Abstract:The fishery for mobulid rays, also known as devil rays, has been practiced in the Bohol Sea for over a century yet very little is known about its history and characteristics. This study provides the first detailed description of the mobulid ray fishery in the Bohol Sea, Philippines. It describes the history and evolution of the fishery from the 19th century to 2013. It characterizes the fishery based on the species targeted, gears used, the organization, catch distribution, processing, monetary value, and the … Show more
“…It is unclear why M. alfredi were not caught together with the other mobulids, but this trend may indicate habitat partitioning (Marshall et al, 2009;Deakos et al, 2011;Rambahiniarison et al, 2016), or local extirpation. Historical fishing grounds were closer to the coast than at present (Acebes and Tull, 2016), covering a habitat with different oceanographic characteristics (i.e., 0-500 m depth, slower currents in historical fishing grounds). Although M. alfredi is not as coastal as assumed in the past (Jaine et al, 2014), previous local population extinction could explain its current absence among the landed species.…”
Section: Mobulids In the Bohol Seamentioning
confidence: 97%
“…In the Bohol Sea, Philippines, direct fisheries have exploited mobulids for local consumption and gill rakers export for over a century (Fowler et al, 2002;Rayos et al, 2012;Acebes and Tull, 2016), and are now banned since April 2017 after the implementation of the CITES listing. In the municipality of Jagna, in the south-east of the island of Bohol, industrialization of the fishing fleet in the 1970's transformed a traditional coastal sailing harpoon-based fishery into a motorized offshore driftnet practice (Acebes and Tull, 2016).…”
Section: Introductionmentioning
confidence: 99%
“…In the municipality of Jagna, in the south-east of the island of Bohol, industrialization of the fishing fleet in the 1970's transformed a traditional coastal sailing harpoon-based fishery into a motorized offshore driftnet practice (Acebes and Tull, 2016). A monitoring program of this fishery revealed that over 2,000 individuals were landed per season (Authors, unpub data).…”
In light of the global decline of mobulid populations and the necessity for sustainable fisheries management, baseline data for population dynamics were collected from a targeted fishery in the Bohol Sea, Philippines. This study focused on life-history parameters and reproductive cycles of four mobulid rays (Mobula thurstoni, Mobula japanica, Mobula tarapacana, and Manta birostris), and re-estimated their intrinsic population growth rates. Size and reproductive data were collected from 1,509 specimens (30% of catch) landed in two fishing seasons in 2015 and 2016. Size-at-birth was reviewed, and analysis of the embryos and follicles did not show any clear seasonality in the reproductive cycle, but supported an interbreeding interval. Females of all species matured at a larger size than males, and exhibited a larger size-at-pregnancy than -at-maturity. This delay in reproduction resulted in population growth rates lower than the actual r max when based on size-at-pregnancy (r mat = r max = 0.016-0.055 year −1 and r preg = 0.008-0.044 year −1 ), and a population doubling time of 15.8-86.6 years. This study suggests that population growth rates previously reported were overestimated. In light of the Convention on International Trades of Endangered Species (CITES) and Convention on Migratory Species (CMS) assessments, while fisheries management should reflect the delayed maturation of these species and the slower population growth potential, at the current status of these population, the sustainability of any exploitation level seems unrealistic and strongly discouraged.
“…It is unclear why M. alfredi were not caught together with the other mobulids, but this trend may indicate habitat partitioning (Marshall et al, 2009;Deakos et al, 2011;Rambahiniarison et al, 2016), or local extirpation. Historical fishing grounds were closer to the coast than at present (Acebes and Tull, 2016), covering a habitat with different oceanographic characteristics (i.e., 0-500 m depth, slower currents in historical fishing grounds). Although M. alfredi is not as coastal as assumed in the past (Jaine et al, 2014), previous local population extinction could explain its current absence among the landed species.…”
Section: Mobulids In the Bohol Seamentioning
confidence: 97%
“…In the Bohol Sea, Philippines, direct fisheries have exploited mobulids for local consumption and gill rakers export for over a century (Fowler et al, 2002;Rayos et al, 2012;Acebes and Tull, 2016), and are now banned since April 2017 after the implementation of the CITES listing. In the municipality of Jagna, in the south-east of the island of Bohol, industrialization of the fishing fleet in the 1970's transformed a traditional coastal sailing harpoon-based fishery into a motorized offshore driftnet practice (Acebes and Tull, 2016).…”
Section: Introductionmentioning
confidence: 99%
“…In the municipality of Jagna, in the south-east of the island of Bohol, industrialization of the fishing fleet in the 1970's transformed a traditional coastal sailing harpoon-based fishery into a motorized offshore driftnet practice (Acebes and Tull, 2016). A monitoring program of this fishery revealed that over 2,000 individuals were landed per season (Authors, unpub data).…”
In light of the global decline of mobulid populations and the necessity for sustainable fisheries management, baseline data for population dynamics were collected from a targeted fishery in the Bohol Sea, Philippines. This study focused on life-history parameters and reproductive cycles of four mobulid rays (Mobula thurstoni, Mobula japanica, Mobula tarapacana, and Manta birostris), and re-estimated their intrinsic population growth rates. Size and reproductive data were collected from 1,509 specimens (30% of catch) landed in two fishing seasons in 2015 and 2016. Size-at-birth was reviewed, and analysis of the embryos and follicles did not show any clear seasonality in the reproductive cycle, but supported an interbreeding interval. Females of all species matured at a larger size than males, and exhibited a larger size-at-pregnancy than -at-maturity. This delay in reproduction resulted in population growth rates lower than the actual r max when based on size-at-pregnancy (r mat = r max = 0.016-0.055 year −1 and r preg = 0.008-0.044 year −1 ), and a population doubling time of 15.8-86.6 years. This study suggests that population growth rates previously reported were overestimated. In light of the Convention on International Trades of Endangered Species (CITES) and Convention on Migratory Species (CMS) assessments, while fisheries management should reflect the delayed maturation of these species and the slower population growth potential, at the current status of these population, the sustainability of any exploitation level seems unrealistic and strongly discouraged.
“…For a direct, short-term, assessment of diet, access to dead specimens is required, which can be challenging for rare or internationally protected species, such as mobulids. A targeted mobulid fishery operates out of Jagna, Bohol, in the Philippines from November to May (figure 1); [20,21], giving us the opportunity to study the short-term feeding ecology of landed species directly. Figure 1.Fishing locations in the Bohol Sea.…”
Mobulid rays have a conservative life history and are caught in direct fisheries and as by-catch. Their subsequent vulnerability to overexploitation has recently been recognized, but fisheries management can be ineffective if it ignores habitat and prey preferences and other trophic interactions of the target species. Here, we assessed the feeding ecology of four mobulids (Manta birostris, Mobula tarapacana, M. japanica, M. thurstoni) in the Bohol Sea, Philippines, using stomach contents analysis of fisheries specimens landed between November and May in 2013–2015. We show that the mobulids feed heavily on euphausiid krill while they are in the area for approximately six months of the year. We found almost no trophic separation among the mobulid species, with Euphausia diomedeae as the major prey item for all species, recorded in 81 of 89 total stomachs (91%). Mobula japanica and M. thurstoni almost exclusively had this krill in their stomach, while M. tarapacana had a squid and fish, and Ma. birostris had myctophid fishes and copepods in their stomachs in addition to E. diomedeae. This krill was larger than prey for other planktivorous elasmobranchs elsewhere and contributed a mean of 61 364 kcal per stomach (±105 032 kcal s.e., range = 0–631 167 kcal). Our results show that vertically migrating mesopelagic species can be an important food resource for large filter feeders living in tropical seas with oligotrophic surface waters. Given the conservative life history of mobulid rays, the identification of common foraging grounds that overlap with fishing activity could be used to inform future fishing effort.
“…The existing conservation measures in regard to manta rays are mainly regulatory and legislative, such as the listing of the two species, Mobula alfredi and Mobula birostris, as "Vulnerable" and "Endangered, " respectively, under IUCN; their inclusion in Appendix-II in the CITES and CMS treaties; and local protection (Marshall et al, 2011). However, additional fisheries are continually being established (Croll et al, 2016) and manta ray populations are declining (Lewis et al, 2015;O'Malley et al, 2017), suggesting that these measures fall short of effective management plans, mainly due to lack of enforcement and an absence of alternative livelihood sources for the fisherfolk (Acebes and Tull, 2016).…”
Identifying critical aggregation sites and behavioral patterns of imperiled species contributes to filling knowledge gaps essential for their conservation. Manta rays present a prominent example of such species, the populations of which are declining globally due to directed fishery, by-catch, and other anthropogenic stressors. Our goal was to explore manta ray aggregation sites in the Philippines in order to determine the factors governing the mantas' visits -a knowledge gap essential to understand manta ecology, facilitate ecosystem-based fishery management, and promote sustainable manta-based ecotourism. Diving surveys, environmental conditions assessment, and autonomous cameras were employed to study manta behavior and visit patterns to a cleaning station cluster on a commonly fished seamount, visited by both Mobula birostris and Mobula alfredi. Our findings reveal several environmental conditions (e.g., sea state, moon illumination, and flow) that serve as predictors of manta presence/absence at the site. We suggest that these conditions affect both the behavior of the manta's food (i.e., the spatial distribution of plankton) and the cleaning effectiveness of the cleaner wrasse, which consequently influence manta activity. The findings suggest a trade-off between cleaning and foraging: i.e., mantas tend to visit the cleaning stations when environmental conditions are less favorable for foraging but suitable for effective cleaning; while being absent from the cleaning stations when environmental conditions form plankton aggregations, ideal for efficient feeding. This study sheds light on manta behavior and habitat use on dynamic, small spatio-temporal scales (i.e., hundreds of meters to a few kilometers, hours to days). The acquired data may be applied in the planning of marine protected areas and in fishery management (e.g., to reduce the chances of manta bycatch by limiting fishing activities to periods of manta absence) as well as contribute to enhancing sustainable exploitation, such as ecotourism, by increasing the chances of diving encounters with manta rays.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
