Eat whole and less often ontogenetic shift reveals size specialization on kelp bass by the California moray eel, Gymnothorax mordax

• Published in: Oecologia Vol. 188; no. 3; pp. 875 - 887
• Main Authors: Higgins, Benjamin A., Law, Chris J., Mehta, Rita S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Science + Business Media 01.11.2018; Springer Berlin Heidelberg; Springer; Springer Nature B.V
• Subjects: Allometry; Analysis; Animal morphology; Animals; Bass; Biomedical and Life Sciences; Biometry; Body size; California; Catadromous fishes; COMMUNITY ECOLOGY – ORIGINAL RESEARCH; Diet; Ecology; Ecosystem; Ecosystem biology; Ecosystems; Eels; Fishes; Force measurement; Forces (mechanics); Forest ecology; Forest ecosystems; Gymnothorax mordax; Head; Hydrology/Water Resources; Independence Day; Interspecific relationships; Islands; Kelp; Length; Life Sciences; Marine ecosystems; Marine fishes; Muraenidae; Ontogeny; Paralabrax clathratus; Plant Sciences; Predation; Predators; Predatory Behavior; Prey; Scaling; Specialization; Stomach; Stomach content; Terrestrial ecosystems; Variation; California; United States > US; Bite force; Kelp bass; Predator–prey size relationships; Dietary specialization; Morays
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-018-4260-x

Despite the importance of predation in many ecosystems, gaps remain in our understanding of nocturnal marine predators. Although the kelp forests of Southern California are some of the most well-studied ecosystems, California morays, Gymnothorax mordax, are predominately nocturnal predators that have remained largely unstudied and their predatory effects on the kelp forest ecosystem are unknown. We use a multi-year data set to examine the dietary breadth of G. mordax and to determine the functional role of this predator. We also quantify bite force to examine the potential performance limitations of morays in exploiting prey. Stomach content analyses and linear selectivity index values indicate that G. mordax specializes on kelp bass, Paralabrax clathratus. Average size of kelp bass consumed varies across years, suggesting that morays respond to fluctuations in prey size availability. The scaling relationship of kelp bass standard length and moray head length reveals an ontogenetic shift, where maximum prey size increases with moray size and small prey are dropped from the diet of larger individuals. Moray bite force exhibited strong positive allometry with moray head size, suggesting that larger morays exhibit greater bite forces for their head and body size. However, we found no relationship between prey size and bite force, suggesting that a disproportional increase in bite force does not facilitate the consumption of disproportionately larger prey. Our results indicate that while G. mordax of Catalina Island is a dietary specialist, it is capable of exhibiting functional shifts in prey size and species based on their abundance.