Distribución estival y abundancia de la gran manta raya (Mobula mobular) en el mar Adriático: datos de base para un marco de gestión iterativo

The giant devil ray (Mobula mobular) is a poorly understood protected endemic species of the eastern Atlantic-Mediterranean region. However, to date there are no range-wide management actions in place. This paper provides the first overview of the summer distribution and abundance of this species and other Myliobatiformes within the Adriatic Sea based on an aerial survey. Although the survey´s primary targets were cetaceans and sea turtles, the study showed that it was possible to use the survey to monitor other species. Abundance estimates are derived using conventional distance sampling analysis. Giant devil rays were observed mainly in the central-southern Adriatic (88% of total sightings). A total of 1595 giant devil rays were estimated in the central-southern Adriatic Sea [coefficient of variation(CV)=25%, uncorrected estimate for perception and availability bias]. When corrected for availability bias the number of specimens was estimated at 3255 (CV=56%). Population growth rate was estimated using life history traits and a sensitivity analysis was conducted to evaluate the benefit of improving biological knowledge on this data-poor species. A power analysis showed that a long-term commitment to an aerial survey would be necessary to monitor population trends. Conservation implications and future work, including how the study could be used to conduct an ecological risk assessment are discussed.La manta raya gigante (Mobula mobular) es una especie endémica protegida poco conocida de la región del Atlántico oriental-Mediterráneo. Sin embargo hasta la fecha no hay acciones de gestión que cubran todo su rango. Este artículo proporciona la primera visión de conjunto de la distribución y abundancia estival de esta especie y otras Myliobatiformes en el mar Adriático basada en un censo aéreo. Aunque los objetivos principales del censo eran cetáceos y tortugas marinas, el estudio mostró que era posible usar el censo para monitorizar otras especies. Las estimas de abundancia se derivaron utilizando análisis convencional de muestreo de distancias. Las manta rayas gigantes se observaron principalmente en el Adriático central y sur (88% de los avistamientos totales). Se estimaron un total de 1595 mantas rayas gigantes en el mar Adriático central-sur (CV=25%, estima no corregida para los sesgos de percepción y de disponibilidad). Cuando se corrigió para el sesgo de disponibilidad el número de especímenes se estimó en 3255 (CV=56%). La tasa de crecimiento de la población se estimó usando aspectos de la historia natural y se realizó un análisis de sensibilidad para evaluar el beneficio de mejorar el conocimiento biológico de esta especie de la que hay tan pocos datos. Un análisis de potencia mostró que sería necesario un compromiso a largo plazo para realizar censos aéreos para monitorizar las tendencias de la población. Se discuten las implicaciones para la conservación y trabajo futuro, incluyendo cómo se podría utilizar este estudio para llevar a cabo una evaluación ecológica de riesgo

Summer distribution and abundance of the giant devil ray (<em>Mobula mobular</em>) in the Adriatic Sea: Baseline data for an iterative management framework

The giant devil ray (Mobula mobular) is a poorly understood protected endemic species of the eastern Atlantic-Mediterranean region. However, to date there are no range-wide management actions in place. This paper provides the first overview of the summer distribution and abundance of this species and other Myliobatiformes within the Adriatic Sea based on an aerial survey. Although the survey´s primary targets were cetaceans and sea turtles, the study showed that it was possible to use the survey to monitor other species. Abundance estimates are derived using conventional distance sampling analysis. Giant devil rays were observed mainly in the central-southern Adriatic (88% of total sightings). A total of 1595 giant devil rays were estimated in the central-southern Adriatic Sea [coefficient of variation(CV)=25%, uncorrected estimate for perception and availability bias]. When corrected for availability bias the number of specimens was estimated at 3255 (CV=56%). Population growth rate was estimated using life history traits and a sensitivity analysis was conducted to evaluate the benefit of improving biological knowledge on this data-poor species. A power analysis showed that a long-term commitment to an aerial survey would be necessary to monitor population trends. Conservation implications and future work, including how the study could be used to conduct an ecological risk assessment are discussed