Abstract
Munk’s pygmy devil rays (Mobula munkiana) are medium-size, zooplanktivorous filter feeding, elasmobranchs characterized by aggregative behavior, low fecundity and delayed reproduction. These traits make them susceptible to targeted and by-catch fisheries and are listed as Vulnerable on the IUCN Red List. Multiple studies have examined fisheries impacts, but nursery areas or foraging neonate and juvenile concentrations have not been examined. This study describes the first nursery area for M. munkiana at Espiritu Santo Archipelago, Mexico. We examined spatial use of a shallow bay during 22 consecutive months in relation to environmental patterns using traditional tagging (n = 95) and acoustic telemetry (n = 7). Neonates and juveniles comprised 84% of tagged individuals and their residency index was significantly greater inside than outside the bay; spending a maximum of 145 consecutive days within the bay. Observations of near-term pregnant females, mating behavior, and neonates indicate an April to June pupping period. Anecdotal photograph review indicated that the nursery area is used by neonates and juveniles across years. These findings confirm, for the first time, the existence of nursery areas for Munk’s pygmy devil rays and the potential importance of shallow bays during early life stages for the conservation of this species.
Highlights
Nursery areas have been shown to be important for many elasmobranch s pecies[1,2]
We found significantly greater detections during the daytime at the receiver placed in a deeper area within Ensenada Grande, RS2 (26 m depth) (U = 359.39, P < 0.05) with almost no detections during nighttime when M. munkiana appear to move to shallower areas
Our results indicate that M. munkiana utilize nursery areas following the definition proposed for elasmobranch nursery areas
Summary
Nursery areas have been shown to be important for many elasmobranch s pecies[1,2]. These discrete areas have biotic and abiotic features that can be important for pupping and for enhancing the survival of neonates, and juveniles[2]. Mobulids (manta and devil rays) are planktivorous filter feeders with vulnerable life h istories[14,15] that include the lowest fecundity of all elasmobranchs (one pup per litter)[16,17], and delayed, aplacental viviparous matrotrophic reproduction cycles of 1–3 y ears[18,19,20,21]. Such low reproductive rates make mobulids extremely vulnerable to anthropogenic impacts including targeted small-scale fisheries[18,22,23] and bycatch in small- and large-scale fisheries[22,24]. While the species is nationally protected in Mexican waters under the NOM-029PESC-2006 and NOM-059-SEMARNAT-2010 regulations, illegal targeted fishing still exists in several areas in the Gulf of California[33]
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