In 1996–1998, this species was the second most abundant species in Manoel Luis State Marine Park; it was present in 69% of underwater visual census (UVC) samples and had a mean length of 30 cm (Rocha and Rosa 2001). On the Abrolhos Bank, the largest coral reef area in the south Atlantic, this species represents 28% of total fish biomass, and has shown 50% decline in the past five years (Francini-Filho 2005, Francini-Filho and Moura 2008).

In the southeastern part of its range (Arraial do Cabo), the biomass has declined by 60–70% over the last 15 years based on UVC and fishermen interviews (B. Ferreira pers comm. 2008). Scarus trispinosus densities obtained with UVC (n=418 summer months at six areas) in shallow rocky reefs of less than 10 m depth in southeastern Brazil had a mean value of 0.00018/m² (A. Bertoncini pers comm. 2008). In the northeast of Brazil in Baixo-sul baiano, an UVC (n=713 at five reef areas) in shallow reefs from 10 to 25 m depth revealed mean density values of 0.0018/m² (A. Bertoncini and C. Sampaio pers comm. 2008).

Decreasing