Marine Heatwave Stress Test of Ecosystem-Based Fisheries Management in the Gulf of Alaska Pacific Cod Fishery

Steven J Barbeaux,Kirstin Holsman,Stephani Zador

doi:10.3389/fmars.2020.00703

Abstract

In 2014–2016 an unprecedented warming event in the North Pacific Ocean triggered changes in ecosystem of the Gulf of Alaska (GOA) impacting fisheries management. The marine heatwave was noteworthy in its geographical extent, depth range, and persistence, with evidence of shifts in species distribution and reduced productivity. In 2017 groundfish survey indicated that GOA Pacific cod (Gadus macrocephalus) had experienced a 71% decline in abundance from the previous 2015 survey. The GOA Pacific cod fishery supports a $103 million fishery which is 29% of the groundfish harvest value in the GOA. In this paper, we demonstrate that an increase in metabolic demand during this extended marine heatwave as well as a reduced prey supply can explain the decline in GOA Pacific cod biomass. Although increased mortality likely led to the decline in the Pacific cod population, historically low recruitment concurrent with the heatwave portends a slow recovery for the stock and gives a preview of impacts facing this region due to climate change. We evaluate the intersection of climate change with ecosystem-based fisheries management in the context of GOA Pacific cod with a description of the sensitivities of the ecosystem, how the changes in the ecosystem affected the Pacific cod stock, and a description of how the management system in the North Pacific handled this shock. We also provide suggestions on how fisheries management systems could be improved to better contend with the impacts of climate change such as the effects of heatwaves like that experienced in 2014–2016.

Highlights

Climate change is beginning to have a direct impact on marine resources globally (Poloczanska et al, 2013; Gattuso et al, 2015; Pecl et al, 2017; Barange et al, 2018) and current management tools must be able to adapt to future challenges that these impacts will bring (Busch et al, 2016; Holsman et al, 2019a,c; Karp et al, 2019)
The daily mean sea surface temperature data were processed through the R package heatwaveR (Schlegel and Smit, 2018) to obtain the marine heatwave cumulative intensity (MHCI) value (Hobday et al, 2016) where we defined a heatwave as 5 days or more with daily mean sea surface temperatures greater than the 90th percentile of the 1 January 1983 through 31 December 2012 time series
Many ecosystem indicators representing physical processes such as climate and oceanography in the Gulf of Alaska (GOA) showed strong shifts in signal direction or exhibited anomalous values beginning in early 2014 that remained relatively unchanged through the marine heatwave

Summary

Introduction

Climate change is beginning to have a direct impact on marine resources globally (Poloczanska et al, 2013; Gattuso et al, 2015; Pecl et al, 2017; Barange et al, 2018) and current management tools must be able to adapt to future challenges that these impacts will bring (Busch et al, 2016; Holsman et al, 2019a,c; Karp et al, 2019). Recoveries from middens on Sanak Island in the Western GOA show a long history (at least 4,500 years) of exploitation and reveal fluctuations in Pacific cod size distribution which (Betts et al, 2011) tie to changes in abundance due to climate variability. Over this period, warm climate conditions appear to have led to lower abundance with fewer small Pacific cod in the exploited population; zooarchaeological methods are unable to resolve the overall magnitude or timescale over which rapid population changes occur. Pacific cod population dynamics appear to include periodic largemagnitude fluctuations

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Results

Conclusion