Extremely low genetic variability within and among locations of the greenfish holothurian<i>Stichopus chloronotus</i>Brandt, 1835 in Okinawa, Japan

Soliman, Taha; Takama, Okuto; Fernández-Silva, Iria; Reimer, James Davis

doi:10.7717/peerj.2410

Cited by 9 publications

(4 citation statements)

References 40 publications

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“…2B). Due to recent commercial pressure and reported large drops in abundances of some echinoderms (e.g., annual Okinawa Prefecture harvest of Tripneustes gratilla sea urchin from >700 t in 1976 to <50 t in late 1990s (Kakuma, 2003), see also Soliman, Fernandez-Silva & Reimer (2016); Soliman et al (2016)), it is clear that more research is urgently needed in other sub-regions. Hughes, Bellwood & Connolly (2002) suggested nearly two decades ago that more work is needed on understudied small and cryptic coral reef taxa in understudied locations, and this is still true for the RYS.…”

Section: Discussionmentioning

confidence: 99%

Marine biodiversity research in the Ryukyu Islands, Japan: current status and trends

Reimer

Biondi

Lau

et al. 2019

PeerJ

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Marine biodiversity and derived ecosystem services are critical to the healthy functioning of marine ecosystems, and to human economic and societal well-being. Thus, an understanding of marine biodiversity in different ecosystems is necessary for their conservation and management. Coral reefs in particular are noted for their high levels of biodiversity, and among the world’s coral reefs, the subtropical Ryukyu Islands (RYS; also known as the Nansei Islands) in Japan have been shown to harbor very high levels of marine biodiversity. This study provides an overview of the state of marine biodiversity research in the RYS. First, we examined the amount of English language scientific literature in the Web of Science (WoS; 1995–2017) on six selected representative taxa spanning protists to vertebrates across six geographic sub-regions in the RYS. Our results show clear taxonomic and sub-region bias, with research on Pisces, Cnidaria, and Crustacea to be much more common than on Dinoflagellata, Echinodermata, and Mollusca. Such research was more commonly conducted in sub-regions with larger human populations (Okinawa, Yaeyama). Additional analyses with the Ocean Biogeographic Information System (OBIS) records show that within sub-regions, records are concentrated in areas directly around marine research stations and institutes (if present), further showing geographical bias within sub-regions. While not surprising, the results indicate a need to address ‘understudied’ taxa in ‘understudied sub-regions’ (Tokara, Miyako, Yakutane, Amami Oshima), particularly sub-regions away from marine research stations. Second, we compared the numbers of English language scientific papers on eight ecological topics for the RYS with numbers from selected major coral reef regions of the world; the Caribbean (CAR), Great Barrier Reef (GBR), and the Red Sea (RES). As expected, the numbers for all topics in the RYS were well below numbers from all other regions, yet within this disparity, research in the RYS on ‘marine protected areas’ and ‘herbivory’ was an order of magnitude lower than numbers in other regions. Additionally, while manuscript numbers on the RYS have increased from 1995 to 2016, the rate of increase (4.0 times) was seen to be lower than those in the CAR, RES, and GBR (4.6–8.4 times). Coral reefs in the RYS feature high levels of both endemism and anthropogenic threats, and subsequently they contain a concentration of some of the world’s most critically endangered marine species. To protect these threatened species and coral reef ecosystems, more data are needed to fill the research gaps identified in this study.

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Section: Discussionmentioning

confidence: 99%

Marine biodiversity research in the Ryukyu Islands, Japan: current status and trends

Reimer

Biondi

Lau

et al. 2019

PeerJ

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“…Furthermore, it has been shown that S. chloronotus is also overharvested in East Africa and the Pacific ( Pirog et al, 2019 ). As well, based on extremely low mitochondrial genetic diversity, it has been suggested this species has experienced high anthropogenic pressure around Okinawajima Island ( Soliman et al, 2016 ). In the present study, the low population density of S. chloronotus compared to previous studies (0.04 ind/m 2 maximum in current study; 0.09 ind/m 2 at Mauritius ( Lampe, 2013 ); 1.5–3.6 ind/m 2 at La Réunion ( Kohler, Gaudron & Conand, 2009 )) may also show such impacts.…”

Section: Discussionmentioning

confidence: 99%

Shallow epifaunal sea cucumber densities and their relationship with the benthic community in the Okinawa Islands

Hamamoto

Poliseno

Soliman

et al. 2022

PeerJ

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Sea cucumbers are important ecological engineers in marine ecosystems. However, the fishery demand of some species, especially large-epifaunal and commercially used (LEC) sea cucumbers, has risen drastically, resulting in serious depletion of local populations for many species. Despite this problem, basic ecological data on sea cucumbers, such as population densities and preferred habitats, are often still insufficient. Here, we report on the population densities of multiple LEC sea cucumber species, and their ambient benthic communities at eight sites around Okinawa Islands. Further, we discuss the correspondence between sea cucumber densities and the surrounding coral communities. Our results show two sites within national or quasi-national parks, Aka and Manza, where stricter rules have been placed on fisheries and land reclamation compared to other areas, had the highest and third highest sea cucumber population densities among sites, respectively. Holothuria atra was observed at all survey sites and made up the majority of sea cucumber populations at all sites except for Chatan and Sesoko, where Holothuria leucospilota and Stichopus chloronotus were most abundant, respectively. Regarding the relationships between benthic composition and LEC sea cucumber species, S. chloronotus was significantly correlated with dead corals, scleractinian corals, and coralline algae. As well, H. leucospilota had significant correlations with rubble. Although there were no significant correlations between any specific scleractinian coral genus and sea cucumber densities, S. chloronotus was marginally insignificant with Platygyra and Psammocora. Notably, medium- to highly valued species were sparse in our surveys, and most of them appeared at only one site. Additionally, at one site (Odo), only three LEC sea cucumber individuals were observed. Combining these facts with relatively low population densities around the Okinawa Islands compared to densities reported in previous research from the Indo-West Pacific Ocean region, we conclude that Okinawan LEC sea cucumber populations have been and are being impacted by high levels of direct (e.g., overexploitation, as well as coastal development) and indirect anthropogenic pressure (e.g., decreasing water quality). To address the current situation, repeated monitoring and more detailed investigations to reveal the drivers that determine LEC sea cucumber species aggregations and population densities are urgently needed, along with more robust management of remaining LEC sea cucumber populations.

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“…Other studies reported that genus Stichopus widely distribute across most of the tropical Indo-Pacific region, from the Western Indian Ocean to the Central Pacific, and from southern Japan to northern Australia. This genus can observe from shallow to deep waters from the intertidal zone to depths of 30 m on coral reef flats and slopes in dense numbers, of which greenfish sea cucumber S. chloronotus is an economically and ecologically important species [12,20]. In this survey, vertical distribution of sea cucumbers is different among species e.g.…”

Section: Oceanography and Fisheries Open Access Journalmentioning

confidence: 99%

Investigating Species Compositions of Sea Cucumbers in Nam Du Island, Kien Giang Province, Vietnam

Khanh¹

2020

OFOAJ

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Six field trips were conducted to assess the species composition and size structure of sea cucumbers at Nam Du Island, Kien Giang province, Vietnam from March to December 2018. Numerous sites covering different depths (1-30 m) and habitats (intertidal flats, sea grass beds, rocky beds, and coral reefs) were done during the night by walking and snorkeling diving for collecting sea cucumbers. A total of 389 harvested samples, 14 species were found from two families such as Holothuriidae (8 species) and Stichopodidae (6 species). The most dominant species found around the island was Holothuria leucospilota (32.13%) followed by Pearsonothuria graeffei (31.11%) and Stichopus variegatus (17.22%). Conversely, the high commercial species (H. fuscogilva, H. nobilis and H. scabra) occupied a negligible quantity (<1%) that indicated extreme reduction of natural stock of these species. The harvested species were found in the Islands at the depth from 2 to 30 m. The sizes of harvested sea cucumbers in term of length varied from 10 to 47 cm and their individual weights were between 45 and 1854 g.

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Extremely low genetic variability within and among locations of the greenfish holothurianStichopus chloronotusBrandt, 1835 in Okinawa, Japan

Cited by 9 publications

References 40 publications

Marine biodiversity research in the Ryukyu Islands, Japan: current status and trends

Marine biodiversity research in the Ryukyu Islands, Japan: current status and trends

Shallow epifaunal sea cucumber densities and their relationship with the benthic community in the Okinawa Islands

Investigating Species Compositions of Sea Cucumbers in Nam Du Island, Kien Giang Province, Vietnam

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