Long-term biomass estimates for the central stock of northern anchovy (CSNA; Engraulis mordax) in the California Current Ecosystem are estimated from geospatial weighting of egg and larval data from winter/spring California Cooperative Oceanic Fisheries Investigations (CalCOFI) surveys (1951–2021). This is important, to avoid bias due to the nearshore concentration of CalCOFI sampling stations and the anchovy population tendency to contract into that area when abundances are low. While based on the core CalCOFI sampling area, estimates include the entire range of the CSNA, from northwestern Baja California, Mexico, to north of Point Reyes, California, and nearshore waters.

See MacCall et al. (2016) and Thayer et al. (2017) for complete details of methodology and justifications. Biomass estimates have been calculated through 2021 (Thayer et al. 2022), and as new survey data become available estimates are updated regularly (see Anchovy Biomass Estimates).