Signature of climate-induced changes in seafood species served in restaurants

Climate change is causing shifts in biogeography of marine species,
towards higher latitude, deeper waters, or following local temperature
gradients. Such species distribution changes are affecting global
fisheries through increasing the dominance of warmer-water preferred
species as ocean temperature increases. Previous modeling analyses
projected that climate-induced changes in seafood availability would
affect the entire seafood chain. However, observed climate impacts on
seafood retailers and consumers have rarely been demonstrated. Seafood
restaurants usually rely on the supply of locally caught species, and thus
the impacts of changing catches on the food they serve, and consequently
on their diners, may be reflected in their menus. In this study, 362
restaurant menus from Vancouver, British Columbia, Canada, were collated
and analyzed over four different time periods (1880–1960, 1961–1980,
1981–1996, and 2019–2021). Moreover, 148 present-day menus from two other
cities north (Anchorage, AK, USA) and south (Los Angeles, CA, USA) of
Vancouver were also collected. An index, herein called Mean Temperature of
Restaurant Seafood (MTRS), was calculated from the average temperature
preference of the species of seafood identified in the menus for each time
period or location. Overall, the MTRS of menus from Vancouver increased
from 10.7 ± 0.7 °C to 13.8 ± 1.0 °C (95% confidence intervals) between
1888–1960 and 2019–2021. Present-day MTRS was among the highest in Los
Angeles (16.5 ± 1.7 °C) and lowest in Anchorage (9.6 ± 1.0 °C). The
temporal and spatial variations in MTRS are significantly related to
observed patterns of average sea surface temperature and the Mean
Temperature of the Catch. This suggests that restaurant menus may be used
as a complementary information source regarding changes in marine
ecosystems and fisheries and the seafood sector’s responses to these
changes. This study also highlights the value of using unconventional
information sources and their applications in the detection of climate
impacts on oceans and their dependent human communities.