Behaviour 2019
Coprophagy by herbivorous Caribbean fishes: quantifying species-specific rates and nutritional value
Hannah S. Rempel1,2, Abigail K. Siebert2, Jacey C. Van Wert3, Mark S. Edwards2, Kelly N. Bodwin2, Benjamin I. Ruttenberg2. 1University of Texas at Austin Marine Science Institute, Port Aransas, Texas, United States; 2California Polytechnic State University, San Luis Obispo, California, United States; 3University of California, Santa Barbara, Santa Barbara, California, United States

Parrotfishes (Labridae) and surgeonfishes (Acanthuridae) are important herbivores that primarily graze algae, indirectly benefiting reef-building corals that compete with algae. They are also known to feed on non-algal food sources, such as cyanobacteria; yet, to our knowledge, coprophagy (feces consumption) by these fishes has never before been documented in the Caribbean region. Based on surveys of foraging behavior, we found that six of the nine parrotfish species surveyed and all three surgeonfishes actively consume the feces of an abundant planktivore, Brown chromis (Chromis multilineata), and coprophagy rates varied by species. Based on surveys tracking feces, other fishes also consume these fecal pellets, but over 90% of observed instances of coprophagy were by parrotfishes and surgeonfishes. To assess the nutritional value of this behavior, we analyzed the composition of carbohydrates, lipids, proteins, and trace minerals in the feces and compared these to published values for algae and cyanobacteria. This study advances our understanding of the grazing dynamics of these major herbivores and the importance of coprophagy in nutrient cycling on coral reef ecosystems.