Marine heatwaves exacerbate climate change impacts for fisheries in the northeast Pacific - PubMed (original) (raw)

Marine heatwaves exacerbate climate change impacts for fisheries in the northeast Pacific

William W L Cheung et al. Sci Rep. 2020.

Abstract

Marine heatwaves (MHWs) have occurred in all ocean basins with severe negative impacts on coastal and ocean ecosystems. The northeast Pacific 2013-2015 MHW in particular received major societal concerns. Yet, our knowledge about how MHWs impact fish stocks is limited. Here, we combine outputs from a large ensemble simulation of an Earth system model with a fish impact model to simulate responses of major northeast Pacific fish stocks to MHWs. We show that MHWs cause biomass decrease and shifts in biogeography of fish stocks that are at least four times faster and bigger in magnitude than the effects of decadal-scale mean changes throughout the 21st century. With MHWs, we project a doubling of impact levels by 2050 amongst the most important fisheries species over previous assessments that focus only on long-term climate change. Our results underscore the additional challenges from MHWs for fisheries and their management under climate change.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1

Figure 1

Average annual fisheries catches of the 22 studied fish stocks from 1981 to 2015 in the northeast Pacific Ocean and the three large marine ecosystems therein. Catches data were obtained from the Sea Around Us fisheries database (

www.seaaroundus.org

). The boundary of the northeast Pacific Ocean is based on the United Nations’ Food and Agriculture Organization Statistical Area 67. The large marine ecosystems include: EBS - Eastern Bering Sea, GoA - Gulf of Alaska, and CC - California Current.

Figure 2

Figure 2

Schematic diagram explaining the characterization of Marine Heatwaves (MHWs) and their impacts on fish stocks. (a) The characterization of MHWs based on outputs from the 10 ensemble member projections of the GFDL ESM2M and (b) their impacts on biomass of the sockeye salmon (Oncorhynchus nerka) in the Gulf of Alaska large marine ecosystem. The red vertical bars in both panels indicate MHW events. Biomass changes are given as changes relative to 1986 to 2005.

Figure 3

Figure 3

Projected changes in sea surface temperature (A,B) and the impact indicators (biomass, latitudinal centroid and depth centroid; C–H) of the 22 studied fish stocks in the three large marine ecosystems (Eastern Bering Sea - EBS, Gulf of Alaska - GoA, California Current - CC) of the northeast Pacific during MHWs (left panels) and due to long-term climate change from 1981 to 2100 (right panels). Changes in sea surface temperature and impact indicators during MHWs were expressed relative to the spline-smoothed ensemble-mean of the same time period. In contrast, long-term climate changes were calculated from linear regressions over the 1981–2100 period, with the rate of change (slope of the regression) expressed as change per decade. Negative depth centroid shifts in G-H indicate species’ average distribution that were projected to be deeper.

Figure 4

Figure 4

Projected mean changes in biomass, latitudinal and depth centroid of the 22 exploited marine fish stocks in the Eastern Bering Sea (EBS), Gulf of Alaska (GoA) and California Current (CC) during MHW years. NA - not available in catch record between 2006 and 2015.The different colour scales represent the projected changes in biomass, latitudinal centroid and depth centroid. Stripping of a cell represents changes at a significant level of below 0.05.

Figure 5

Figure 5

Projected time-series of changes in sea surface temperature (SST) (A–C), biomass (D–F) and latitudinal centroid (G–I): Pacific cod (Gadus macrocephalus) (D,G), sockeye salmon (Oncorhynchus nerka) (E,H) and Californian anchovy (Engraulis mordax) (F,I)) in the Eastern Bering Sea (EBS), Gulf of Alaska (GoA) and California Current (CC). The solid lines represent the average values across the 10 ensemble member simulations (smoothed with a cubic spline function); blue-colored triangles represent values during MHW years; the different intensity of blue color represents different ensemble member simulations (see Figs. S1–12 for results for all the large marine ecosystems and studied fish stocks).

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