Michelle Carpenter – Marine Action Research
Robert Perryman – Marine Action Research
Nakia Cullain – Marine Action Research
Charles Griffiths – Marine Action Research
Andrea Marshall – Marine Action Research
The reef manta ray, Mobula alfredi, is an iconic, economically important species in Mozambique that faces a high risk of local extinction. Manta rays have the largest brain to body size ratio of all fish with evident intelligence in behaviours such as complex courting events and cooperative feeding. As mobulid rays, they possess cephalic fins; horn-like structures on the face which aid in filter-feeding and can be rolled up during swimming. However, manta rays use cephalic fins across several behaviours suggesting possible sensory, communicative, or mechanical functions. These structures are also impacted by unsustainable fishing methods such as ensnaring by gill netting and long lines. The focus of this study is to determine if manta rays use cephalic fins in response to biotic or abiotic stimuli unrelated to feeding. As one of the first behavioural studies ever conducted on in situ wild reef manta rays and the first of its kind in Mozambique, data is largely preliminary, to be expanded on in subsequent field seasons. Manned and remote videographic observations have been collected via SCUBA diving on a cleaning station for two field seasons, 2018 and 2019. Focal animal sampling was used to investigate and compare movements of cephalic fins in various settings. Videos include the presence or absence of humans, and single or multiple individuals during various cleaning, courting, and swimming states. A randomly selected 5-min interval from each video was processed in the BORIS software for frame by frame analysis. Anecdotal evidence suggests differences in the use of cephalic fins in social interactions with other individuals. Preliminary results convey a diverse range of motions suggesting that these structures play an even more complex role than previously known. Acquiring knowledge about the complexity of these charismatic animals will increase awareness and hopefully stimulate incentives for protection.