid Sumaila, professor at UBC’s Institute for the Oceans and Fisheries, modeled the future of commercial fisheries in regions across Canada’s Arctic and found that the potential amount of fish that could be caught sustainably is much greater than current reported catches. These findings were based on a high climate change scenario, in which the Arctic continues to see record ice melt, and ocean warming in southern regions drives species poleward towards cooler waters.
The study, published recently in Marine Policy, also found that under a moderate climate change scenario where emissions are curbed, a moderate amount of fish could still be caught sustainably.
Currently, marine capture fisheries in Arctic Canada are small relative to other regions in the country, but small scale, community fisheries — predominantly in Inuit communities — are more widespread. The average annual catch between 2005 and 2014 was 189,000 tonnes of fish across all four Arctic regions, with the average annual value for the same period estimated at $560 million.
Arctic ecosystems may not be ecologically suitable as a refuge for sub-polar species, or resilient to increased exploitation, say the authors
Comparisons conducted in the study suggest the annual sustainable fisheries catch potential could be much greater at 4.07 ( ± 2.86) million tonnes. In a high climate change scenario, this number increases to 6.95 ( ± 5.07) million tonnes of catch in the future (2091-2100). Under a low climate change scenario, catch potential was similar to current estimates.
However, Tai, lead author of the study, warned that their estimates should be interpreted with caution.
“Climate change and more favourable environmental conditions are triggering increased exploration and development of commercial fisheries in Canada’s Arctic, but Arctic ecosystems may not be ecologically suitable as a refuge for sub-polar species, or resilient to increased exploitation,” said Tai. “What our results reinforced was the need to take proper measures to ensure the sustainability of our Arctic resources while considering the ecological, social, cultural, and economic impacts to one of the only unexploited and pristine marine regions left in the world, and the communities that live there.”
This includes assessing the impacts on marine mammals and Arctic ecosystems, subsistence fishing for Inuit communities, the dangers and environmental cost of travel, fishing seasons, and historical travel routes, among other factors.
The study highlights the effects of climate change on current and future species distribution and abundance as climate change and increasingly favourable environmental conditions trigger renewed exploration and development of commercial fisheries.
“Our goal was to evaluate the current and long-term potential of commercial Arctic fisheries in Canada with regards to its contribution to food security and the economy, even in regions that already have substantial commercial catches, such as Baffin Bay,” said Sumaila. “Because these areas are more or less undeveloped, they present a unique opportunity to extensively study and assess how best to achieve sustainable outcomes.”
The study aimed to estimate existing fisheries and, using an integrated modelling approach, build scenarios to estimate current and future fisheries potential under different climate scenarios. This allowed the study authors to use projection models to estimate changes in the distribution and abundance of commercially-valuable polar and sub-polar species. Potential fisheries catch was estimated along with the potential catch-value of commercial species across Canada’s Arctic.
“We were interested in the implications of developing large-scale commercial fisheries in Canada’s Arctic and assessing the region’s ability to support management and sustainability of marine fisheries resources into a changing future,” said Tai.
This work was supported by OceanCanada, a partnership supported by the Social Sciences and Humanity Research Council of Canada (SSHRC), as well as the Marine Environmental Observation Prediction and Response Network, Environment and Climate Change Canada, Fisheries and Oceans Canada, the Marine Affairs Program, the Nippon Foundation-UBC Nereus Program, and the Natural Sciences and Engineering Research Council of Canada.
The HCI food webs field team: (l to r) Jessica Schaub, Caterina Giner, Rosie Savage, Vera Tai, Brian Hunt, Jackie Maud, Lauren Portner, Anna McLaskey, Colleen Kellogg
The connections between the animals that form the base of marine food webs are still largely unknown. This critical knowledge gap is an area that the Hakai Coastal Initiative Marine Food Webs Working Group (FWWG) specifically aims to fill. Doing so would improve our understanding of how the plankton and microbes that ultimately supports the majority of marine life would respond to climate change. Spearheaded by Dr Brian Hunt (Director, UBC Pelagic Ecosystems Lab), Dr. Colleen Kellogg (Hakai Institute) and Dr Vera Tai (Western University) the FWWG is using a variety of cutting-edge genomic techniques to assess the community structure and interactions of marine pelagic species.
Over the summer of 2019 their team of postdoctoral fellows, students, volunteers, and a technician headed to the Hakai Institute’s field station on Quadra Island for an intense ten (10) days of sampling. The team was focused on collecting data on the day/night behaviour of bacteria, protists, zooplankton, and parasites in the Strait of Georgia. It is relatively rare to get night samples and this data will help understanding which species are in the water column at different times of the day, and what they are eating whilst they are there. To do so, the team collected samples at different depths, from surface to 200m three times per day (morning, afternoon, night) for a total of four days. The team will process the samples once they return to UBC; typically, this involves extracting and sequencing the DNA from each sample to characterize the microbial and zooplankton community. This technique (called ‘metabarcoding’) will also be used during molecular gut content analyses to identify what the zooplankton are eating.
Caterina Giner collecting DNA
To characterize the microbial components of the food web (i.e., bacteria and protists) Dr. Caterina R. Giner and Dr. Colleen Kellogg filtered several litres of seawater from every visit to the sampling site. This way they were able to collect the miniscule nano- and pico-plankton. “Bacteria and small protists are mostly lacking in morphological characteristics that allow us to identify them under the microscope. So, once in the lab, we will extract and sequence the DNA and RNA, which will tell us which microbial species are there, but also which ones are more active at the different times of the day,” said Dr. Giner.
Heading out for night sampling
The team was also interested in what these tiny organisms were doing throughout the day. Many zooplankton perform a daily migration from the depths during the day to the surface after dark. This process, called diel vertical migration (DVM), is a predator avoidance mechanism, where species hide in the depths during the day and come to the surface to feed at night when there is less chance that they might be seen by predators. Dr Jacqueline Maud (Hakai Postdoctoral Fellow, IOF), a plankton ecologist, was collecting zooplankton from varying depths during the 25 hour period to see where certain key species are and what they are eating at that depth. “Marine scientists rarely get the opportunity to sample zooplankton at night and it’s a very different landscape out there once the sun goes down and the zooplankton come to the surface” comments Jacqueline. She adds “We’re so lucky that we can use the Hakai Institute boats and equipment to collect plankton after dark, also because many jellyfish appear at the surface at night and we can find out what they’re feeding on.”
Gelatinous zooplankton are generally less well studied than other hard-bodied zooplankton. Both Dr. Maud and IOF Master’s student Jessica Schaub are hoping to change some of that. Jessica is focusing on the moon jelly Aurelia aurelia and was collecting individuals to undertake molecular gut content analysis of their stomachs.
Dr Vera Tai (Western University, Ontario) and Master’s student Rosie Savage are looking at the food web from a different perspective. Using metabarcoding they are hoping to detect zooplankton parasites from some of the dominant zooplankton species; a topic which very little is currently known about. Some parasites can be seen in and on the body of the zooplankton individuals, but these are easily missed; DNA metabarcoding can detect their occurrence.
Sorting the catch
Collectively this research will unite all the new information obtained from the different components of the food web; the scientists will be able to identify the key players but also the interactions between them. Dr Hunt commented that “this work is novel in that we are trying to pull together knowledge from every component of the plankton food web and use it to inform how the Strait of Georgia ecosystem will respond to pressure like warming and ocean acidification.” By doing so this team aims to contribute to understanding of the role of plankton in the survival of salmon and herring in BC coastal waters.
A new scientific instrument now in operation at UBC could help us further our understanding of the oceans and climate change. Called climate-controlled growth flumes, these cabinet-sized instruments look like clear, water-filled aquarium tanks connected to a control box by two large arms, and are currently used by Dr. Patrick Martone and his lab to study kelp.
“We’re really interested in kelp development – how kelp grow, and how different factors in the environment affect their growth,” said Martone, a professor in UBC’s Department of Botany and a principal investigator on a number of projects with the Hakai Coastal Initiative. His lab, the Martone Lab, studies various aspects of seaweed ecology, physiology and evolution, conducting most of their research along the B.C. coast but also in other countries, including the United States, Japan, Chile and Taiwan.
“Using these climate-controlled growth flumes allows us to answer questions about kelp that we couldn’t out in the field,” said Martone. As their name suggests, the flumes provide a controlled environment for kelp growth where scientists can experimentally manipulate flow conditions and other environmental factors, while keeping other aspects of the environment constant. Through this, scientists can determine what causes kelp to grow in certain ways, and can also create environmental conditions that mimic the projected future state of our oceans, allowing them play out “what if” scenarios for situations like climate change.
There are only six climate-controlled growth flumes in the world, all found in Martone’s lab at UBC. Developed by Martone and a local engineering firm, Coanda, the flumes were funded by two different Canadian Foundation of Innovation (CFI) grants, while their ongoing operation is funded by CFI and an NSERC Discovery Grant.
The birth of the flumes
Martone’s idea to develop the flumes came from a study he was conducting years ago in California. After transplanting seaweeds from the field into a water table in the lab, he noticed that the specimens started to grow very differently.
“I knew that the lab environment was extremely different from their ocean environment, but I couldn’t figure out which environmental factor was inducing this change in growth form,” said Martone, noting that after being transplanted into the water table, the seaweeds received less light, stayed at a constant temperature, and experienced virtually no water motion.
“This may seem trivial, but shape change in growing seaweeds confuses ecologists and taxonomists, and can also be key to the survival of seaweeds in moving water. And we know little about that process.”
Experiments conducted “in the field”, or outside of a controlled laboratory setting, are influenced by a variety of factors. For example, kelps growing naturally in the ocean are affected by fluctuating temperatures, varied light levels during different times of day, changing pH levels, water flow or speeds in different locations, animal grazing, and much more.
“That is why I was determined to design an experiment where I could manipulate one environmental factor, like light or flow, but keep all other factors constant. In particular, the ability to manipulate flow speed and direction is huge. Not many aquaria are able to provide realistic flow conditions, making these growth flumes functionally unique,” Martone said.
Footage of kelp in a climate-controlled growth flume, in real time and slow-motion. Credit: Liam Coleman / Martone Lab.
The climate-controlled growth flumes allow researchers to do just that. By programming the flume with very specific instructions, they can create their desired environmental conditions, such as having oscillating flow, or having temperature in the flume increase over the course of a week, and more. The researchers can control these different factors independently to experimentally investigate what causes seaweed to grow or respond in certain ways, something that can be difficult or impossible to accomplish in the field given scientists have little control over naturally-occurring environmental conditions.
Putting the flumes to the test: How temperature affects bull kelp morphology and survival
One of the things Martone and his lab have investigated with these flumes so far is how temperature might affect the ability of bull kelp to change their morphology, or their shape, in areas with high and low water flow. Past research has shown that kelps are very adept at changing their blade shape to help them survive under different environmental conditions, but if increased temperatures interfere with this ability, kelp may fare worse under increasingly hotter waters from climate change, if not directly then indirectly.
“We know that in current- or wave-exposed areas with high flow, bull kelp tend to grow narrow and flat blades to reduce drag, making it less likely that their blades will get torn off,” Martone explained. “In areas with slow flow, however, such as in wave-protected areas, they usually grow broader blades with more ruffles. Broad blades maximize the amount of light they get, and ruffles induce flapping to help stir up stagnant water at the blades’ surface, helping with nutrient and gas exchange.”
To first understand how bull kelps’ growth is affected by temperature, Martone, his graduate student Liam Coleman and undergraduate student Varoon Pornsinsiriruk created the first thermal performance curve for the species, a graph that maps the ideal temperature for kelp growth and also the threshold temperature at which kelp growth starts to decline. The curve demonstrated that bull kelp have a broad thermal optimum, meaning the species can resist very warm temperatures overall.
Next, Martone and his lab wanted to find out if increased temperature would affect the ability of seaweeds to adapt their shapes to environments with different water flows, since seaweeds’ ability to change their shapes is crucial to their survival. To study this, they grew bull kelp blades in flumes with different combinations of water speeds and temperatures, and observed changes in the kelp’s shape.
What the researchers found was that higher temperatures might actually interfere with a kelp’s ability to change its blade shape. When temperatures were increased, all kelp tended to grow thin and narrow, even for kelp in flumes with slower-moving water which would have benefited from growing broader blades. This has important implications for climate change and warming oceans.
“While our thermal performance curve shows bull kelp can still grow in warmer conditions, we’re finding that kelp growing in wave-sheltered areas with slower water flow may still suffer. Higher temperatures interfere with their ability to grow broad blades, therefore making it harder for them to effectively exchange gas and nutrients,” Martone explained. “However, it seems that wave-exposed kelp populations, or those in fast-moving water, will be fine even if temperatures rise, because their thin blades are already suited to their environment.”
He added that if wave-sheltered areas become even hotter than wave-exposed areas due to lack of water movement, this could exacerbate the effect.
“Despite having spent so much time thinking about the ability of kelps to change shape to resist drag, our results suggested that, as the water warms, we should pay closer attention to kelp survival in calm areas,” said Martone. “Although we don’t fully understand the mechanism of shape change, we now know that water temperature affects it.”
Future plans for the flumes
These experiments are important not only for understanding how rising ocean temperatures might affect kelp, which are crucial species that provide habitat and food in many marine environments, but they also have direct applications to the growing industry of seaweed aquaculture. Understanding ideal temperatures for kelp growth and what affects seaweed morphology is useful for determining how to farm seaweed quickly and under conditions that will create a desirable shape and texture.
Another project Martone is planning to start soon involves tracking kelp development over time, starting with spores. Through this, he can determine how much of the developmental process is fixed and, conversely, how much of it depends upon environmental factors.
“We’ve also had some interest from invertebrate scientists to grow sea stars, crabs, or snails with seaweeds in these flumes for their own research,” Martone said. “All this really speaks to the versatility and potential for these flumes to investigate questions about climate change, ecology, physiology, developmental biology, and more.”
Researchers from the Sea Around Us initiative at the University of British Columbia analyzed more than 50 studies related to the increase in vessels’ catching power.
Technological advances are allowing commercial fishing fleets to double their fishing power every 35 years and put even more pressure on dwindling fish stocks, new research has found.
Researchers from the Sea Around Us initiative at the University of British Columbia analyzed more than 50 studies related to the increase in vessels’ catching power and found that the introduction of mechanisms such as GPS, fishfinders, echo-sounders or acoustic cameras, has led to an average two per cent yearly increase in boats’ capacity to capture fish.
“This means that if a fleet has 10 boats today, one generation later, the same 10 boats have the fishing power of 20 vessels. The next generation, they have the power of 40 boats, and so on,” said Deng Palomares, the Sea Around Us project manager and lead author of the study, which was published today in Ecology and Society.
An increase in fishing power is known as ‘technological creep’ and it’s usually ignored by fisheries managers who are in charge of regulating how many days and hours and technique each vessel under their oversight is supposed to fish in a given period.
“This ‘technological creep’ is also ignored by most fisheries scientists in charge of proposing policies,” said Daniel Pauly, the Sea Around Us principal investigator. “They tend to conduct short-term studies that only take into account nominal effort, which is, for example, the number of boats that fish using longlines in one year, employing ‘x’ number of people. However, they are disregarding the effective effort those vessels are deploying thanks to the technology that allows them to either maintain their catches or catch more fish.”
In their paper, Palomares and Pauly propose a new equation that allows fisheries managers and scientists to easily estimate technological creep precisely and determine a fleet’s effective effort.
“This is important because if you don’t understand that the increase in power is happening, then you don’t understand that you can deplete a stock,” Pauly said. “We already know that marine fisheries catches have been declining by 1.2 million tonnes per year since 1996 so, by prompting boats to fish deeper and farther into the high seas, these new technologies are only helping the industry compensate for the diminishing abundance of fish populations.”
Calling him a “wonderful person, inspiring scientific leader, and incomparable mentor for many young scientists,” Carl Walters, professor emeritus in the Institute for the Oceans and Fisheries, mourned the passing of C.S. “Buzz” Holling on August 16, 2019.
Recognized as one of the world’s leading ecologists, having made major contributions to the theory of predation, the concept of ecological resilience, the concept of panarchy, and adaptive management, he received numerous awards including the Mercer and Eminent Ecologist Awards from the Ecological Society of America, the Volvo Environment Prize, and honorary doctorates from Guelph, Simon Fraser, and UBC. He was a Fellow of the Royal Society of Canada and had received the Order of Canada.
Holling was born in 1930 and obtained his Ph.D. from the University of British Columbia in 1957. He worked as a research scientist in the Canadian Forest Service before returning to UBC, this time as a professor. He was the first director of the Institute of Animal Resource Ecology (now Institute for the Oceans and Fisheries), which is where, as a junior faculty member, Dr. Walters was his colleague. Eric Charnov, Distinguished Professor of Ecology & Evolutionary Biology at the University of Utah, was one of Holling’s postdoctoral fellows, and concurs with Walters’ assessment. “He was wonderfully supportive and fun to talk with, particularly when we disagreed, which was often,” said Dr. Charnov. “Buzz trained many distinguished scholars, which reflects very much on his mentorship, as noted by Carl. I am proud to have been among them.”
He left UBC in the late 1970s to direct the International Institute for Applied Systems Analysis (Vienna, Austria), returned briefly in the early 1980s, before moving to the University of Florida. After retirement he lived for several years in Cedar Key, Florida, then returned to Nanaimo, B.C. for the last years of his life.
Dr. Rashid Sumaila is one of seven UBC faculty members who have been named as Fellows of the Royal Society of Canada (RSC).
The fellowship of the RSC comprises over 2000 Canadian scholars, artists, and scientists, peer-elected as the best in their field. These are distinguished men and women from all branches of learning who have made remarkable contributions in the arts, the humanities and the sciences, as well as in Canadian public life.
Prof. Sumaila is one of the world’s most innovative researchers on the future of the oceans, integrating the social, economic and fisheries sciences to build novel pathways towards sustainable fisheries. His work has challenged today’s approaches to marine governance, generating exciting new ways of thinking about our relationship to the marine biosphere, such as protecting the high seas as a “fish bank” for the world and using “intergeneration discount rates” for natural resource projects.
“I feel massively honoured to be inducted into the Fellowship of the Royal Society of Canada,” said Prof. Sumaila. “This is the highest recognition that fellow Canadian scholars can bestow on one of their own! It reminds me of a saying that I’ve taken to heart; “Anyone who puts in his or her best will never regret it.” Young scholars, remember this and just keep pushing!”
Three new viruses — including one from a group of viruses never before shown to infect fish — have been discovered in endangered Chinook and sockeye salmon populations.
Chinook salmon found dead at British Columbia spawning grounds (Credit: Kristi Miller-Saunders, Fisheries and Oceans Canada).
While the impact of the viruses on salmon health isn’t yet known, all three are related to viruses that cause serious disease in other species.
“We were surprised to find viruses which had never before been shown to infect fish,” said Gideon Mordecai, researcher at UBC’s department of earth, ocean and atmospheric sciences. “Although there’s no risk to humans, one of the viruses is evolutionarily related to respiratory coronaviruses, and is localized to the gills. That suggests it has a similar infection strategy to its distant relatives that infect mammals.”
UBC and Fisheries and Oceans Canada researchers used DNA sequencing followed by tests specific to each virus to screen more than 6,000 salmon from along the B.C. coast, including wild, hatchery and aquaculture fish.
“We found the new viruses widely distributed in dead and dying farmed salmon and in wild salmon,” said UBC virologist Curtis Suttle. “It emphasizes the potential role that viral disease may play in the population dynamics of wild fish stocks, and the threat that these viruses may pose to aquaculture.”
Pacific Salmon Foundation researchers sample overwintering Chinook to be screened for infectious agents, Quatsino Sound, BC, March 2019 (Credit: Amy Romer)
One new virus, detected more commonly in salmon hatcheries, infected more than 15 per cent of all hatchery Chinook tested.
Another new virus was detected in 20 per cent of Chinook from fish farms —but was only found in adult or sub-adult salmon. In general, the new viruses were more commonly found in cultured fish populations than in wild.
“It’s essential that we determine whether these viruses are important factors in the decline of Chinook and sockeye salmon stocks,” said Suttle. “The research highlights the need for robust surveillance to improve our understanding of how viruses might impact the health of wild Pacific salmon populations.”
Over the past 30 years, steady declines in Chinook and sockeye salmon populations have been of great concern to Indigenous peoples, commercial and recreational fishers, and the general public. While much of the focus has been on the impact of piscine orthoreovirus (PRV), the new findings highlight how little is known about other viruses endemic to salmon populations.
“Being able to screen so many fish for these viruses was an exciting breakthrough, and meant we were able to identify hotspots of infection,” adds Mordecai.
Pacific Salmon Foundation researcher dissects tissue samples from overwintering Chinook to detect for the presence of infectious agents, Quatsino Sound, BC, March 2019 (Credit: Amy Romer)
“One of the viruses was relatively common in juvenile migratory salmon as they enter the ocean—a period thought to be critical to their survival into adulthood.”
The work was funded as part of the Strategic Salmon Health Initiative, a partnership of GenomeBC, Fisheries and Oceans Canada, and the Pacific Salmon Foundation.
Postdoctoral researcher, Dr. Jessica Garzke, conducting the experiment
Climate change and biodiversity change are two major ecological crises of our time, but new research finds that whether ecosystems can adapt to such pressures may depend on the presence of predators. In an experiment, University of British Columbia researchers found that when predators were not present in the ecosystem, the overall biomass and abundance of algae declined greatly with increasing temperature, leaving less energy available for all organisms.
Dr. Jessica Garzke, the study’s lead author and postdoctoral fellow in the Institute for the Oceans and Fisheries, and Dr. Mary O’Connor, senior author on the paper and professor in UBC’s Department of Zoology, explain why this might have happened.
What were you investigating?
Dr. Jessica Garzke
JG: We wanted to find out whether the presence of predators, including their relationships with other organisms like prey, leads to different overall production or energy levels in an ecosystem. As our climate changes, it is important to understand how key roles like predators might buffer against changes at an ecosystem level.
How did you set up this experiment?
JG: To test our hypothesis, we created a series of independent freshwater tank ecosystems, and filled each tank in one of three ways to reflect different trophic structures: with algae only, with algae and grazers, or with algae, grazers and predators. We created multiple tanks for each trophic structure and set each to a different temperature, ranging from 19 to 30°C, to see how increasing temperatures might affect ecosystems when different species are present. We then tracked changes in these tanks over 9 weeks.
What were your main findings?
MO: We found that warming had a bigger impact on the ecosystem when predators were not present. In our case, these predators were aquatic insects called notonectids, which prey on zooplankton.
In the tanks where there were notonectids, we found that the algae biomass was relatively high, meaning there was a lot of energy still available for organisms in that ecosystem even when temperatures increased. However, when notonectids were not present the abundance of algae declined greatly with higher temperature, leaving less food available overall. This highlights the key role of predators in ecosystems, and how they may be crucial to helping ecosystems adapt to warming.
Anything surprising about what you found?
JG: Yes! While we found that, at high temperatures, there was less food available for zooplankton when no notonectids were present, we also found that the increased temperatures did not lead to species loss or an entire collapse of the community in the zooplankton. The diversity of the grazer communities appeared resilient to warming, even though the ecosystem function (oxygen flux) and ecosystem structure (algal abundance) were quite sensitive to warming. Even with temperature increases in our tanks, there was enough time for the algae species in the experiment to compensate because algae have a lifecycle and reproduce fast in the 9-weeks of the experiments and even faster at higher temperatures as they grow waster with warming.
Why are your findings important?
Dr. Mary O’Connor
MO: This experiment demonstrated that biodiversity change, in the form of the loss of predators, can exacerbate the effects of warming on ecosystem function. We know that warmer temperatures affect ecosystems, from cells to population growth rates to ecosystem functions. At higher temperatures, ecosystems are more productive and take up carbon faster, and at the same time animals require more food. This occurs at the same time as climate change is occurring, rendering top predators highly vulnerable.
It is important that research looks into how these climate change and biodiversity change might interact with one another, and how the impacts of warming could be dependent on trophic structures within ecosystems.
