How ocean acidification and warming could reshape a vital industry

by Heather Nibert, UW School of Aquatic & Fishery Sciences

When the forecast looks cloudy

In the icy waters of Alaska, red king crab and southern Tanner crab scuttle through an uncertain future. The ocean around them is warming and turning more acidic, making it harder for these crabs to survive and grow. Every shift in their world sends ripples through the ecosystem and the fishing communities that depend on them.

Predicting how these crab populations will change in a warming and acidifying ocean is no simple task. Scientists must estimate how many crabs survive each year and how environmental shifts will affect their growth, but those predictions are never entirely certain. Consider the weather: if the forecast says there is an 80 percent chance of rain, most people grab an umbrella. But if that chance drops to 20 percent, many take the risk of leaving it behind. That same logic guides fisheries scientists when they provide information on the long-term prospects for how much crab can be safely caught each year. When uncertainty about crab survival and growth rises, scientists must weigh how confident they are in their forecasts before this information can be used to advise on fishing limits that affect both the ocean and coastal communities.

Forecasting crab populations is not just about knowing what might happen, it is about understanding how sure we can be. For managers, the difference between 80 percent certainty and 20 percent can mean the difference between stable livelihoods and ecosystem stress, between a thriving community and one left in the rain.

Behind the screens: What modeling really looks like

Understanding how scientists identify and measure uncertainty requires looking behind the screens where these forecasts are built. At first glance, modeling how climate affects fisheries might sound like solitary, computer-heavy work. And it is, but it is also profoundly collaborative. In a study published in September 2025, researchers at the University of Washington and NOAA Fisheries worked together across disciplines using advanced numerical models to simulate how climate change will affect the two species of crab in the Bering Sea ecosystem.

“This research is part of the Alaskan Climate Integrated Modeling (ACLIM) project, a long-term effort that brings together oceanographers, marine ecosystem modelers, and fisheries scientists to understand how environmental change will shape Alaska’s marine resources, from fish to crab,” said Kirstin Holsman, research fishery biologist at NOAA’s Alaska Fisheries Science Center. “ACLIM builds on projections from high-resolution regionally downscaled global Earth System Models, using them as the foundation for detailed regional simulations of the Bering Sea.”

Earth System Models, developed by modeling centers around the world, simulate how greenhouse gases and aerosols interact with the ocean and atmosphere through interconnected physical and biogeochemical processes. These models simulate how ocean conditions may change over the next century, including processes such as ocean acidification, which is a key focus of the NOAA Ocean Acidification Program.

“Global Earth System Models provide a big-picture forecast,” said Wei Cheng, research oceanographer at the University of Washington, “but they are too coarse to capture the fine details that matter for Alaskan crab. So, we have to dig a little deeper.”

The team “downscales” the global Earth System Model projections to the regional level using a fineresolution ocean hydrodynamical model. This turns a blurry global picture into a sharper view that reveals key regional features, such as the Cold Pool, a large mass of cold water that forms on the bottom of the Eastern Bering Sea shelf each summer. Just as the Cold Pool affects distribution of commercially important fish species, ocean temperature change and acidification determine where crabs live and how they grow.

The refined regional ocean conditions are then provided to marine ecosystem modelers and fisheries biologists to develop bio-economic models. These models lay the groundwork for the next step: connecting environmental change to the biology of crab and, ultimately, to the economics of the fishery.

Linking environment, biology, and economics

To explore how environmental changes impact living resources, researchers use bio-economic models that link ecosystem dynamics to economic outcomes. “Bio-economic models link the effects of ocean acidification, through population dynamics, to impacts on fisheries,” said Michael Dalton, economist at NOAA’s Alaska Fisheries Science Center. “It’s a multilevel model that takes you from egg production all the way to economic output.”

The bio-economic model used by the University of Washington and NOAA scientists is built using data from laboratory experiments on the effects of changing acidity on larval and juvenile crab, and from research surveys in the Bering Sea, as well as from data on costs and prices from fishers.

Using this information, the bio-economic model determines the impacts of harvest rates on crab populations, which then allows the economic model to calculate optimal fishing levels that maximize profits while sustaining populations.

The model produces output data that can be visualized as graphs, which show how removing individual sources of uncertainty reduces the spread of the projected survival trajectories. For example, omitting uncertainty related to ocean acidity effects on juvenile or larval stages narrows the range of outcomes, revealing that these effects contribute most to overall uncertainty. These visualizations help clarify where uncertainty is concentrated for each species and indicate which data or experiments would most improve future model performance and the reliability of management advice.

The importance of uncertainty

Uncertainty in science is often seen as a problem, but here it serves as a guide. If we know where the largest uncertainties lie, we can target research efforts to reduce them and improve management decisions.

“A decade ago, we had only used one Earth System Model, so this uncertainty could not be accounted for,” said André Punt, lead study author and population ecologist at the University of Washington. “But now, as we develop end-to-end modeling frameworks, we are finding that not only are the bio-economic models themselves uncertain, but the predicted values and expected trends of climate variables also vary.”

Every step in this process brings a different kind of uncertainty, such as:

• Scenario uncertainty: We do not know what choices people will make about burning fossil fuels in the future.
• Structural uncertainty: Each model is built slightly differently and makes different assumptions about how the ocean, crab stocks, and fisheries behave.
• Intrinsic uncertainty: Nature itself is chaotic. Tiny changes can grow into major differences, much like the “butterfly effect” in weather forecasting.

These uncertainties do not make prediction impossible, but they do make humility essential. “We are always balancing what we know, what we can estimate, and what remains unknowable,” said Albert Hermann, CICOES research scientist.

The largest uncertainties arise from differences among the Earth System Models and emissions scenarios. Additional uncertainty stems from incomplete understanding of how ocean acidity and temperature affect early-life survival and growth. Economic factors, including how fishing costs and market prices respond to changes in catch, also contribute to overall uncertainty. By clarifying the gaps in current knowledge, scientists can focus new studies on the questions that most improve crab forecasts.

A path forward for research and management

Future research that explores how varying levels of ocean acidity and temperature affect crab biology will be most beneficial for increasing our understanding of the long-term effects of climate on crab populations. For example, expanding the range of acidity tested for red king crab larvae and increasing sample sizes for southern Tanner crab juveniles will help reduce uncertainty.

The study also highlights the need to consider life stage-specific impacts, such as juvenile growth for red king crab and larval survival for southern Tanner crab. These insights will help scientists and managers plan future ocean acidification experiments and decide where to spend limited research funding most effectively.

Why this matters

These scientific insights matter far beyond the lab. For many Alaskan coastal towns, crab fishing is more than an industry; it is the backbone of local economies and family livelihoods. Reducing uncertainty in crab forecasts helps these communities plan for the future, adapt to changing conditions, and sustain their way of life in a changing ocean.

As temperature change and ocean acidification reshape the Bering Sea, research that quantifies uncertainty and integrates knowledge across disciplines gives managers stronger tools to set sustainable harvest limits, protecting both crab populations and the communities that depend on them.

By linking environmental, biological, and economic uncertainty to real-world management decisions, this study provides a roadmap for effective management strategies and more resilient fisheries. Prioritizing the experiments and data that most improve predictions helps managers make confident, cost-effective, and climate-informed choices, whether that means taking the “umbrella” or leaving it behind.