Devil in the details: growth, productivity, and extinction risk of a data-sparse devil ray

Abstract

1Devil rays (Mobula spp.) face rapidly intensifying shing pressure to meet the ongoing interna-2 tional trade and demand for their gill plates.is has been exacerbated by trade regulation of 3 manta ray gill plates following their 2014 CITES listing. Furthermore, the paucity of information 4 on growth, mortality, and shing e ort for devil rays make quantifying population growth rates 5 and extinction risk challenging. Here, we use a published size-at-age dataset for a large-bodied 6 devil ray species, the Spinetail Devil Ray (Mobula japanica), to estimate somatic growth rates, 7 age at maturity, maximum age and natural and shing mortality. From these estimates, we go 8 on to calculate a plausible distribution of the maximum intrinsic population growth rate (r max ) 9 and place the productivity of this large devil ray in context by comparing it to 95 other chon-10 drichthyan species. We nd evidence that larger devil rays have low somatic growth rate, lowAll rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/043885 doi: bioRxiv preprint first posted online Mar. 17, 2016; annual reproductive output, and low maximum population growth rates, suggesting they have 12 low productivity. Devil ray maximum intrinsic population growth rate (r max ) is very similar to 13 that of manta rays, indicating devil rays can potentially be driven to local extinction at low levels 14 of shing mortality. We show that shing rates of a small-scale artisanal Mexican shery were 15 up to three times greater than the natural mortality rate, and twice as high as our estimate of 16 r max , and therefore unsustainable. Our approach can be applied to assess the limits of shing 17 and extinction risk of any species with indeterminate growth, even with sparse size-at-age data.

Trophic overlap in mobulid rays: insights from stable isotope analysis

“…Our findings contribute to a limited but growing body of knowledge on the habitat use and ecology of mobulid rays, which are highly vulnerable to exploitation due to their demographic characteristics (Dulvy et al 2014, Pardo et al 2016. Both bycatch and targeted fisheries appear to contribute to global declines in mobulid abundance (Ward-Paige et al 2013, White et al 2015, Croll et al 2016.…”

“…Mobulid rays are vulnerable to incidental capture in gill nets, purse seines, trawls, and even long lines (Croll et al 2016). Moreover, their low annual reproductive output and conservative demographic characteristics make them highly susceptible to fisheries-induced population declines (Dulvy et al 2014, Pardo et al 2016, even when catch rates are low. Understanding horizontal and vertical habitat use, which are likely driven by foraging in many cases, can help determine when mobulid rays are most vulnerable to incidental capture in fisheries and can aid in the development of bycatch mitigation measures (Stewart et al 2016b).…”

Fishing and trade of devil rays (Mobula spp.) in the Bay of Bengal, Bangladesh: Insights from fishers’ knowledge

“…Devil rays are susceptible to both direct and indirect fishing effects, including targeted fishing, bycatch, boat strike and ghost fishing (Canese et al, 2011; Couturier et al, 2012; Pardo et al, 2016). Such fishing threats and their life history strategy of high mobility (trans‐boundary stocks), slow reproductive rates ( k ‐selected) and low rate of population increase, have led to a global need for conservation (Couturier et al, 2012; Dulvy et al, 2014; Croll et al, 2016; Alfaro‐Cordova et al, 2017; Lawson et al, 2017; Stewart et al, 2018).…”

Seasonal aggregation and diel activity by the sicklefin devil ray Mobula tarapacana off a small, equatorial outcrop of the Mid‐Atlantic Ridge

“…Mobula tarapacana is listed as Vulnerable by the IUCN (Pardo et al, 2016b). There is a general lack of information on the life history of Mobulidae, thus several species are classified under some level of threat (Croll et al, 2015;Dulvy et al, 2014;Lawson et al, 2017;Pardo et al, 2016a). In Brazil, the capture of all mobulid species is prohibited (MPA/MMA, 2013), but they are occasionally caught as bycatch by the Brazilian tuna fishery (Gadig & Sampaio, 2002;Mendonça et al, 2012;Viana et al 2013).…”