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.

Copies of publicly available restaurant menus from Vancouver (Canada), Los Angeles (USA) and Anchorage (USA) dated since the 19^th century were collected from the Internet and museum archives. Archives of menus from restaurants in Vancouver collected from The University of British Columbia (UBC) library, Victoria Island University library, the City of Vancouver Archives, and the Museum of Vancouver Archives were surveyed (N = 228). Only menus that have specified a year of publication or a range of years were recorded. The menus were categorized into three different time periods: 1888-1960, 1961-1980, and 1981-1996. In addition, a total of 134 present day (2019 -2021) menus from Vancouver, 72 menus from Los Angeles menus, and 76 from Anchorage were collected online using the restaurants’ websites or other websites where restaurant menus were made available publicly, including TripAdvisor(https://www.tripadvisor.ca/), KAYAK (https://www.ca.kayak.com/), and OpenTable (https://www.opentable.ca/). The name of the restaurant, year and the seafood specified in the name of the dish or food ingredients were recorded if the information was available on the menus.