A NOAA Fisheries researcher in Seattle who’s leading an international team of scientists has compiled a model to predict growth, survival and reproductive strategies for all known fish species in the world.
“We’re using a Robin Hood approach,” said Jim Thorson, the leader of the Habitat and Ecological Process Research (HEPR) program at the Northwest Fisheries Science Center in Seattle.
“Steal from the data-rich fish, give to the data-poor,” he said in a report released March 27 by NOAA Fisheries. “Our study extends the approach to life-history theory.”
The model advances NOAA’s ability to predict impacts of climate change. Besides improving the knowledge of many species traits, it offers the capability to include hundreds of fish species simultaneously in ecosystem models.
Global results suggest that a 1-degree Celsius increase in temperature is associated with an average 3.5% increase in mortality and 3% decrease in fecundity on evolutionary time scales.
Thorson said follow-up research is planned to integrate experimental data regarding climate thresholds and species temperature preferences. The goal is to predict climate thresholds for more than the 200 species that have been measured experimentally in a lab.
“It seems intuitive that the life histories that we can currently identify can be used to improve predictions of how species will respond to climate,” he said. “However, we’re just at the beginning of that next extension.”
The model is currently being used in Alaska to improve estimates of natural mortality for rockfish. “Rockfish are small but long-lived—that’s not what we would usually expect,” Thorson said. “They are able to remain small because they have developed defenses like spines. Our model captures that aspect of their life strategy.”
The same model is also being applied globally for more data-poor species. The model has been used by the Food and Agriculture Organization of the United Nations, the International Council for the Exploration of the Sea and throughout the Pacific Ocean, NOAA officials said.
Thorson and his fellow researchers also are looking at improving spatial forecasts of species response to climate conditions occurring over a term of one to five years, a period that often directly impacts harvesters and coastal communities.
“We would love to predict ‘climate vulnerability’ for all described fishes, and we’re laying the foundation now by answering basic questions about climate vulnerabilities for well-studied species in Alaska,” he said.
According to Thorson, the model has wide relevance beyond fish, and researchers could to the same for crab, coral or octopus, as well as terrestrial ecosystems, to look at insects, mammals and birds.
“The hardest part of stock assessment is setting the biological reference point: how much can we fish a species? Knowing how many fish there are is not enough,” Thorson said. “We need to know how quickly they reproduce and how sensitive they are to change.”
“Understanding traits and life strategies gives us a reference point for sustainable catch now and in the future,” he added. “Knowing traits of the fish we manage is mandated for fisheries stock assessment improvement, but not all traits can be assessed for all species. This research fills those gaps.”
Species’ traits are shaped by their individual past environments, which are key to predicting how they will respond to future changes. Traits like body size, level of parental care and longevity reflect the adjustments species make between growth, reproduction and survival.
“All species’ traits are the result of tradeoffs among these things,” Thorson said. “That’s how we end up with a short-lived guppy that reproduces early and often, versus a shark that lives 20 years, versus a rockfish that doesn’t begin spawning for decades and lives 100 years.”
In the 1990s, researchers began categorizing fish among three dominant life-history strategies:
Opportunistic species are adapted to colonize unstable environments, mature early, have few offspring and provide little parental care.
Periodic specials exploit somewhat more stable environments, including those with seasonal changes, mature late, produce many offspring and offer little parental care.
Equilibrium species that thrive in highly stable environments with high levels of competition and predation, mature late, have few offspring and offer a high level of parental care.
NOAA officials said this is the first study that assigned all described fish to these three strategies.
The model created by Thorson’s HEPR work included 33 variables representing life cycle, reproductive, size and behavioral traits for all 34,000-plus known fish species in the world. Using relationships between measured traits known from assessed species, it predicted missing traits for other species.
They modeled effects of increased temperature on fish communities and produced the most complete “tree of life” to date that included both bony fish and sharks.
“For the first time, we can look at the tradeoffs all species make between growth and reproduction, and what that means for their survival in a changing environment,” Thorson explained.
Thorson grew up in Portland, Oregon where his grandfather, Thomas B. Thorson, was an ichthyologist, a marine biologist studying different fish species. His grandfather, who was interested originally in why sharks have such big livers, did shark tagging and life-history work on that species.
So, in some ways his grandson said, sorting out why fish are the way they are is a family business.
Thorson earned a masters’ degree in fisheries and wildlife science at Virginia Tech and a doctorate in fisheries and aquatic science from the University of Washington. He joined NOAA Fisheries in 2012 and worked as a stock assessment scientist at the Northwest Fisheries Science Center until 2018.
He’s now a statistical ecologist researching topics supporting sustainable fisheries management at Resource Ecology and Fisheries Management.
“Fisheries are endlessly interesting—where people and nature exist together. The goal is to look for win-win solutions to improve fishing opportunities while sustaining ocean resources for generations and millennia,” Thorson said.
“As scientists, we are always looking for ways we can use limited resources to gain what information we can and improve information to achieve win-wins,” Thorson remarked. “Field research, new sampling methods and whole-of-ecosystem analysis will help us find new solutions and more efficient ways to better understand ecosystem changes.”