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Environmental characteristics associated with the presence of the Spinetail Devil Ray (Mobula mobular) in the Eastern Tropical Pacific
In the eastern Pacific Ocean, the tropical tuna purse-seine fishery incidentally captures high
numbers of five mobulid bycatch species; all of which are classified as mortalities by the
Inter-American Tropical Tuna Commission due to uncertainties in post-release mortality
rates. To date, the factors (operational or environmental) leading to the capture of these
species by the fishery have not been well studied. Here, we developed Generalized Additive
Models for fisheries observer data to analyze the relationships between the presence/
absence of Mobula mobular bycatch and oceanographic conditions, the spatial and temporal variability in fishing location, and the set type (associated with dolphins, free-swimming
tuna schools or floating objects). Our results suggest that chlorophyll concentration and sea
surface height are the most important variables to describe the presence of M. mobular in
conjunction with geographic location (latitude and longitude) and set type. Presence of the
species was predicted in waters with chlorophyll concentrations between 0.5–1 mg�m-3 and
with sea surface height values close to 0; which indicates direct relationships with productive
upwelling systems. Seasonally, M. mobular was observed more frequently during December-January and August-September. We also found the highest probability of presence
observed in School sets, followed by Dolphin sets. Three areas were observed as important
hotspots: the area close to the coastal upwelling of northern Peru, the area west to Islands
Colon Archipelago (Galapagos) and the area close to the Costa Rica Dome. This information is crucial to identify the mobulids habitat and hotspots that could be managed and protected under dynamic spatial management measures to reduce the mortality of mobulid
rays in the eastern Pacific purse-seine fishery and, hence, ensure the sustainability of the
populations of these iconic species