Forecasting the range edge threshold: A case study of blue crab (Callinectes sapidus) expansion into the Gulf of Maine

University of New Hampshire
Ashburn, Virginia
BiologyGrant: Living Thresholds - Oceans
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About This Project

Blue crabs arrived into the Gulf of Maine (GoM) during a decade of rapid warming. In the GoM, blue crabs may disrupt ecosystems by preying on shellfish or outcompeting native crabs - but are they here to stay? We use novel statistics to forecast blue crab presence in the GoM. We hypothesize that forecasts which explicitly account for crab physiology will better predict crabs’ range boundary than traditional models of environmental conditions.

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What is the context of this research?

Forecasts of species range thresholds face challenges. As species encounter unfamiliar environments at the range edge, they may experience die-offs, exhibit physiologically plastic tolerance, or a mix of both, leading to intermittant periods of presence and absence.

Species Distribution Models (SDMs) are the most common tool for range forecasting. SDMs have trouble forecasting pulses in the range threshold because they don’t account for the biotic processes, e.g. physiological plasticity, thermal tolerance, or local adaptation. However, a growing body of literature suggests techniques for integrating biotic processes into SDMs: hierarchical models that make predictions for biogeographically distant groups may account for local adaptation, while flexible Bayesian models may be able to incorporate data on species physiology from previous lab experiments.

What is the significance of this project?

Blue crabs (Callinectes sapidus) are an ideal study species. In recent years, blue crabs expanded from their historic range and entered the Gulf of Maine (GoM). Observations of blue crabs in the GoM declined after two cold years. Likely, blue crabs experienced die-offs because winter temperatures exceeded their thermal tolerances. SDMs haven’t forecasted this pulse because they don’t account for biotic processes and can’t predict die-offs from observational data because these events are unprecedented.

At the leading and trailing edges of their distributions, range-shifting species require intensive management akin to non-native species and endangered species, respectively. For example, blue crabs may cause a variety of impacts if they expand into the GoM, from competing with invasive species to preying on shellfish reefs. Our blue crab range threshold forecasts justify scientific exploration of blue crabs’ impacts and give management organizations time to prepare.

What are the goals of the project?

We will build and test unique SDMs that predict blue crabs’ range threshold. We will train models in a Bayesian framework on global blue crab occurrence data and use MOM6 regional downscaled hind- and forecasts for environmental covariates. The null model will assume blue crabs have no local adaptation to environment. One alternative model will assume heterogeneity in response according to biogeographic region (accounting for local adaptation), and another alternative will use Bayesian priors to incorporate existing data on blue crab physiology (e.g. thermal tolerance, plasticity). Models will be validated with fisheries independent survey and crowdsourcing data.

We will publish forecasts of blue crab presence in the GoM on an open-source website and publicize the website at the Maine Fishermen’s Forum and the Regional Association for Research on the Gulf of Maine conferences. We will publish innovations in SDM forecasts in a peer-reviewed journal.

Budget

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The budget includes part-time summer 2027 salary for the PI at the UNH’s Level I rate. Summer funding will enable the PI to prioritize the project and produce a manuscript for publication.

The modeling team (PI Kaila Frazer, Savannah Schilling, and Andrew Villeneuve) will solicit feedback on Species Distribution Models at the 2027 Ecological Forecasting Initiative (EFI) Conference. The PI presented a preliminary blue crab model at the 2026 EFI conference and received feedback which inspired her to explore methods proposed here. Funds will support registration and travel to EFI 2027.

The modeling team will also present preliminary forecasts at the 2027 Maine Fishermen’s Forum, a free conference for exchange of scientific and industry knowledge in Gulf of Maine fisheries. Funds will support ground transit to the Fishermen’s Forum for the PI and modeling team.

Funds will support one year of Dropbox Plus subscription (PI) to store large environmental data files.

Endorsed by

This project will be an important advancement for modeling blue crab by including realistic biological mechanisms. Kaila is the ideal person to lead this work.
I am very excited about this project, especially since a lot of my work as a fisheries specialist looks at the effects of climate on current commercial fisheries and the opportunities and challenges that they may face. Range expansion of an already established and lucrative commercial species such as the blue crab could provide opportunities for fishing communities. Being able to forecast this expansion can give us time to prepare and understand the possible impacts.

Project Timeline

Month 1: Gather biotic data on blue crab thermal tolerance and plasticity from literature.

Month 2: Build preliminary Species Distribution Models.

Months 3-4: Present preliminary forecasts at Maine Fishermen’s Forum. Prepare presentation for EFI conference.

Months 5-6: Adjust Species Distribution Models according to feedback from EFI conference. Finalize models.

Months 7-8: Build website displaying forecasts.

Months 9-12: Submit manuscript to PLOS Climate.

Nov 13, 2026

Project Launched

Mar 06, 2027

Travel to Maine Fishermen's Forum

Mar 24, 2027

Travel to Ecological Forecasting Initiative Conference

Oct 01, 2027

Submit manuscript to PLOS Climate

Meet the Team

Kaila Frazer
Kaila Frazer
Graduate Student

Affiliates

University of New Hampshire, Smithsonian Environmental Research Center
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Jennifer Dijkstra
Jennifer Dijkstra
Research Associate Professor

Affiliates

University of New Hampshire
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Andrew Villeneuve
Andrew Villeneuve
Postdoctoral researcher

Affiliates

Friday Harbor Labs, University of Washington
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Easton White
Easton White
Associate Professor

Affiliates

University of New Hampshire
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Savannah Schilling
Savannah Schilling
Master's Student

Affiliates

University of New Hampshire
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Gabriela Bradt
Gabriela Bradt
NH Sea Grant & UNH Extension

Affiliates

University of New Hampshire, New Hampshire Sea Grant
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Kaila Frazer (PI, UNH PhD student) studies SDMs. Dr. Villeneuve (Postdoc. Fellow, University of Washington) studies invertebrate thermal tolerance. Savannah Schilling (MS student, UNH) with software engineering experience. Dr. White (Associate Prof., UNH) with expertise in quantitative ecology. Dr. Ogburn (Senior Scientist, Smithsonian Environmental Research Center) brings expertise in blue crab ecology. Dr. Dijkstra (Research Associate Prof., UNH) has coastal mapping expertise.

Kaila Frazer

Kaila Frazer is an applied quantitative ecologist pursuing her PhD in the Quantitative Marine Ecology Lab at the University of New Hampshire. Kaila uses data from both laboratory and field experiments to quantify species responses to shifts in temperature occurring from daily to decadal timescales. Her work builds on traditional statistical modeling techniques (e.g. Species Distribution Modeling) to account for previously overlooked sources of variability in species presence and mortality. In her PhD, Kaila uses marine invertebrates as case studies for novel modeling techniques.

Kaila holds a BA in Environmental Science & Policy from Smith College. Previously, she worked on forecasts of extreme temperature event impacts on highly mobile marine species. She has also published on neotropical palm physiology and contributed to applied quantitative projects in high-severity burn zones.

During her PhD, Kaila has been awarded a Smithsonian Graduate Fellowship and a National Science Foundation Graduate Research Fellowship. She is a recipient of the William R Spaulding Endowment Award and a School of Marine Science and Ocean Engineering Graduate Student Fellowship. Kaila is co-chair of the Ecological Forecasting Initiative (EFI) early career working group and a member of both EFI’s marine working group and EFI’s actionable science working group.

Jennifer Dijkstra

Dr. Jenn Dijkstra is a Research Associate Professor the Center for Coastal and Ocean Mapping. She is currently the chair of the Diving Control Board and the Reseaerch Faculty Council.

I am a marine ecologist in which my group detects change in benthic systems, particularly foundation species. Within this context, we use a variety of optical (e.g., photogrammetry), remote sensing (e.g., satellite) and acoustic tools (e.g., bathymetry), and often develop methods and models for characterizing and predicting change in benthic systems. We study mutliple ecosystems that span the deep sea to kelp forests and coastal coral reefs. However, our main focus is on nearshore communities where our research questions mainly center around the detection and mapping of change in communities, causes and consequences of those changes, habitat complexity, and species distribution.

Dr. Dijkstra received a B.A. from the University of New Brunswick (Canada), a M.Sc. in Marine Biology from the University of Bremen (Germany), and a Ph.D. in Zoology from the University of New Hampshire.

Andrew Villeneuve

Dr. Andrew Villeneuve is a marine biologist based at Friday Harbor Labs (University of Washington, USA). He is interested in how marine organisms are responding to heatwave events through the lens of physiology. He uses experimental and modeling tools to build predictive models of ecophysiological stress in marine invertebrates, with the goal of applying these models for applied ecological and fisheries management needs.

Andrew earned his PhD from the University of New Hampshire, where his research focused on building heat stress models for oysters and gorgonians. Previously, he studied local adaptation of a widely distributed marine snail to understand the role of evolution in driving population-level responses to climate change. He was also a 2021 Knauss Marine Policy Fellow with NOAA Fisheries.

Andrew is a co-team lead for the Thermo ToleRate working group through the Environmental Data Science Innovation & Impact Lab (ESIIL), which seeks to understand the diversity of organisms' heat stress adaptations and test the ability for current heat stress models to predict population crashes in response to extreme heat events. He is an active member of the Ecological Forecasting Initiative, in which he served as a co-chair for the early career working group from 2024-2026.

Easton White

I am a quantitative marine ecologist who uses mathematical and statistical tools, coupled with experiments and field observations, to answer questions in ecology, conservation science, sustainability, and ecosystem management. Most of my work is focused on marine systems, especially fisheries and spatial planning. I am an Associate Professor in the Department of Biological Sciences at the University of New Hampshire. Prior to joining UNH, I was a research associate at the University of Vermont with the QuEST program, a NSF-funded PhD traineeship focused on quantitative skills, interdisciplinary work, as well as diversity and inclusion.

I currently conduct research on assessing the effectiveness of protected area networks, improving species monitoring programs, and modeling socio-ecological systems in the context of fisheries. My work centers on how environmental variability, in particular rare events (e.g., hurricanes, COVID-19 pandemic), affects ecosystems and those that depend on them. My current work is funded through a NSF grant focused on interdisciplinary approaches to study coupled natural-human systems with Madagascar fisheries as a case study.

Savannah Schilling

Savannah Schilling is a master’s student working in the Quantitative Marine Ecology Lab at the University of New Hampshire. Her research focuses on understanding how anthropogenic and natural environmental factors shape aquatic ecosystems, as well as how human industries can better coexist with the natural world. She is particularly interested in collective behavior and the spatiotemporal dynamics of ecosystems, with an emphasis on applying quantitative approaches to improve ecosystem monitoring and management. Her current work uses biosensors to measure collective gaping patterns in Eastern oysters in Great Bay.

Savannah earned her BS in Electrical Engineering from the University of Colorado, where she also conducted research on nestmate recognition in ants, biocontrol of invasive spotted knapweed in the Boulder Valley, and mechanisms of language learning in children using behavioral studies and predictive neural network models. She is passionate about combining quantitative analysis, computational modeling, and empirical data to investigate natural phenomena. Before transitioning to ecology, Savannah spent over a decade in the software industry, most recently working as a software engineer at Google, where she supported clean energy grid optimization, and as a consultant at Brocade Studio, developing operational models for community tree-planting organizations. She now brings this technical and interdisciplinary background to the study of ecological processes.

Gabriela Bradt

Gabriela is a Fisheries Extension Specialist for New Hampshire Sea Grant and the University of New Hampshire Cooperative Extension. Her programming is mainly focused around seafood marketing, market creation and consumer education and awareness about New Hampshire’s fisheries and local seafood accessibility. She has worked extensively with NH fishermen, chefs and other stakeholders in creating markets for aquaculture products including seaweed, oysters and mussels. She works closely with her Aquaculture Specialist in providing extension and scientific support to stakeholders and exploring possible avenues for expanding aquaculture and other fisheries possibilities in NH. She organizes and leads culinary and foraging workshops, fishing gear workshops and helps to guide and facilitate industry meetings. She also conducts research on invasive green crabs as a potential fishery and seafood product, soft-shell crab production and leads citizen science programs looking at green crab population and distribution in coastal NH as well as long term monitoring of microplastics and marine debris.

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