Abstract
Batoids comprise five of the seven most threatened families of sharks and rays. The East Asian endemic Naru eagle ray Aetobatus narutobiei is a large bodied ray whose estuarine habitat overlaps with an economically valuable bivalve fishery. In response to decreased bivalve yields, the government initiated a predator control program and as a result, Naru eagle rays have faced intense and targeted fishing pressure during the last two decades. The long-term impacts of the predator control program on the population of rays and bivalves and their balance in the ecosystem are unknown because the life history of the Naru eagle ray has not been characterized. To begin to fill these critical knowledge gaps, the reproductive life history of the Naru eagle was described. Females mature at a larger size than males and require nearly twice as many years to reach maturity (DW50, 952.0 mm vs. 764.2 mm; Age50, 6.0 years vs. 3.5 years). Both males and females reproduce annually and their reproductive cycles are synchronized and seasonal. Females have a single ovary and paired uteri, are viviparous, and reproduce via matrotrophic histotrophy. Mating occurs in August and September and gestation lasts approximately 12 months including a 9.5-month diapause that begins soon after mating and ends in June of the following year, leaving 2.5 months for embryos to complete development. Fecundity ranged from 1 to 7 embryos per brood (n = 158, mean ± SD = 3.36 ± 1.26) and was positively correlated with female disc width (linear regression; F = 105.73, d.f. = 151, P < 0.05). Naru eagle rays are vulnerable to overfishing because of their low fecundity, long reproductive cycle and long time to reach sexual maturity. Obligate embryonic diapause during overwintering and seasonal migrations is a survival strategy that benefits the adults and neonates. This research is a valuable resource to help guide science-based management, conservation and protection of the endemic Asian A. narutobiei and its nursery areas.
Highlights
Climate change and anthropogenic disturbances can have significant and deleterious effects on coastal ecosystems and regional biodiversity
Batoids are more threatened than sharks and chimeras (Dulvy et al, 2021) and they play an important role as mesopredators and energetic links in ecosystems, they have received comparatively little attention from researchers and policy makers compared to their more charismatic shark counterparts
Uterine eggs without macroscopic embryos contained within a tertiary egg envelope
Summary
Climate change and anthropogenic disturbances can have significant and deleterious effects on coastal ecosystems and regional biodiversity. According to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, 33.7% (387 of 1174) of sharks and rays are threatened with extinction (Dulvy et al, 2021). Large-bodied and shallow-water species are at the greatest risk of extinction, and five out of the seven most threatened families are batoids (i.e., rays, skates, guitarfish, and sawfish) (Dulvy et al, 2014). Batoids are more threatened than sharks and chimeras (Dulvy et al, 2021) and they play an important role as mesopredators and energetic links in ecosystems, they have received comparatively little attention from researchers and policy makers compared to their more charismatic shark counterparts. For endemic elasmobranchs with a narrow range, identification and preservation of critical habitat is an urgent conservation need
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
