Activity Patterns, Diet, and Shelter Site Use for Two Species of Moray Eels, Gymnothorax moringa and Gymnothorax vicinus, in Belize

Abstract

Activity patterns, diet, and shelter site use were compared between two species of moray eels, the spotted moray, Gymnothorax moringa, and the purplemouth moray, Gymnothorax vicinus, in the shallow backreef habitat of the Belize Barrier Reef. We tracked eels tagged with acoustic transmitter tags, analyzed stomach contents, and surveyed shelter sites in a 150-m by 250-m survey area of patch reefs and coral rubble. The study site supported primarily subadult to early adult eels (379–947 mm TL). We made 490 G. moringa and 344 G. vicinus sightings in 74 census days. Shelter site use was similar for both species. Gymnothorax moringa left shelters nearly twice as often as G. vicinus (62.5% of nights vs 36.4%). Both species moved primarily at night and ranged less than 10 m to approximately 100 m from shelter for periods less than 1 h to more than 9 h. Forays were mainly in the open grassbed away from patch reefs, rubble, or other shelter. Gymnothorax moringa fed nearly twice as often as G. vicinus (39.4% empty stomachs versus 70.0%), consistent with the difference in activity patterns of tagged fish. Prey included fishes (primarily wrasses), small crabs, and octopus; however, G. moringa specialized on small crabs, and G. vicinus specialized on fish. Gymnothorax vicinus moved and fed primarily on nights with inclement weather, whereas G. moringa did so on both calm and inclement nights. Fish consumption increased on inclement nights for both species, and crab consumption increased on calm nights. Piscivory by G. vicinus appears to have been enhanced by their feeding on inclement nights.