Through collaborative monitoring involving multiple academic, government, and civil institutions over a span of 16 years (2005 to 2020), we compiled 884 records of the density of 13 species of marine herbivorous fishes. The data was collected through 15,542 visual censuses conducted by scuba diving in 34 localities, encompassing 268 rocky and coral reef sites. These censuses utilized belt transects (250 m², 100 m², and 60 m²) parallel to the coastline at similar depth profiles.Trained underwater monitors recorded abundances of all adult individuals of the 13 targeted species along the transects. The information for each transect in the database is presented as the average fish density (individuals per square meter), estimated based on the abundance for each species. The database integrates information on latitude, longitude, type of management, localities in the Gulf of California, institutions, initial and final years of data collection, total number of years, as well as mean, standard deviation, sample size, slope (annual rate of change), probability value, standard error, and minimum and maximum values calculated for each species within each locality.This dataset serves as a historical benchmark for assessing the status of 13 species in the Gulf of California. It enables the examination of changes in herbivorous fish communities over time and across various locations, which is crucial given the impact of global changes leading to tropicalization in the study area. The data is particularly important for providing valuable insights to those managing protected areas in the Gulf and the broader eastern tropical Pacific region.

Further funding information: The work of ECO: Ecosistemas y Conservación was supported by: Fondo Mexicano para la Conservación de la Naturaleza, Award Number: M1901016. The work of COBI and PANGAS initiative was supported by: Funder: Conservation Leadership Programme.* Niparaja was supported by Fondo Mexicano para la Conservación de la Naturaleza, The David and Lucile Packard Foundation, Walton Family Foundation, Paul M Angell Family Foundation and the Waterloo Foundation. All institutions thank to Comisión Nacional de Áreas Protegidas for support for the development of monitoring in protected áreas.