Seasonality and Life History Complexity Determine Vulnerability of Dungeness Crab to Multiple Climate Stressors

Abstract

Scaling climate change impacts from individual responses to population‐level vulnerability is a pressing challenge for scientists and society. We assessed vulnerability of the most valuable fished species in the Northwest U.S.—Dungeness crab—to climate stressors using a novel combination of ocean, population, and larval transport models with stage‐specific consequences of ocean acidification, hypoxia, and warming. Integration across pelagic and benthic life stages revealed increased population‐level vulnerability to each stressor by 2100 under RCP 8.5. Under future conditions, chronic vulnerability to low pH emerged year‐round for all life stages, whereas vulnerability to low oxygen continued to be acute, developing seasonally and impacting adults, which are critical to population growth. Our results demonstrate how ontogenetic habitat shifts and seasonal ocean conditions interactively impact population‐level vulnerability. Because most valuable U.S. fisheries rely on species with complex life cycles in seasonal seas, chronic and acute perspectives are necessary to assess population‐level vulnerability to climate change.

Predation Scars Reveal Declines in Crab Populations Since the Pleistocene

“…For example, ocean acidification affects crab larval development along the west coast of North America (Hodgson et al, 2018;Bednaršek et al, 2020). All life stages of Dungeness crab are also predicted to be vulnerable to year-round ocean conditions (low pH, low oxygen, and increased temperatures) by the end of the century (Berger et al, 2021). Mollusks, including T. funebralis, are also expected to experience direct consequences of ocean acidification, including impaired behavior, and reduced shell growth and strength (Jellison et al, 2016;Barclay et al, 2019Barclay et al, , 2020a.…”

“…Past studies show that Dungeness crab populations are quick to recover after spatial closures (Taggart et al, 2004;Frid et al, 2016). However, if the cause of declines in crab populations is also related to ecosystem changes and degradation on southern California's coast due to anthropogenic impacts, such as changes to macroalgal and seagrass communities (Waycott et al, 2009;Whitaker et al, 2010;Beas-Luna et al, 2020) that are often nurseries for young crabs (Robles et al, 1989;Beck et al, 2003;Holsman et al, 2006;Behrens Yamada and Groth, 2016), or to seawater conditions (Bednaršek et al, 2020;Berger et al, 2021), changes to crab fishery management policies will be insufficient to sustain these resources long-term.…”

“…More broadly, there are several other areas for improvement and continued investigation. First, addressing the ever-increasing urgency of climate change and anthropogenic impacts on coastal ecosystems and resources (Beas-Luna et al, 2020;Bednaršek et al, 2020;Berger et al, 2021) is paramount to ensuring longterm sustainability of far more than just crab fisheries. For example, as macroalgal and seagrass communities are important habitat for young crabs (Robles et al, 1989;Beck et al, 2003;Holsman et al, 2006;Behrens Yamada and Groth, 2016), any restoration of these communities will also greatly benefit crabs (Anderson, 1989).…”

“…For example, as macroalgal and seagrass communities are important habitat for young crabs (Robles et al, 1989;Beck et al, 2003;Holsman et al, 2006;Behrens Yamada and Groth, 2016), any restoration of these communities will also greatly benefit crabs (Anderson, 1989). Addressing anthropogenic carbon dioxide emissions is also key to addressing future ocean conditions, including warming, hypoxia, and ocean acidification that will impact crabs (Bednaršek et al, 2020;Berger et al, 2021). Second, conservation paleobiology and historical ecology offer unique perspectives, tools, and datasets that provide much needed and often missing context to ensure the sustainability and protection of ecosystems and their services (Hadlock Seeley, 1986;Erlandson and Rick, 2010;Dietl and Flessa, 2011;Mcclenachan et al, 2012;Rick and Lockwood, 2013;Dietl et al, 2015;Kidwell, 2015;Barnosky et al, 2017;Fordham et al, 2020).…”

Evaluating environmental controls on the exoskeleton density of larval Dungeness crab via micro computed tomography

“…Their habitat range spans cool oceans from Alaska to southern California (Rasmuson, 2013), which are vulnerable to anthropogenic ocean acidification (OA) due to naturally low seawater buffering capacity in portions of the region (Feely et al, 1988;Feely et al, 2016;Chavez et al, 2017). While the Dungeness crab fishery may currently be sustainable (Richerson et al, 2020), model projections suggest accelerating OA (Chan et al, 2017;Doney et al, 2020) will lead to future declines and considerable socioeconomic impacts, especially in Oregon and Washington (Marshall et al, 2017;Hodgson et al, 2018;Magel et al, 2020;Berger et al, 2021). However, these model projections are based on relatively limited physiological data with only modest agreement among studies (Busch and McElhany, 2016), indicating that additional work is necessary to robustly characterize the response of Dungeness crabs to OA and other stressors associated with anthropogenic climate change.…”