A comparison of feeding biomechanics between two parrotfish species from the Gulf of California

Parrotfish are amongst the most abundant teleost species in the Gulf of California, and yet their feeding ecology and the impact they have on the reef ecosystems in this region remain unknown. Here, a well-established computational model of jaw biomechanics in fishes (MandibLever 4.0) was used to simulate the mandibular dynamics during feeding of the two dominant reef-dwelling parrotfish species in the Gulf of California (Scarus ghobban and S. perrico), and to infer, to some extent, their potential ecological role. A total of 52 specimens were collected from six localities in La Paz Bay and the Los Cabos region between March and October 2015. The model predicted a greater jaw closing force and power in the bite of S. perrico, but a higher mandibular rotating velocity in S. ghobban. The calculated differences in their bite dynamics suggest that these two species may exploit different food resources, driven by food hardness. Moreover, the variation in their mandibular morphology and predicted feeding behavior might imply the presence in the Gulf of California of the two previously described functional groups found in reef-dwelling parrotfishes: excavators and scrapers. As an excavator, S. perrico would be functioning as one of the major agents of external bioerosion in the rocky reefs of the Gulf of California, whereas, as a scraper, S. ghobban would facilitate the reworking and hydrological transport of fine sediments. This work lays the foundation for future studies on the feeding ecology and impact of parrotfishes on the reefs of the Gulf of California.