Movement and habitat use by the spine-tail devil ray in the Eastern Pacific Ocean

Abstract

The devil-ray family Mobulidae (order Myliobatiformes) comprises wide-ranging, pelagic batoids, but little is known about their basic ecology. We present the first data on the long- distance movement of mobulid devil rays. We attached pop-up archival satellite tags to 13 individ- uals of the spine-tail devil ray Mobula japanica (disk width 199.5 ± 30.0 cm; mean ± SD) off Baja California Sur to examine their habitat movement patterns. Tags remained on the rays for 83 ± 52 d (mean ± SD). Although their primary prey undergo diel migrations from depths >100 m during the day to the surface at night, tagged individuals spent the majority of their time (89.5 ± 3.1% during the day and 96.8 ± 3.5% at night; mean ± SD) near the surface at a depth of ≤50 m in 20 to 30°C water. Thus, M. japanica likely forages at night and remains near the surface during the day, where warmer water temperatures likely confer a physiological advantage. Most (8 of 13) individuals moved from the tagging location in the southern Gulf of California to the Pacific coast of Baja California Sur, tracking published records of seasonal patterns in euphausiid abundance, similar to other top predators in the region. The depths and geographic regions occupied by M. japanica coincide with the focus of artisanal and industrial fisheries. This overlap with fisheries, when combined with the delayed maturity and low reproductive rates of devil rays, raises con- cerns of potentially damaging high bycatch mortality.