Declines in fish population density have been documented for several common Sacramento—San Joaquin Delta fish species attendant with apparent declines in biomass. However, previous studies have not examined possible changes to the size structure of the remaining fish community. Normalized biomass spectra (NBS) slopes reflect the size structure of a community, and NBS heights reflect the total ecosystem capacity. However, prior studies have shown fish community NBS slopes are resistant to changes associated with declining productivity, leading researchers to speculate that NBS slopes are regulated by strong internal compensatory mechanisms. In this study I examine NBS parameters derived from data from the fish salvage facilities of the State Water Project and Central Valley Project for 1993-2019, covering a well-studied decline for some abundant delta fish species (the Pelagic Organism Decline; POD). As a second line of inquiry, I examined whether NBS slopes were associated with variation in Sacramento—San Joaquin Delta outflow and water export volume since both variables have shown previous associations with salvage of age-0 fish and recruitment pulses for several fish species.