Responses of fisheries ecosystems to marine heatwaves and other extreme events

Abstract

Marine ecosystems and their living marine resources (LMRs) continue to respond to the effects of global change, with environmental factors impacting marine fisheries biomass, distribution, harvest, and associated economic performance. Extreme events such as high-category hurricanes, harmful algal blooms, marine heatwaves, and large-scale hypoxia affect major regions and subregions of United States waters, with their frequency expected to increase over the next decades. The impacts of extreme events on fisheries biomass, harvest, and economic performance have not been examined as closely as a system (i.e., cumulatively), or in terms of their differential effects on particular functional groups of a given system. Among several U.S. subregions, we examined responses of fisheries biomass, landings, and revenue for particular functional groups to large-scale environmental perturbations (i.e., marine heatwaves, Hurricane Katrina, Deepwater Horizon oil spill). Distinct negative short-term consequences to annual fisheries biomass, landings, and revenue were observed in all regions, including at the system-level scale for several ecosystems which have higher proportions of pelagic species composition and variable shellfish-based revenue. In addition, shifts in species composition often were associated with environmental perturbations. Recovery to pre-perturbation levels (both in the immediate years following the event and over the post-event period of study) and resilience at the system level was observed in several cases, although post-event declines in biomass and landings occurred in the California ecosystem. Certain extreme events are expected to become more common in marine environments, with resulting perturbations throughout multiple components of U.S. socioecological systems. The recognition and understanding of the consequences of extreme events throughout marine ecosystems is necessary for effective, holistic, and sustainable management practices.

Fig 1. Total regional biomass and landings for fisheries ecosystems over time.

For ecoregions investigated in this study (i.e., eastern Bering Sea, Gulf of Alaska, northern California, Pacific Northwest, Gulf of Maine, northern Gulf of Mexico), time series for total fisheries biomass and landings (1950–2020) are depicted. Additionally, for each region, biomass and landings trends for ten years pre-event (blue), during a marine heatwave or following an initial extreme event (pink), and post-heatwave or extreme event period (yellow) are shown. (A) For eastern Bering Sea, (B) Gulf of Alaska, (C) northern California, and (D) Pacific Northwest regions, these trends are shown ten years (2004–2013) prior to the Pacific marine heatwave (“Blob”), over the duration of the heatwave (2014–2015), and during years post-heatwave (2016–2020). (E) For the Gulf of Maine, they are shown ten years (1999–2008) prior to the onset of an accelerated warming period for the Gulf of Maine, during the accelerated warming period and prior to a subsequent marine heatwave and noted spike in temperatures (2009–2011), and for years following the 2012 heatwave and during the temperature spike (2013–2020). (F) For the northern Gulf of Mexico, trends are shown ten years (1995–2004) prior to Hurricane Katrina, in years post-hurricane and prior to the Deepwater Horizon (DWH) oil spill (2006–2009), and for years following the DWH event (2011–2020).

Fig 2. Total regional revenue for examined fisheries ecosystems over time.

For ecoregions (i.e., eastern Bering Sea, Gulf of Alaska, northern California, Pacific Northwest, Gulf of Maine, northern Gulf of Mexico), time series for total fisheries revenue (1950–2020) are shown. Additionally, for each region, biomass and landings trends for ten years pre-event (blue), during a marine heatwave or following an initial extreme event (pink), and post-heatwave or extreme event period (yellow) are depicted. (A) For eastern Bering Sea, (B) Gulf of Alaska, (C) northern California, and (D) Pacific Northwest regions, trends in revenue are shown ten years (2004–2013) prior to the Pacific marine heatwave (“Blob”), over the duration of the heatwave (2014–2015), and during years post-heatwave (2016–2020). (E) For the Gulf of Maine, they are shown ten years (1999–2008) prior to the onset of an accelerated warming period for the Gulf of Maine, during the accelerated warming period and prior to a subsequent marine heatwave and noted spike in temperatures (2009–2011), and for years following the 2012 heatwave and during the temperature spike (2013–2020). (F) For the northern Gulf of Mexico, revenue trends are shown ten years (1995–2004) prior to Hurricane Katrina, in years post-hurricane and prior to the Deepwater Horizon (DWH) oil spill (2006–2009), and for years following the DWH event (2011–2020).

Fig 3. Pelagic to demersal ratios and percent contribution of shellfish (% shellfish) per fisheries ecosystem over time.

For each fisheries ecosystem (i.e., eastern Bering Sea–EBS; Gulf of Alaska–GAK; Northern California–Cal; Pacific Northwest–PNW; Gulf of Maine–GMaine; Northern Gulf of Mexico–GMEX), pelagic to demersal ratios for (top panel) and percent contribution of total shellfish (i.e., bivalves and crustaceans; bottom panels) to total biomass, landings, and revenue are shown over time. For eastern Bering Sea, Gulf of Alaska, northern California, and Pacific Northwest ecosystems, values are shown for 2004–2020 (i.e., over time periods ten years prior to the Pacific marine heatwave (“Blob”), over the duration of the heatwave, and post-heatwave). For the Gulf of Maine, values are depicted for 1999–2020 (i.e., over time periods ten years prior to the onset of an accelerated warming period for the Gulf of Maine, during the accelerated warming period and prior to a subsequent marine heatwave and noted spike in temperatures, and for years following the heatwave and during the temperature spike). For the northern Gulf of Mexico, values are shown for 1995–2020 (i.e., over time periods ten years prior to Hurricane Katrina, during the post-hurricane period prior to the Deepwater Horizon (DWH) oil spill, and for years following the DWH event).