Diet breadth and overlap in the Family Molidae

Marine sunfishes (also known as molids) of the Family Molidae are widely distributed from tropical to temperate waters and are typically recognized as predators of gelatinous plankton almost exclusively. Despite similar morphological features and behaviors, the trophic ecology and potential interactions among species of molids remain largely unknown. We reviewed literature on the diets of each species and conducted diet analyses of three species sampled off the east coast of Taiwan. We examined diet separation among sympatric species—ocean sunfish Mola mola, bumphead sunfish Mola alexandrini, and sharptail sunfish Masturus lanceolatus—through stomach content and stable isotope analyses. A literature review revealed that the Family Molidae exhibits broader diets than previously characterized. Mola mola, M. alexandrini, and M. tecta consume prey from epi/mesopelagic environments, while M. lanceolatus and slender sunfish Ranzania laevis consume prey from both epi/mesopelagic environments and benthic habitats. No gelatinous prey was found in the stomachs of R. laevis. Off Taiwan, M. mola and M. alexandrini had similar and relatively narrow diet breadths, primarily feeding on scyphozoans, suggesting similar trophic niches. In contrast, M. lanceolatus displayed a broader diet, mainly consuming tunicates and augmenting their diet from epi- and mesopelagic, coastal, and benthic habitats. Dietary differences between M. lanceolatus and the other species might be linked to morphological differences such as gape size and eye length. Mola mola and M. alexandrini tend to have larger gapes and eyes and our diet analysis shows that they forage on larger sized prey and at greater depths.