“…This niche overlap is supported by previous work on stomach content analyses in the short term and stable isotope analyses in the longer term . A further 5th species, the reef manta ray Manta alfredi, was recently confirmed from the area, but only found once over four monitoring seasons (Rambahiniarison et al, 2016). Manta alfredi were also caught in a nearby fishery ∼130 km from Jagna, off Dinagat Island in the Surigao Strait .…”
Section: Mobulids In the Bohol Seamentioning
confidence: 91%
“…Manta alfredi were also caught in a nearby fishery ∼130 km from Jagna, off Dinagat Island in the Surigao Strait . 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).…”
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.
“…This niche overlap is supported by previous work on stomach content analyses in the short term and stable isotope analyses in the longer term . A further 5th species, the reef manta ray Manta alfredi, was recently confirmed from the area, but only found once over four monitoring seasons (Rambahiniarison et al, 2016). Manta alfredi were also caught in a nearby fishery ∼130 km from Jagna, off Dinagat Island in the Surigao Strait .…”
Section: Mobulids In the Bohol Seamentioning
confidence: 91%
“…Manta alfredi were also caught in a nearby fishery ∼130 km from Jagna, off Dinagat Island in the Surigao Strait . 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).…”
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.
“…Few data are available from this region, though whale shark hunters once operated from Talisayan in Misamis Oriental and in Salay, where ∼100 individuals were landed per year in the 1990’s ( Alava et al, 2002 ), and where Eckert et al (2002) tagged two whale sharks in 1997. Both tagging sites are within the Bohol Sea, a rich ecosystem that reaches >2,000 m depth and hosts 19 species of cetaceans ( Ponzo et al, 2011 ), marine turtles ( Quimpo, 2013 ; Araujo et al, 2016 ), five species of mobulid rays ( Rambahiniarison et al, 2016 ), and in which whale shark movements have been confirmed through photo-ID ( Araujo et al, 2014 ; Araujo et al, 2017a ). (c: “TRNP”) Tubbataha Reefs Natural Park (TRNP) has been an offshore no-take marine protected area (MPA) since 1988 and a UNESCO World Heritage Site since 1993.…”
The whale shark Rhincodon typus was uplisted to ‘Endangered’ in the 2016 IUCN Red List due to >50% population decline, largely caused by continued exploitation in the Indo-Pacific. Though the Philippines protected the whale shark in 1998, concerns remain due to continued take in regional waters. In light of this, understanding the movements of whale sharks in the Philippines, one of the most important hotspots for the species, is vital. We tagged 17 juvenile whale sharks with towed SPOT5 tags from three general areas in the Sulu and Bohol Seas: Panaon Island in Southern Leyte, northern Mindanao, and Tubbataha Reefs Natural Park (TRNP). The sharks all remained in Philippine waters for the duration of tracking (6–126 days, mean 64). Individuals travelled 86–2,580 km (mean 887 km) at a mean horizontal speed of 15.5 ± 13.0 SD km day−1. Whale sharks tagged in Panaon Island and Mindanao remained close to shore but still spent significant time off the shelf (>200 m). Sharks tagged at TRNP spent most of their time offshore in the Sulu Sea. Three of twelve whale sharks tagged in the Bohol Sea moved through to the Sulu Sea, whilst two others moved east through the Surigao Strait to the eastern coast of Leyte. One individual tagged at TRNP moved to northern Palawan, and subsequently to the eastern coast of Mindanao in the Pacific Ocean. Based on inferred relationships with temperature histograms, whale sharks performed most deep dives (>200 m) during the night, in contrast to results from whale sharks elsewhere. While all sharks stayed in national waters, our results highlight the high mobility of juvenile whale sharks and demonstrate their connectivity across the Sulu and Bohol Seas, highlighting the importance of the area for this endangered species.
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.
