Pacific sardine (Sardinops sagax), also known as South American pilchard, is a neritic, coastal pelagic species caught at depths of about 40 m and forms large schools (Bystrom et al. 2023). Pacific sardine off the West Coast of North America is thought to consist of three subpopulations or stocks (Vrooman 1964): a northern (“cold”) stock (north Baja California to Alaska), a southern stock (outer coastal Baja California to southern California), and a Gulf of California stock determined by serological population studies (Hill et al. 2015). (Hid Coronel 2020) suggests that there are no genetic differences between the southern stock and the Gulf of California stock. Rather, the morphological differences among these stocks result from phenotypic plasticity in response to environmental adaptations. (Lecomte et al. 2004) theorizes that the population is not geographically structured but rather responds to a basin model, where, in times of population crash, the distribution contracts to its optimal range, which would explain the low genetic differentiation along its distribution. 

Given the uncertainty regarding stock structure and that INAPESCA assesses the Gulf of California population independently, this profile is structured around an assessment unit in the Gulf of California.