This data set integrates findings of 16 years (2005 to 2020) of collaborative monitoring efforts across multiple institutions in the Gulf of California.The data encompasses information of 13 species of marine herbivorous fishes belonging to five families: Acanthuridae, Girellidae, Kyphosidae, Pomacentridae and Scaridae. This database presents 884 records of biomass from 15,542 visual censuses assessed by scuba diving in 34 localities (comprising 268 rocky and coral reefs sites). Visual censuses consisted of belt transects (250 m2, 100 m2, and 60 m2) laid parallel to the coastline preserving a similar depth profiles. Along these transects, trained underwater monitors, identified the species, recorded the abundance of all the adult individuals of the 13 targeted species and visually estimated the total length (cm) of each fish. The information for each transect in the database, is presented as the biomass (grams per square meter), which was estimated based on the size per individual as well as the weight-length relationship for each species, available on the literature. In the database is also integrated the information of the latitude and longitude of each locality, type of management, localities in the Gulf of California, institutions, the initial and final year of data, total number of years, as well as the mean, standard deviation, sample size, slope (annual rate of change), probability value, standard error and minimum and maximum value calculated for each species within each locality. This dataset represents a historical reference point for the condition of the 13 species found in the Gulf of California. It can be used to perform evaluations of how herbivorous fish communities have changed over time and across different locations. This is particularly relevant due to the influence of global changes leading to tropicalization in the study area. Furthermore, this information holds significance as it supplies essential insights to those responsible for the management of protected zones in the Gulf and the broader eastern tropical Pacific region. communities have changed over time and across different locations. This is particularly relevant due to the influence of global changes leading to tropicalization in the study area. Furthermore, this information holds significance as it supplies essential insights to those responsible for the management of protected zones 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.