Slender thread herring (Opisthonema bulleri) is found from Magdalena Bay in the Gulf of California, Mexico to northern Peru (Berry and Barrett 1963). In the Sonora region, this species is captured in a very low proportion (as compared to the dominant species, the Pacific thread herring). In the southern Gulf, in Sinaloa and Nayarit, the proportion of the three Ophistonema species is more similar and assessment is conducted separately (Morgan et al. 2016) and through biological parameters, these two areas have been ratified as separated stocks (Ruiz Domínguez 2019). Therefore, an assessment unit is considered in Sinaloa and Nayarit for slender thread herring. Management considers this with other two Opisthonema species (O. libertate and O. medirastre) under the same resource: "Sardina crinuda" (DOF 2022).