Regresar

Demographics and dynamics of the world’s largest known population of oceanic manta rays Mobula birostris in coastal Ecuador

Abstract:

Information on the life history and demographics of oceanic manta rays Mobula birostris remains scarce. Using photo-ID data, we describe the demographic structure, population size, and possible environmental drivers of the seasonal occurrence of M. birostris at Isla de la Plata and Bajo Copé, Ecuador. We identified a total of 2803 individuals from 3322 encounters over a period of 14 yr (2005−2018). The population sampled at these sites was significantly biased towards males (sex ratio 1F:1.67M) and only 12.9% of individuals were resighted. We used mark−resight models to estimate demographic parameters of the population, including superpopulation size, survival probability, entry/recruitment probability, and detection probability. We also evaluated how these parameters were related to environmental pbkp_redictors, such as El Niño− Southern Oscillation (ENSO), sea surface temperature (SST), and chlorophyll a (chl a). Mark− resight analyses indicated that SST, chl a, time, and sex, but not ENSO, were important pbkp_redictors of estimated population parameters. Entry probability peaked in 2012, which coincided with the lowest SST and highest chl a concentrations. The best-fit mark−resight model estimated a superpopulation size of 22 316 individuals, with annual estimated abundances of 949−7650 females and 5226−9340 males. Localised sampling of this highly mobile species limits the interpretations of mark−resight analyses, but provides lower bounds for total abundance that indicate the population of M. birostris in coastal Ecuador and Peru is likely the largest in the world.