Projected Shifts in 21st Century Sardine Distribution and Catch in the California Current

Abstract

Predicting changes in the abundance and distribution of small pelagic fish species in response to anthropogenic climate forcing is of paramount importance due to the ecological and socioeconomic importance of these species, especially in eastern boundary current upwelling regions. Coastal upwelling systems are notorious for the wide range of spatial (from local to basin) and temporal (from days to decades) scales influencing their physical and biogeochemical environments and, thus, forage fish habitat. Bridging those scales can be achieved by using high-resolution regional models that integrate global climate forcing downscaled from coarser resolution earth system models. Here, “end-to-end” projections for 21st century sardine population dynamics and catch in the California Current system (CCS) are generated by coupling three dynamically downscaled earth system model solutions to an individual-based fish model and an agent-based fishing fleet model. Simulated sardine population biomass during 2000–2100 exhibits primarily low-frequency (decadal) variability, and a progressive poleward shift driven by thermal habitat preference. The magnitude of poleward displacement varies noticeably under lower and higher warming conditions (500 and 800 km, respectively). Following the redistribution of the sardine population, catch is projected to increase by 50–70% in the northern CCS and decrease by 30–70% in the southern and central CCS. However, the late-century increase in sardine abundance (and hence, catch) in the northern CCS exhibits a large ensemble spread and is not statistically identical across the three downscaled projections. Overall, the results illustrate the benefit of using dynamical downscaling from multiple earth system models as input to high-resolution regional end-to-end (“physics to fish”) models for projecting population responses of higher trophic organisms to global climate change.

Climate Change Impacts on Eastern Boundary Upwelling Systems

“…In the CalCS, northward shifts in sardine distribution under climate change may reduce fish catch in some regions while increasing it in 4.14 Bograd et al , . others (Fiechter et al 2021, Smith et al 2021, while also altering predator reliance on individual species (Petatán-Ramírez et al 2019). On the other hand, projected increases in upwelling may mitigate warming trends (Seabra et al 2019, Varela et al 2022, providing areas of climate refugia for EBUS fauna (Hu & Guillemin 2016, Lourenço et al 2016, Barceló et al 2018.…”

Recommendations for quantifying and reducing uncertainty in climate projections of species distributions

“…ESMs were downscaled using the Regional Ocean Modelling System (ROMS) coupled with a biogeochemical model (NEMUCSC) (Fiechter et al, 2018(Fiechter et al, , 2021 based on the North Pacific Ecosystem Model for Understanding Regional Oceanography (NEMURO) (Kishi et al, 2007). The ROMS domain spans the CCS from 30 to 48°N and from the coast to 134°W at 0.1° horizontal resolution with 42 terrain-following vertical layers (Figure 2).…”

Social-ecological vulnerability of fishing communities to climate change: A U.S. West Coast case study

“…As species’ distributions shift [ 5 , 6 , 99 ], communities may be able to adapt and target species that were previously not easily accessible [ 100 ]. For example, predicted shifts in Pacific sardine ( Sardinops sagax ) distribution could lead to increased catch of this species in the northernly portion of the California Current system [ 66 , 101 ], a potentially adaptative response as other highly at risk species that these communities target become less accessible. However, as noted, certain socioeconomic factors (see [ 102 ]) and/or management regulations and flexibility [ 100 , 103 ] may influence fisher ability to take advantage of such shifts.…”

“…We used a California Current configuration of the Regional Ocean Modeling System (ROMS) coupled with a biogeochemical model (NEMUCSC) to simulate historical and future climate conditions for temperature, pH, chlorophyll, or oxygen within species geographic ranges [ 66 , 67 ]. The ROMS-NEMUCSC model domain spans 30–48˚N and from the coast to 134˚W with a horizontal resolution of 0.1 degrees (~10 km) and 42 terrain-following vertical levels.…”