Future Climate Impacts on the Pelagic and Coastal Fisheries of Hawai‘i

Hawai‘i has the sixth-largest commercial fish landings in the country, and the industry
is significant economically, socially, and culturally to the state. As the only oceanic state, many people rely on the ocean for their livelihood, from subsistence living to commercial enterprises. Hawaiian fisheries are comprised of two primary types: pelagic long-line fisheries and coastal/reef fisheries. How the health and productivity of fisheries evolve due to interannual-to-decadal variability and climate change is an existential question for this state. Over the past thirty years, the variability of extreme events has likely increased and will further increase in the future (prolonged marine heat waves, potentially stronger El Niño impacts, etc.); however, the climate itself has not yet significantly shifted. Two important questions related to climate change are: (i) how will interannual-to-decadal variability change over the coming decades; (ii) and, when will climate change emerge as the dominant signal? Each of these issues impact the pelagic and reef fisheries in different ways. The current pelagic longline fishery is located northeast of the islands within the subtropical gyre.

Over the next decades, the variability of the gyre (including prolonged heat waves, increased stratification, etc.) will be the primary stressor on the fishery, particularly at the lower trophic levels (leaving human fishing from discussion). However, as climate change emerges, the gyre is projected to expand poleward and eastward, making it likely that fishers move closer to California than Hawai‘i. For the reef fisheries, variability over the next decades may subject them to changes in ocean circulation, marine heat waves, oscillating from low to high nutrients, enhanced vertical mixing, etc. As climate change emerges at the reef, the primary stressors may include alteration of the mean circulation and water masses, increased acidification, and reduction in retained larvae. We propose to utilize a suite of Earth System Models (LENS and CMIP6) with a regional, coupled physical and biogeochemical
model (ROMS/COBALT) to identify the regional impacts of global variability and climate change. These models will be used to force both pelagic and coastal/reef fishery models to understand the physical and biogeochemical drivers that change the fishery (marine health, stock assessment, etc.) and to make projections for future planning and resilience.

This proposal is an end-to-end research-based approach to identify the role of interannual-to-decadal variability and climate change forcing on Hawaiian fisheries. It addresses the goal of CPO by advancing our scientific understanding, decision support research, and out- reach/education (including two Ph.D. students) of Earth’s climate system. Our state-of-the- art model hierarchy from planetary to coastal scale provides a unique toolset for the scientific community to evaluate regional variability and climate change in the context of climate scenarios. By utilizing two fishery models, we will broaden CPO’s success by quantitatively addressing the climate impacts on marine health, fishery productivity, and ultimately, the
sustainability and resiliency of the marine ecosystem for the critical fisheries of Hawai‘i.

Climate Risk Area: Marine Ecosystems