Article

The fate of the most threatened order of elasmobranchs: Shark-like batoids (Rhinopristiformes) in the Arabian Sea and adjacent waters

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  • Elasmo Project
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Abstract

Shark-like batoids (Rhinopristiformes) represent of some of the most threatened families of sharks and rays. In certain regions, they are a relatively important component of elasmobranch fisheries, commonly taken as by-catch in gillnets and longlines, but also increasingly targeted for their high value fins and meat. This demand, combined with intense fishing pressure, has resulted in global population declines as well as localized extinctions of many rhinopristoids. Yet, information on the life-history, ecology, and conservation status remains scarce for most species. From 2010-2012, data was opportunistically collected from thirteen rhinopristoid species, including four endemic to the Arabian Sea and adjacent waters, landed from fisheries in the United Arab Emirates or transported from Oman. Four taxa dominated and comprised 92% of total shark-like batoid landings by number, namely Rhynchobatus spp., the Halavi guitarfish (Glaucostegus halavi), bowmouth guitarfish (Rhina ancylostoma), and Bengal guitarfish (Rhinobatos annandalei). Details of the biological characteristics, including size composition and sex ratios, are presented for each species. While there remain identification challenges related to some unresolved taxonomic issues, with several likely undescribed species occurring in the region, the first regional checklist of rhinopristoids is provided. Evidence of significant declines in landings combined with increasing fishing effort over a short time period raises concern about the status and long-term persistence of many species. Increased research to understand the biology, ecology, diversity, and resilience to harvest by fisheries is critical to the effective management of these species and an urgent precautionary approach to their conservation is warranted.

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... There are no species-specific time-series data available for guitarfish species that can be used to estimate population reduction. This is due to a lack of species-specific reporting as well as taxonomic and identification issues (Jabado, 2018). Given the lack of reporting from artisanal fisheries and the large number of nations fishing in African waters, actual landings are likely to be much higher than reported. ...
... There are no species-specific time-series data available for this guitarfish species that can be used to estimate population reduction. This is due to a lack of species-specific reporting as well as taxonomic and identification issues (Jabado, 2018). There have been limited records of this species in the past decade. ...
... There are limited species-specific time-series data available for this guitarfish species that can be used to estimate population reduction. This is due to a lack of species-specific reporting as well as taxonomic and identification issues (Jabado, 2018). This species has a relatively large range, but it is also under intense fishing pressure and suffers from severe habitat degradation. ...
Technical Report
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CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) wasopened for signature in Washington DC on 3rd March 1973, and to date has 184 Parties from across the world. If CITES is to remain a credible instrument for conserving species affected by trade, the decisions of the Parties must be based on the best available scientific and technical information. Recognizing this, IUCN and TRAFFIC have undertaken technical reviews of the proposals to amend the CITES Appendices submitted to the Nineteenth Meeting of the Conference of the Parties to CITES (CoP19). The Analyses - as these technical reviews are known - aim to provide as objective an assessment as possible of each amendment proposal against the requirements of the Convention, as agreed by Parties and laid out in the listing criteria elaborated in Resolution Conf. 9.24 (Rev. CoP17) and other relevant Resolutions and Decisions. To ensure the Analyses are as accessible as possible to all Parties, we have created a bespoke webpage where the Analyses can be downloaded individually by proposal or in full (see https://citesanalyses.iucnredlist.org/).
... chimaeras), hereafter referred to as 'sharks and rays'are a marine group with elevated extinction risk: one quarter of the species are estimated to be threatened globally . This extinction risk assessment reveals that sawfishes, wedgefishes, and guitarfishes are amongst the most threatened families and are of global conservation concern Jabado, 2018;Moore, 2017). Recent advances in taxonomy and phylogenetics have resolved some of the complex relationships of these rays (Faria et al., 2013;, enabling a new assessment of their status. ...
... Sawfishes, wedgefishes, and giant guitarfishes all have 'white' fins that are amongst the best quality and highest value in the fin trade (Dent & Clarke, 2015;Hau, Abercrombie, Ho, & Shea, 2018;Moore, 2017;Suzuki, 2002). Domestically, the meat is also an important source of protein, linking the status of these species to livelihoods in developing tropical countries (Jabado, 2018;Moore, 2017;Moore, Séret, & Armstrong, 2019). Sawfishes, wedgefishes, and guitarfishes were previously common in soft-bottom habitats of shallow warm waters, but have been heavily exploited through exposure to intensive trawl and gillnet fisheries in these habitats (Jabado, 2018;Moore, 2017). ...
... Domestically, the meat is also an important source of protein, linking the status of these species to livelihoods in developing tropical countries (Jabado, 2018;Moore, 2017;Moore, Séret, & Armstrong, 2019). Sawfishes, wedgefishes, and guitarfishes were previously common in soft-bottom habitats of shallow warm waters, but have been heavily exploited through exposure to intensive trawl and gillnet fisheries in these habitats (Jabado, 2018;Moore, 2017). ...
Article
• The process of understanding the rapid global decline of sawfishes (Pristidae) has revealed great concern for their relatives, the wedgefishes (Rhinidae) and giant guitarfishes (Glaucostegidae), not least because all three families are targeted for their high‐value and internationally traded ‘white’ fins. • The objective of this study was to assess the extinction risk of all 10 wedgefishes and six giant guitarfishes by applying the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, and to summarize the latest understanding of their biogeography and habitat, life history, exploitation, use and trade, and population status. Three of the 10 wedgefish species had not been assessed previously for the IUCN Red List. • Wedgefishes and giant guitarfishes have overtaken sawfishes as the most imperilled marine fish families globally, with all but one of the 16 species facing an extremely high risk of extinction through a combination of traits: limited biological productivity; presence in shallow waters overlapping with some of the most intense and increasing coastal fisheries in the world; and overexploitation in target and by‐catch fisheries, driven by the need for animal protein and food security in coastal communities and the trade in meat and high‐value fins. • Two species with very restricted ranges, the clown wedgefish (Rhynchobatus cooki) of the Malay Archipelago and the false shark ray (Rhynchorhina mauritaniensis) of Mauritania, may be very close to extinction. • Only the eyebrow wedgefish (Rhynchobatus palpebratus) is not assessed as Critically Endangered, with it occurring primarily in Australia where fishing pressure is low and some management measures are in place. Australia represents a ‘lifeboat’ for the three wedgefish and one giant guitarfish species occurring there. • To conserve populations and permit recovery, a suite of measures will be required that will need to include species protection, spatial management, by‐catch mitigation, and harvest and international trade management, all of which will be dependent on effective enforcement.
... Increasing global pressure by fishing and trade on cartilaginous fish (Chondrichthyans), including sharks, rays, skates (Elasmobranchii) is pushing stocks close to critical limits (Duly et al., 2017). Multiple Chondrichthyan stocks worldwide have depleted (Haque et al., 2018;Jabado, 2018;Moore, 2017;Dulvy et al., 2000;De Oliveira et al., 2013;Sguotti et al., 2016;Jabado et al., 2018;Kyne et al., 2020). Recent studies have documented that these depletions are most acute for Rhinopristiformes rays (Yan et al., 2021;Moore, 2017;Kyne et al., 2020). ...
... Rhino rays add to regional economies through artisanal, commercial and industrial fishing and international trade on the fin, meat and skin (Stewart et al., 2010;Bonfil and Abdallah, 2004;Jabado, 2018;Moore, 2017;Dunlop et al., 2013;Haque et al., 2018). Thus, these species are a component of a much-complicated socio-economic complex (Moore, 2017). ...
... Unsustainable fisheries and international fin trade have fuelled population decline. Indo-West Pacific (Iran to Indonesia) has been reported as the centre of global rhino ray population declines (Kyne et al., 2020), with highly depleted stocks and localised extirpations reports Jabado, 2018;Moore, 2017;Tous et al., 1998). It is likely that high rates of exploitation and the growing global trade have resulted in the declines, with wedgefish and guitarfish considered as threatened as sawfish (Haque et al., 2018;Jabado, 2018;Moore, 2017;Kyne et al., 2020). ...
Article
Rhinopristioid rays are among the most globally threatened cartilaginous fishes, almost all of which are Critically Endangered. Fishery pressure and lack of knowledge, especially where these elasmobranch fish overlap their habitats off developing countries in the Indo-West Pacific, impede their biological conservation which in turns result in unnoticed population depletion. Rhino rays are an important component of the Bangladeshi artisanal fishery; however, an understanding of these fisheries and their trade is limited. Fishers and traders were interviewed between June 2018 and June 2019 in four areas of southeast Bangladesh to characterize rhino ray fishing, trade and fishers' perception of population trends. All interviewed fishers reported lifelong rhino ray catch in sizable numbers and noted a steep decline in the catch over time, especially for Rhynchobatus spp. Seven species were documented-not only targeted by un-baited longlines but also by-caught in gillnets and set-bag nets. Unregulated and undocumented catch fuelled by substantial international trade to Myanmar on high-quality skin, meat and fins; and national usages of meat, liver, cartilages and intestines. Between 9000 and 33000 kg (avg. 23000 kg) of rhino rays were bought annually by each trader during 2015-2018. Southcentral shallow-water char (sand island) areas are perceived as essential habitats, hence providing important fishing grounds. The predominant threats are overexploitation by unselective gear use, bottom trawling, target catch, international trade and source of protein and income. Compliance with international trade control treaties or the Bangladeshi law was low, with most fishers (78%) unaware of specific regulation regarding rhino rays. It is crucial to adopt precautionary principles to prevent further rhino ray population declines. We propose a combination of actions rooted in sustainability and inclusiveness in this regard; e.g. a) trade mitigation, monitoring and enforcement, b) need for sustainable fisheries management regimes, c) need for habitat protection; finally, d) the importance of fishers' inclusiveness in conservation decision making.
... Kyne et al. (2019) while describing the threat of extinction being faced by wedgefish and guitarfish also gave an account of their fisheries (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011) from Sindh and Balochistan, Pakistan. Some aspects of the fisheries of these species in Pakistan were also included in studies carried out by Jabado (2018Jabado ( , 2019, Jabado and Spaet (2017) and . Gore et al. (2019) in his recent work on the elasmobranch fisheries of Balochistan also covered some aspects of fisheries guitarfish and wedgefish in province of Balochistan. ...
... These include placing sharks, rays and guitafishes on CITES Appendices or on IUCN Red List (Dulvy et al., 2014;Jabado et al., 2018;Last et al., 2016). There has been a surge on the studies focused on fisheries of elasmobranch in the Arabian Sea and contiguous sea (Chen, 1996;Dent and Clarke, 2015;Dulvy et al.,2014;Haque et al., 2018;Henederson et al., 2004;Jabado, 2018Jabado, , 2019Jabado and Ebert, 2015;Jabado and Spaet, 2017;Jabado et al., 2014Jabado et al., , 2018Karnard et al., 2020;Kyne et al., 2019;Moore, 2017). Some of these studies specifically dealt with fisheries guitarfish and wedgefish (Jabado, 2018;2019;Jabado and Spaet, 2017;Kyne et al., 2019;Moore, 2017). ...
... There has been a surge on the studies focused on fisheries of elasmobranch in the Arabian Sea and contiguous sea (Chen, 1996;Dent and Clarke, 2015;Dulvy et al.,2014;Haque et al., 2018;Henederson et al., 2004;Jabado, 2018Jabado, , 2019Jabado and Ebert, 2015;Jabado and Spaet, 2017;Jabado et al., 2014Jabado et al., , 2018Karnard et al., 2020;Kyne et al., 2019;Moore, 2017). Some of these studies specifically dealt with fisheries guitarfish and wedgefish (Jabado, 2018;2019;Jabado and Spaet, 2017;Kyne et al., 2019;Moore, 2017). Jabado and Spaet (2017) Pakistan. ...
Article
Full-text available
Guitarfish and wedgefish are commercially exploited in Pakistan (Northern Arabian Sea) since long. It is estimated that their commercial landings ranged between 4,206 m. tons in 1981 to 403 metric tons in 2011. Analysis of the landing data from Karachi Fish Harbor (the largest fish landing center in Pakistan) revealed that seven species of guitarfish and wedgefish are landed (January 2019-February 2020 data). Granulated guitarfish (Glaucostegus granulatus) contributed about 61.69 % in total annual landings of this group followed by widenose guitarfish (G. obtusus) contributing about 23.29 % in total annual landings of guitarfish and wedgefish. Annandale's guitarfish (Rhinobatos annandalei) and bowmouth guitarfish (Rhina ancylostoma) contributed 7.32 and 5.97 % in total annual landings respectively. Spotted guitarfish (R. punctifer), Halavi ray (G. halavi), smoothnose wedgefish (Rhynchobatus laevis) and Salalah guitarfish (Acroteriobatus salalah) collectively contributed about 1.73 % in total annual landings. Smoothnose wedgefish (R. laevis) is rarest of all the members of Order Rhinopristiformes. G. granulatus, G. obtusus, R. ancylostoma, G. halavi and R. laevis are critically endangered according to IUCN Red List whereas A. salalah is near threatened and R. annandalei is data deficient. There are no aimed fisheries for guitarfish and wedgefish in Pakistan but these fishes are mainly caught as by-catch of bottom-set gillnetting and shrimp trawling. Some aspects of biology of these species are also presented in the paper.
... All the batoids, especially Rhinopristiformes are considered to be at high risk of extinction in certain parts of the world and in view of this, a proposal to include all of them in the CITES annex is in the process (Moore, 2017). The Bengal guitarfish, Rhinobatos annandalei Norman, 1926, currently has a distribution range from Sri Lanka, India, Pakistan and also possibly from the Gulf (Last et al., 2016;Jabado, 2018). It is classed in the IUCN red list threatened species as data deficient (DD) (Valenti, 2009). ...
... However, the average annual landings decreased to 1.8 t during -2016(CMFRI, 20132015;2016). Though forming a fishery component in its distribution range, knowledge of its life history is poor and limited to a few studies in the north-eastern Arabian Sea (Vossoughi and Vosoughi, 1999;Raje, 2006;Raje et al., 2012;Jabado, 2018). Further, most of these studies are restricted to either length frequency or length-weight relationships and do not elicit details regarding its reproductive biology or diet. ...
... Elasmobranch fisheries demand vigilant management strategies that support sustainable and continuous harvest, while ensuring that the resource is not overexploited and avoids adverse impact on the ecosystem and extinction risk (Moore et al., 2012;Jabado et al., 2017;Jabado, 2018;Jabado et al., 2018). Guitarfishes have been identified as being amongst the most vulnerable of the elasmobranch families, after sawfishes (Dulvy et al., 2014;Moore, 2017). ...
Article
Biological data for the little known Bengal guitarfish Rhinobatos annandalei Norman, 1926 (Rhinopristiformes: Rhinobatidae) are presented based on specimens collected from bycatch of commercial shrimp trawlers, gill netters and bag or dol netters operating in the Arabian Sea at depths of 2-70 m off the north-west coast of India. Five hundred ninety-three specimens measuring 30.0 to 95.0 cm total length (TL) and weighing between 64.0 to 3300 g total weight (TW) were collected for the study. The length-weight relationships (LWR) were significantly different between the sexes (p<0.001) and for the combined sexes was derived as TW= 0.000604 TL3.408256 (r2= 0.997). The co-efficients ‘a’, ‘b’ of the LWR were estimated as 0.000621, 3.410115 (r2= 0.999) for females and 0.000766, 3.333872 (r2= 0.999) for males. The length at maturity (TL50) for females and males was estimated to be 61.0 and 63.3 cm TL, respectively. In a single female, the number of embryos ranged from 2 to 11 and the size at birth was estimated between 25.0 to 30.0 cm TL. The overall sex ratio favoured females at the rate of 1.6:1. An analysis of the stomach contents (%IRI) revealed that R. annandalei mainly fed on Solenocera spp. (18.7% IRI), along with P. sculptilis (0.5% IRI), P. stylifera (0.4% IRI), Loligo spp. (0.4% IRI) and sciaenids (0.3% IRI). Since, the species is poorly studied and assessed as ‘Data Deficient’ in the IUCN red list criterion, it is anticipated that the biological results from the present study, will update information on the species thereby enabling more effective management decisions.
... Where Rhinopristiformes (sawfishes, wedgefishes, giant guitarfishes, and guitarfishes) have been targeted or exploited as incidental catch, severe declines, population depletions, and localized disappearances have occurred (e.g., Dulvy et al. 2016, Moore 2017, Jabado 2018. However, there are limited species-specific time-series data available for guitarfish species that can be used to estimate population reduction. ...
... However, there are limited species-specific time-series data available for guitarfish species that can be used to estimate population reduction. This is due to a lack of species-specific reporting as well as taxonomic and identification issues (Jabado 2018). ...
... Globally, guitarfishes are subject to intense fishing pressure that is unregulated across the majority of their distribution on their coastal and shelf habitats. Guitarfishes are captured in industrial, artisanal, and subsistence fisheries with multiple fishing gears, including gillnet, trawl, hook and line, trap, and seine net and are generally retained for their meat and fins (Moore 2017, Jabado 2018). There is a high level of fisheries resource use and increasing fishing pressure across the range of the Common Guitarfish, and demersal coastal fisheries resources have been severely depleted across the region.In the Mediterranean Sea, the Common Guitarfish is sometimes landed in fisheries as bycatch, however, it has largely disappeared from its former range in the northern regions of the Mediterranean. ...
... djiddensis 1; R. cf. djiddensis 2 and Rhynchobatus cooki Last, Kyne andCompagno, 2016 (Bineesh et al., 2014;Henderson et al., 2016;Last et al., 2016a,b;Jabado, 2018;Purushottama et al., 2018). ...
... This species has been targeted or exploited as incidental catch, primarily for fins and meat and is also a component of the bycatch in shrimp trawls in India and the 'white fins' are the main priced product. Few data are available on the population status; however, given its susceptibility to capture by multiple gear types, the known heavy fishing pressure from local and foreign vessels in parts of its range and its high value fins, it is highly likely that numbers significantly reduced and localised disappearance occurred (Tous et al., 1998;Dulvy et al., 2016;Moore, 2017;Jabado, 2018). Serious declines have occurred in populations of similar species for the same reasons, thus R. laevis is assessed as 'Critically Endangered' globally due to inferred population declines and continuing, unregulated high levels of exploitation (Kyne and Jabado, 2019). ...
... Guitarfishes form one of the most vulnerable groups in elasmobranchs (Dulvy et al., 2014;Moore, 2017;Jabado, 2018); their vulnerability compounded by the lack of detailed information on their reproduction, diet or stock status in the Indian Ocean. For this reason, the objective of this work was to focus on the reproduction, maturity and diet of R. laevis fished off north-west India, to update the information on life history of the species from the northern Indian Ocean. ...
Article
Full-text available
Large sized batoids particularly wedgefishes are highly vulnerable to fishing and yet very few studies have been publishedon their biology. The reproductive biology and feeding habit of Rhynchobatus laevis (Bloch and Schneider, 1801) from off the north-west coast of India, Arabian Sea is presented
... Giant guitarfish and wedgefish populations are most impacted by commercial extraction and finning (Figure 1; Davidson & Dulvy, 2017;Moore, 2017;Jabado, 2018). Demand for their characteristic dorsal and caudal fins means they are increasingly targeted by the booming international fin trade (Wainwright et al., 2018;Jabado, 2019). ...
... Apart from their fins, giant guitarfish and wedgefish meats in fresh and salted forms are consumed by communities along the coasts and in many developing countries. When sold fresh, these elasmobranchs can fetch a relatively high price of US$4 per kilogram (Choy CPP & Choo MY, 2020, unpublished data), and a whole wedgefish over 2 m in total length can be sold at prices as high as US$680 (Jabado, 2018) owing to its reputation as good quality meat (Moore, 2017). Together, artisanal and commercial fisheries put extreme pressure on harvested populations (Last, White & Pogonoski, 2008;Dulvy et al., 2014;Jabado et al., 2018a;D'Alberto et al., 2019), with declining catch rates in trawl surveys and reductions in landings reported at fishing ports across the Indo-West Pacific and Indian Ocean despite a substantial increase in fishing effort (Jabado et al., 2018b (Jabado, 2018). ...
... When sold fresh, these elasmobranchs can fetch a relatively high price of US$4 per kilogram (Choy CPP & Choo MY, 2020, unpublished data), and a whole wedgefish over 2 m in total length can be sold at prices as high as US$680 (Jabado, 2018) owing to its reputation as good quality meat (Moore, 2017). Together, artisanal and commercial fisheries put extreme pressure on harvested populations (Last, White & Pogonoski, 2008;Dulvy et al., 2014;Jabado et al., 2018a;D'Alberto et al., 2019), with declining catch rates in trawl surveys and reductions in landings reported at fishing ports across the Indo-West Pacific and Indian Ocean despite a substantial increase in fishing effort (Jabado et al., 2018b (Jabado, 2018). The remaining four species in the Glaucostegidae were also added to Appendix II to facilitate enforcement because of difficulties in distinguishing the confamilial species (CITES, 2019a). ...
Article
Full-text available
• Giant guitarfishes (Glaucostegidae) and wedgefishes (Rhinidae) are some of the most threatened marine taxa in the world, with 15 of the 16 known species exhibiting global population declines and categorized as Critically Endangered according to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. The recent inclusion of all species in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) necessitates more rigorous enforcement by regulatory authorities. • Challenges in regulating the trade of giant guitarfish and wedgefish products due to difficulties in visual identification of processed products and labelling issues impede enforcement. The aim of this study is to characterize the diversity and origins of associated traded products that were commercially available in Singapore, one of the world's top importers and re‐exporters of shark and ray products. • A total of 176 samples of elasmobranch products were obtained between June and December 2019 from fishery ports and various retailers in Singapore. By applying cytochrome c oxidase subunit I gene barcoding, 31 elasmobranch species were detected, with 55% of the species considered threatened (Critically Endangered, Endangered, or Vulnerable) based on the IUCN Red List and 35% of species listed in CITES Appendix II. Four species of giant guitarfishes and wedgefishes were commercially available to consumers in fresh forms of whole fish, fillet, and fin, as well as dried and cooked meats. • DNA barcoding has proven to be an effective tool for identifying elasmobranch products that are impossible to recognize visually and would aid enforcement of CITES trade regulations. This work underscores the urgent need to step up enforcement of marine wildlife regulations and draw public attention to the elasmobranch trade.
... The wedgefishes (family Rhinidae) and giant guitarfishes (family Glaucostegidae) (order Rhinopristiformes) are among the most threatened marine taxa globally [7,8]. According to the IUCN Red List of Threatened Species, 15 of the 16 assessed Rhinidae and Glaucostegidae species are considered Critically Endangered as a result of population declines driven by overfishing, as well as habitat loss and degradation, and one species (Rhynchobatus palpebratus) is Near Threatened as it occurs primarily in Australia where fishing pressure is low and managed [8,9]. ...
... As coastal human populations are increasing and fishing technologies and access to international markets are improving, fishing pressure has intensified across the range of both families [8,10,11]. They are caught as bycatch and targeted catch and there is evidence of overexploitation through a reduction in landings and biomass across their range [7,8,12]. ...
... Additional information on trade routes within the region are scarce, and insights into the scale of the trade in wedgefishes and giant guitarfishes across the wider Asian region are urgently needed. This is particularly important considering the lucrative nature and increasing global demand for wedgefish and giant guitarfish products such as fins, meat, snouts, and skin [7,8,16]. ...
Article
Wedgefishes (Rhinidae) and giant guitarfishes (Glaucostegidae) are amongst the most threatened marine taxa globally. Research was undertaken in Singapore, a globally significant trading hub for shark and ray products, between May 2019 (two months after they were proposed for listing on the Convention on International Trade in Endangered Species of Flora and Fauna (CITES)) and August 2019 (three months before listings entered into force). The study documents the composition of imports and landings, estimates the scale of the trade, describes the supply chain, and analyzes completeness of product labels through surveys in fishery ports and retail markets as well as informal interviews with traders. Of 590 individuals recorded at fishery ports, 215 from six species could be identified to the species-level. Rhynchobatus australiae was the most commonly encountered wedgefish species (66%) while only one species of giant guitarfish (Glaucostegus typus) was recorded. Individuals were primarily claimed to be imported from Indonesia and Malaysia. The high value of wedgefish fins was evident as a large proportion of individuals without fins (66%) were recorded. Businesses in Singapore were utilizing by-products of the fin trade which appeared to have a distinct supply chain. Traders noted declining supplies of wedgefishes and dried shark fins in recent years. Shark and ray products notably lacked information on species and country of origin on their labels. Findings here provide baseline data for determining the effectiveness of new trade controls and suggest that a multi-pronged approach with trade monitoring, additional traceability and labeling requirements, and enhanced fisheries management would conserve globally declining, wild populations.
... Rhino rays are increasingly targeted or retained as incidental catch in many fisheries and have thus become an essential component of landings worldwide for their value rather than their volume [83]. Their meat is mainly consumed locally, while their "white" fins are considered the highest quality and, thus, the most valuable of shark fins ( [37,74,53]). Guitarfishes are susceptible to capture in various fishing gears, including gillnets, longlines, and demersal trawls [6,31,64,65,66]. The high demand for their products, susceptibility to being caught by various fishing gears, and intense fishing pressure are all critical drivers of population decline globally [50,37,85]. ...
... Guitarfishes are susceptible to capture in various fishing gears, including gillnets, longlines, and demersal trawls [6,31,64,65,66]. The high demand for their products, susceptibility to being caught by various fishing gears, and intense fishing pressure are all critical drivers of population decline globally [50,37,85]. ...
... Male-dominated sex ratios were documented for Rhinobatos albomaculatus and R. irvinei, which may indicate sexual segregation; a phenomenon which is relatively common in elasmobranchs [75]. Similarly, sexual segregation has been reported for G. cemiculus and R. rhinobatos in The Gambia (Moore et al., [53]) and some species of rhino rays in the Arabian Sea and adjacent waters [37]. ...
Article
Rhino rays, such as guitarfishes, are increasingly targeted or retained as incidental catch and have become an economically important component in fisheries worldwide. Despite their importance, information about the catch and socioeconomics of these fisheries are virtually non-existent in West Africa. We address a significant knowledge gap about the characteristics and drivers of guitarfish fisheries in four key ray-fishing communities in the Western and Central Regions in Ghana. We conducted landing and market surveys of guitarfishes over 80 days from November 2020 to August 2021. We also interviewed 51 fishers actively involved in the guitarfish fishery across the four communities during this period using semi-structured interviews. The findings confirm the likely disappearance of sawfishes Pristis spp., as most fishers have not captured any in their lifetime. We also confirm no known catches of the African wedgefish Rhynchobatus luebberti. Our surveys documented 537 individuals from four guitarfish species across the various landing and market sites. The spineback guitarfish (Rhinobatos irvinei) was the most frequently landed species comprising 71 % (n = 383) of all guitarfishes, with 57 % of the specimens not yet sexually mature. Most fishers (71 %) stated that catches of the two larger guitarfishes (blackchin guitarfish Glaucostegus cemiculus and common guitarfish Rhinobatos rhinobatos) have declined by 80–90 % based on their recollection. At the same time, over half (59 %) of the fishers indicated that the catches of the smaller guitarfishes (spineback guitarfish and whitespotted guitarfish Rhinobatos albomaculatus) have declined by 40–60 %. The main drivers for the catch or retention of guitarfishes were for both international trade of their fins, and meat which are both traded locally (45 % of 51 fishers) and used as a source of food for local consumption (37 %). While we know high economic value drives the catch and trade of giant guitarfishes and wedgefishes, we show that this trade extends to the other guitarfish species. The interviews and contemporary pattern of catches are consistent with a serial depletion of rhino rays from the largest, most valuable species to the remaining smaller-bodied, less valuable guitarfishes. We recommend the development of national regulations for their protection complemented by education programs to ensure that fishers are aware of the threatened status of guitarfishes.
... Mobula kuhlii (Müller & Henle 1841) -Longhorned mobula Status in Persian Gulf: First record from Persian Gulf by ; previously reported by as Mobula diabolus (non Shaw 1804), Al-Hassan & Al-Badri (1986) as Mobula diabolus (non Shaw 1804), as Mobula dialobus (non Shaw 1804), Hussain et al. (1988) as Mobula diabolus (non Shaw 1804), as Mobula diabolus (non Shaw 1804), Moore et al. (2012a) as Mobula cf. eregoodootenkee and Jabado & Ebert (2015) as (1999) as Rhinobatos granulatus, Bishop (2003), Moore et al. (2012a) as Rhinobatos granulatus, Séret et al. (2016b) and Jabado (2018). Distribution: Northern Indian Ocean: Persian Gulf and Gulf of Oman east to Myanmar. ...
... Glaucostegus halavi ( Fabricius [ex Forsskål] Jabado (2018). Distribution: Northern Indian Ocean: Persian Gulf and Gulf of Oman east to Bay of Bengal (India). ...
Article
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This checklist aims to reviews and summarize the results of the systematic researches on the Persian Gulf ichthyofauna that has been carried out for more than 200 years. Since the work of C. Niebuhr, a Danish biologist in the 18th century, the number of valid species has increased significantly and the systematic status of many of the species has changed, and reorganization and updating of the published information has become essential. Here we take the opportunity to provide a new and updated checklist of fishes of Persian Gulf based on literature and taxon occurrence data obtained from natural history and new fish collections. The total confirmed fish species of Persian Gulf comprise 744 species, 131 families, 445 genera and 27 orders. In the class Chondrichthyes, the most diverse family is Charcharhinidae with 23 species (41.89%), followed by Dasyatidae with 15 species (31.08%). Within the class Actinopterygii, Gobiidae with 65 species (9.70%), Carangidae with 45 species (6.27%), Serranidae with 25 species (3.73%), Apogonidae with 25 species (3.73%), Lutjanidae with 23 species (3.43%) and Blenniidae with 23 species (3.43%) are the most diverse families in the Persian Gulf.
... In this paper, "sharks" is used to refer collectively to Chondrichthyan species -that is, sharks, skates, rays, and chimeras. Policymakers and resource managers encounter many compounding barriers in attempting to conserve shark populations, spanning across aspects from ecological and biological to institutional, economical, and sociological (Chin et al., 2010;Bornatowski et al., 2014;Dulvy et al., 2017;Jabado, 2018). Although some "bright spots" of shark fishery management have emerged , many populations are at risk of extinction due to historical over-exploitation, and a life-history pattern which lends to relatively slow recovery (e.g., larger sharks live relatively long, and reproduce small litters on a several-yearly basis) (Compagno, 1990;Field et al., 2010). ...
... However, the value of this partnership may go unacknowledged by fishery managers, presenting an untapped resource for gathering ecological data, while fostering stewardship through acknowledging the expertise of fishers. In developing nations, researchers associated with academic institutions are gathering experiential knowledge such as shark abundance, size trends, and market values through questionnaires, interviews, or by employing community members as data collectors (Jabado et al., 2015, Jabado, 2018Jaiteh et al., 2016a;Humber et al., 2017). These findings are shared with the academic community and others with access to scientific journals, however, pathways on how to use this in management are not explicit. ...
Presentation
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Sharks occupy unique roles in human society: objects of conservation campaigns, fishery and tourism resources, maligned predators inciting fear in beach-goers, and subjects of inquisitive scientists. There are more than 1250 species of sharks and their relatives, which have persisted on Earth in some evolutionary form for over 420 million years and now occupy countless environments - from arctic waters and tropical coral reefs, to deep seabeds and inland rivers. Sharks range in size from 20 centimeters (the dwarf lanternshark) to 20 meters (the whale shark), performing an array of functions in their natural habitats and in human society. For conservation purposes, sharks have generally been framed as having either intrinsic or instrumental value, that is value simply by merit of their existence or value for the sake of human use. This presentation will examine them in terms of relational values - that is, human values derived from a relationship with sharks, such as self- or community-identity, moral obligation to conserve non-human species, notions of well-being, and stewardship. We propose that efforts to rebuild or sustain shark populations through regulating human activities are more likely to succeed through assessing and considering relational values of all stakeholders, and mediating conflicting value frameworks (e.g., fishers versus environmentalists). We also discuss how relational values through sharks have manifested in the scientific community, fishers, indigenous groups, tourists, and the public, the unique roles held by each in ‘valuing’ sharks, and how policies targeting these groups’ behavior are well suited to include relational value assessments.
... The high-quality meat is consumed by many coastal 276 communities in tropical countries and it is also dried, salted, and consumed locally or traded 277 internationally (e.g. Moore, 2017;Jabado, 2018). Large whole wedgefishes (>200 cm total length; TL) 278 have been traded for a high value of up to US$680 each (e.g. ...
... Large whole wedgefishes (>200 cm total length; TL) 278 have been traded for a high value of up to US$680 each (e.g. Jabado, 2018). Prices for the highly-279 . ...
Preprint
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Shark-like rays (Order Rhinopristiformes) are among the most threatened families of marine fish. Yet little is known about their populations, as these rays are normally taken as opportunistic catch in fisheries targeting other species and are thus poorly reported. One exception is the Indonesian tangle net fishery, which targets shark-like rays. Market surveys of Muara Angke landing site in Jakarta, north-western Java (including one frozen shipment from Benoa Harbour, Bali), were conducted between 2001 and 2005, and recorded landed catch for this fishery. Recent catch data from Indonesian Capture Fisheries (2017 – 2018) were also examined to provide contemporary information about landed catch. 1,559 elasmobranchs (sharks and rays) were recorded, comprised of 24 species of rays and nine species of sharks. The most abundant species landed were the pink whipray Pateobatis fai and the bottlenose wedgefish Rhynchobatus australiae , the latter being the main target species. Catch composition varied based on differences in species catchability and may also be indicative of localized declines. The fishery was highly selective for larger sized individuals, however smaller size classes of target species were also caught in other Indonesian fisheries resulting in fishing pressure across all age classes. Evidence of substantial declines in global landings of wedgefish species, and the observed shift in catch composition in the Indonesian tangle net fishery, increases concerns about the status of shark-like rays and stingrays in Indonesia.
... The high-quality meat is consumed by many coastal 276 communities in tropical countries and it is also dried, salted, and consumed locally or traded 277 internationally (e.g. Moore, 2017;Jabado, 2018). Large whole wedgefishes (>200 cm total length; TL) 278 have been traded for a high value of up to US$680 each (e.g. ...
... Large whole wedgefishes (>200 cm total length; TL) 278 have been traded for a high value of up to US$680 each (e.g. Jabado, 2018). Prices for the highly-279 . ...
Preprint
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The process of understanding the rapid global decline of sawfishes (Pristidae) has revealed great concern for their relatives, the wedgefishes (Rhinidae) and giant guitarfishes (Glaucostegidae), not least because all three families are targeted for their high-value and internationally-traded ‘white’ fins. The objective of this study was to assess the extinction risk of all 10 wedgefishes and 6 giant guitarfishes by applying the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, and to summarise their biogeography and habitat, life history, exploitation, use and trade, and population status. Wedgefishes and giant guitarfishes have overtaken sawfishes as the most imperilled marine fish families globally, with all but one of the 16 species facing an extremely high risk of extinction due to a combination of traits – limited biological productivity, presence in shallow waters overlapping with some of the most intense and increasing coastal fisheries in the world, and over-exploitation in target and bycatch fisheries driven by the need for animal protein and food security in coastal communities and trade in meat and high-value fins. Two species with very restricted ranges, the Clown Wedgefish ( Rhynchobatus cooki ) of the Indo-Malay Archipelago and the False Shark Ray ( Rhynchorhina mauritaniensis ) of Mauritania may be very close to extinction. Only the Eyebrow Wedgefish ( Rhynchobatus palpebratus ) is not assessed as Critically Endangered, due to it occurring primarily in Australia where fishing pressure is low, and some management measures are in place. Australia represents a ‘lifeboat’ for the three wedgefish and one giant guitarfish species occurring there. To conserve populations and permit recovery, a suite of measures will be required which will need to include species protection, spatial management, bycatch mitigation, and harvest and international trade management, all of which will be dependent on effective enforcement.
... In this paper, "sharks" is used to refer collectively to Chondrichthyan species -that is, sharks, skates, rays, and chimeras. Policymakers and resource managers encounter many compounding barriers in attempting to conserve shark populations, spanning across aspects from ecological and biological to institutional, economical, and sociological (Chin et al., 2010;Bornatowski et al., 2014;Dulvy et al., 2017;Jabado, 2018). Although some "bright spots" of shark fishery management have emerged , many populations are at risk of extinction due to historical over-exploitation, and a life-history pattern which lends to relatively slow recovery (e.g., larger sharks live relatively long, and reproduce small litters on a several-yearly basis) (Compagno, 1990;Field et al., 2010). ...
... However, the value of this partnership may go unacknowledged by fishery managers, presenting an untapped resource for gathering ecological data, while fostering stewardship through acknowledging the expertise of fishers. In developing nations, researchers associated with academic institutions are gathering experiential knowledge such as shark abundance, size trends, and market values through questionnaires, interviews, or by employing community members as data collectors (Jabado et al., 2015, Jabado, 2018Jaiteh et al., 2016a;Humber et al., 2017). These findings are shared with the academic community and others with access to scientific journals, however, pathways on how to use this in management are not explicit. ...
Article
Full-text available
Relational values (RV) are values that arise from a relationship with nature, encompassing a sense of place, feelings of well-being (mental and physical health), and cultural, community, or personal identities. With sharks, such values are formed by diverse groups that interact with these animals and their ecosystems, either physically or virtually, whether a scientist, student, fisher, or media-viewer. Further, these user groups may overlap or come into conflict over management plans, media portrayals of sharks, and their conservation status. Although scientists have not explicitly aimed to assess RV through sharks, qualitative studies of shark fishers, tourism operators, tourists, and the public, as well as historical and archeological accounts, can be interpreted through an analytical lens to reveal values which can also be defined as relational. To this end, this review considers studies capturing RV alongside those of economic value (increasingly, the value of a shark is appraised by their financial value in shark tourism) and the social and cultural roles of sharks. Based on these studies and the broader RV literature, we then outline a workflow for how RV can be leveraged in scientific inquiry, equitable resource management, and education. We conclude that via collaborative assessments of RV, with implicit inclusion of multiple values of sharks and by acknowledging their importance to all parties involved in user conflicts, the RV framework can lead to a constructive dialog on polarizing conservation and management issues. By illuminating shared values, and/or revealing dichotomies of values ascribed toward certain areas or objects, this framework can provide inroads to mediation, seeking to conserve or even restore relationships with nature, and their derived values as much as is possible. This approach can yield unexpected knowledge, solutions, and compromises in an increasingly complex conservation landscape.
... Order Rhinopristiformes (including wedgefish) is arguably the most threatened elasmobranch globally (Dulvy et al., 2014;Jabado, 2018). This group is claimed to be experiencing global declines due to overexploitation (Jabado, 2018;D'Alberto et al., 2019). ...
... Order Rhinopristiformes (including wedgefish) is arguably the most threatened elasmobranch globally (Dulvy et al., 2014;Jabado, 2018). This group is claimed to be experiencing global declines due to overexploitation (Jabado, 2018;D'Alberto et al., 2019). Moore (2017) noted local extinctions had been reported for some species of guitarfish (probably including wedgefish). ...
Article
Wedgefish (family Rhinidae) is a group of elasmobranchs that experience a global threat due to its highly valued fins. Similar condition happens to most species of wedgefish inhabiting Indonesian waters where fishing activities are intense without sufficient management controls and lack of supporting studies on their sustainabilities. In order to get a picture of wedgefish populations in Indonesia, the current study employing demographic analysis was performed to know the population status of two wedgefish species (Rhynchobatus australiae and Rhina ancylostoma) from western Indonesian waters (including the Java Sea, Karimata and southern Makassar Straits). Age-based matrix models were used involving two scenarios of populations with and without fishing. Monte carlo simulation was applied to incorporate uncertainties in life�history parameters. The results show contrasting productivities for R. australiae and R. ancylostoma. R. aus�traliae is sufficiently productive, indicated by high population growth rates in both with and without fishing scenarios. In contrast, the population of R. ancylostoma grows positively only in the unfished scenario, but the growth is negative in the with-fishing scenario. This finding indicates that the current level of exploitation caused the depletion in the population of R. ancylostoma. The current level of fishing can be maintained for R. australiae to give optimum benefits to fishery communities, while for R. ancylostoma, substantial reduction in fishing is required. Protection of young fish (juveniles up to age at first reproduction) is recommended in both fish since population growths are very sensitive to the changes in these stages.
... More recently, the w e d g e f i s h e s ( R h i n i d a e ) a n d g i a n t g u i t a r f i s h e s (Glaucostegidae) have come into the public conscious as 15 of 16 species were assessed as being Endangered or Critically Endangered based on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species categories (Kyne et al. 2020). While steps have been taken to address concerns over these better known rhinopristiform batoids, the small-bodied guitarfishes (Rhinobatidae) have mostly been overlooked even though they share the same life history and habitat characteristics, and are subject to intense fishing pressure and habitat degradation (Moore 2017;Jabado 2018;Jabado et al. 2018). Further compounding conservation and fisheries management efforts have been lack of taxonomic clarity and speciesspecific identification. ...
... nov. presently appears to be restricted to the waters surrounding Socotra Islands and may be subject to intense traditional fisheries (Moore 2017;Jabado 2018;Jabado et al. 2018). Improvement for the situation of the two guitarfish species occurring off Madagascar might be achieved through the national plan of action for sharks and rays in Madagascar (Plan national de gestion et de conservation des requins et des raies à Madagascar, PNGCRR) (Anonymous 2019a), associated to an implementation plan for the period 2019-2023 (Anonymous 2019b). ...
Article
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Recent sampling efforts and examinations of museum material provided evidence for a complex of species within Acroteriobatus leucospilus (Norman, 1926). The present manuscript contains a redescription of A. leucospilus involving the syntypes and additional material, as well as formal descriptions of two new species of Acroteriobatus Giltay, 1928. All specimens of both new species were found in the western Indian Ocean. Individuals of the first new species, hereafter referred to as Acroteriobatus andysabini sp. nov., were identified originating from Madagascar, and specimens of the second new species, hereafter referred to as Acroteriobatus stehmanni sp. nov., were only found off Socotra Islands at the junction between the Gulf of Aden and the Arabian Sea. Both new species appear to be endemic to the respective region and allopatric to A. leucospilus and occur in coastal waters to at least 80 m and 43 m depth, respectively. They differ from A. leucospilus in a number of characteristics including the maximum size and coloration in fresh. Acroteriobatus andysabini sp. nov. is a large species growing to more than 100 cm total length (TL) and with elongated bluish-gray spots on snout giving “stripe-nosed” appearance; numerous small bluish-gray spots on pectoral, pelvic, dorsal, and caudal fins; brown spots on trunk and fin bases; lateral tail folds striped orange and white; and ventral surface largely white but with a V-shape pattern of faint to dark speckled black spots on snout tip. Acroteriobatus stehmanni sp. nov. is a small species growing to ~62 cm TL and with sparse patterning with small bluish-gray circular spots confined to snout tip, posterior pectoral-fin margins, a pair on midbody, and few on posterior pelvic-fin margins, rather indistinct small to larger dark brown spots, and lateral tail folds and ventral surface white. Acroteriobatus leucospilus is a medium-sized species growing to ~96 cm TL and with patterning similar to A. andysabini sp. nov. but ventral surface uniformly white and lateral tail folds white or striped blue and brown. Taxonomical differences include nasal lamellae counts (42–48 in A. andysabini sp. nov. vs. 43–48 in A. stehmanni sp. nov. vs. 37–41 in A. leucospilus ), snout angle (76–85° vs. 71–77° vs. 68–81°), and dorsal head length (24.2–33.5% vs. 17.2–22.8% TL vs. 24.0–29.2% TL). A key to the species of Acroteriobatus is given for the first time.
... Worldwide, shark stocks are severely under pressure due to overexploited and unregulated fisheries [1,2]. Although sharks are targeted in fisheries operating in the Arabian/Persian Gulf (hereafter the Gulf), information on regulatory and law enactment remains deficient [3][4][5]. It appears that the limited capacity of regulatory officers and the fact that action-plans are implemented voluntarily without the legal basis of continued enforcement. ...
... Although established, in order to deliver successful protection outcomes, these efforts must translate to implementing legislation and management actions at local, regional, and international levels-which can be adopted at scale. Despite the evidence of increasing concern for the conservation of sharks among scientists and environmental conservation advocates in the Arabian Seas Region, it appears that the lack of adequate law enforcement impedes fisheries management and current conservation efforts [4,5,31]. While the focal point of the fin trade is still considered to be Asia, the U.A.E.'s ports of entry are central to the global shark trade, making the latest Decree an important milestone in regional shark conservation. ...
Article
Full-text available
Challenges that relate to shark conservation may well be a combination of the intersection of people's livelihoods and the ineffectiveness of management strategies. Given the current protection initiatives as well as the implementation of tighter laws restricting hunting and trade, shark conservation is still recognized as a major environmental challenge. The United Arab Emirates (U.A.E.) is used as an export hub and is one of the primary exporters of shark fins to Hong Kong, with a large proportion of fins traded to be from species at high risk of global extinction. The present-day management of shark fisheries also shows shortcomings concerning lawfulness, specifically those relating to regulatory compliance, fishing techniques, and control of finning occurrences. These concerns are not unique to the U.A.E. but emphasize the fact that there are far-reaching problems related to shark conservation. Even in a milieu of strengthened conservation measures and revised legislature, existing information on the effectiveness of a shark finning ban may still be misleading when viewed in the light of over-exploitation and global species abundance. It is therefore important that proper management must be implemented at the inception of shark fisheries. For the U.A.E., this has not always been the case. Instead, the trend was one of limited control and lack of compliance, unfortunately, resulting in a rapid decline in shark abundance, to the point where sharks struggle to recover. This paper focuses on the importance of the species, reviews the current monitoring framework, and seeks to enhance shark protection.
... Compared to the Red Sea where elasmobranchs have been already assessed as overexploited (Sheppard et al., 2010;Qurban et al., 2012;Naser, 2014;Spaet and Berumen, 2015), knowledge on the status of elasmobranchs in the Gulf are still limited and patchy. An interview-based survey conducted in the United Arab Emirates (UAE) showed that sharks have been overexploited in the southern Gulf (Jabado et al., 2015a) and that elasmobranchs are facing the risk of regional extinction in the Gulf (Jabado et al., 2017a;Moore, 2017;Jabado, 2018). The present work was conducted with this concern, and it aims at (i) characterizing the elasmobranch community in the Saudi waters of the Gulf based on fishery-independent and dependent surveys, (ii) reviewing the conservation status of these taxa, and (iii) making recommendations for strengthening management plans for these natural resources. ...
... The total number of individuals and total weight of all elasmobranchs were recorded species-wise after photographing and identification. Specimens collected were identified following the identification keys of Carpenter et al. (1997), Ebert et al. (2013), Almojil et al. (2015), Jabado andEbert (2015), andLast et al. (2016). ...
Article
In spite of the ecological services provided by elasmobranchs, their diversity and populations are significantly declining even before appropriate assessments are conducted. This paper presents information on elasmobranch diversity in the Saudi waters of the Arabian Gulf based on fishery-independent and dependent surveys. A total of 369 individual sharks and batoids were collected from 119 out of 228 trawl stations surveyed between 2013 and 2016. Gymnura poecilura and Carcharhinus dussumieri were the most dominant batoid and shark species, respectively. The catch per unit area indicated the waters around Jana Island as a hotspot of elasmobranchs. A total of 135 surveys at the landing sites and fish markets from 2016 to 2020 showed that 88% of elasmobranchs (out of 4,055 individuals recorded) were caught by gill nets. Sharks were the most abundant (> 80 %) with three dominant species: Carcharhinus sorrah, C. humani, and C. limbatus. In total, 47 species of elasmobranchs (24 sharks and 23 batoids) belonging to 16 families and 5 orders were recorded from a possible 58 total species predicted by species richness extrapolators (Chao 1). High values of Margalef richness (> 2) and Shannon-Wiener index (3-4) suggested rich diversity of elasmobranchs in the study area with homogeneous distribution over the years and seasons as shown by cluster and similarity profile analysis. Of the 47 species recorded, six species were Critically Endangered regionally, six Endangered, and seven species Vulnerable according to the IUCN Red List of Threatened Species, necessitating proper management and conservation measures.
... These levels of declines are not species-specific but are informative for understanding the broader levels of decline in batoids in the region. Additionally, elsewhere where rhinopristoid rays (sawfishes [Pristidae], wedgefishes [Rhinidae], giant guitarfishes [Glaucostegidae], and guitarfishes [Rhinobatidae]) have been targeted or exploited as incidental catch, severe declines, population depletions, and localized disappearances have occurred (e.g., Tous et al. 1998, Dulvy et al. 2016, Moore 2017, Jabado 2018, Kyne et al. 2020. Historical accounts and contemporary datasets show: (1) a 93% decline in 'Rhinobathidae' (which probably equals guitarfishes generally) catch rate in the Gulf of Thailand from peak catches in 1968 to 1972 (Ritragsa 1976, Pauly 1979, Kyne et al. 2020); (2) the collapse of Indonesian targeted wedgefish fisheries (Chen 1996, Suzuki 2002, Kyne et al. 2020; (3) the depletion of rays (which can be used to infer declines in guitarfishes) in the Java Sea (Blaber et al. 2009) (recent trawl surveys in the Java Sea and North Natuna Sea recorded only three Rhynchobatus; Tirtadanu et al. 2018, Yusup et al. 2018); (4) declines in landings from Iran, Pakistan, and Indonesia, which are the equivalent of 81-99% population reduction over the last three generation lengths (30 years) (DGCF 2015, 2017, FAO 2018, Kyne and Ebert 2019, Kyne et al. 2020; and, (5) significant declines in landings of 'guitarfishes' in Tamil Nadu (86% decline for a 5-year period) and catch rates of rays (which is representative of declines in demersal batoids) in Maharashtra, India (63% decline for a 15-year period) (Mohanraj et al. 2009, Raje and Zacharia 2009, Kyne and Ebert 2019, Kyne et al. 2020. ...
... It is captured in industrial, artisanal, and subsistence fisheries with multiple fishing gears, including trawl, gillnet, set net, and longline and is retained for the meat and fins. Across the broader Indo-Pacific region, guitarfish species are often targeted and are heavily exploited and increasing fishing effort has put significant pressure on all guitarfish species in the Indo-West Pacific (Moore 2017, Jabado 2018, Kyne et al. 2020. In Taiwan, fishing is occurring in inshore areas in a potential nursery area at Penghu Island where most of the Brown Guitarfish landings are of gravid females with near-term embryos, which is of concern (P. ...
... Nursery and breeding grounds are particularly at risk. Coastal development is a major threats to Galucostegidae ( Jabado et al. 2018 Biological Diversity in the Mediterranean of the Barcelona Convention in 2012, hence landings are illegal in signatory states. K-selected life history, large size, high fin price and a distribution mostly encompassing countries with unregulated or unsustainable fisheries make Glaucostegidae one of the elasmobranch taxa with the highest risk of extinction (Moore et al, 2017). ...
Technical Report
Full-text available
Scientific opinion of the Norwegian Scientific Committee for Food and Environment (VKM)
... The implementation of effective management measures is urgently required in order to ensure the conservation of Gulf elasmobranch stocks (Jabado and Spaet, 2017). Some taxa, such as the sawfishes (Pristidae), were once common in the region but are now functionally extinct (Moore, 2015), while landings of others continue to decline despite increasing fishing effort (Jabado, 2018). Numerous matters need to be addressed in order to pave the way for meaningful management measures in the region (Moore, 2012a), but as mentioned in the introduction to this article, the fundamental requirement in species-specific data collection is that species are correctly identified. ...
Article
Species-specific biological data are commonly combined with fishery operational data to model exploited stocks and determine appropriate levels of exploitation. However, this approach to fishery management is predicated on the ability of fishery data collectors to correctly identify exploited spe- cies. Sharks and other elasmobranch fishes (Elasmobranchii) can be particularly difficult to identify in the field, due to the close physical similarity to other species and/or a lack of taxonomic resolution in some lineages. This paper provides an overview of the difficulties surrounding the field identifica- tion of a number of elasmobranch species found in the Arabian/Persian Gulf, where they are heavily exploited and in urgent need of careful management.
... Similarly, although there is currently no limit on the commercial catches in South African waters, except that they Although there is some evidence of neonates on the northeast coast of South Africa (Fennessy, 1994), the absence of repro- Potential threats for R. djiddensis within its range on the southern African coast include artisanal and industrial shark-directed fisheries in Mozambique (Pierce et al., 2008). Such fisheries are driven by the high demand for and value of shark fin (including the fins of shark-like rays), especially those of R. djiddensis, which are a primary target species for the global fin trade in many areas in the region (Moore, 2017;Jabado, 2018;. The smallscale fishing sector (artisanal and subsistence fishers) in Mozambique is also extensive along most of the coastline, and has accounted for an estimated 75% of total annual fishery catches over the past five decades, with R. djiddensis considered to contribute a significant annual catch to this sector (Doherty et al., 2015). ...
Article
• The white‐spotted wedgefish (Rhynchobatus djiddensis) is a Critically Endangered shark‐like ray in the family Rhinidae. Throughout its Western Indian Ocean distribution, it is targeted for its valuable meat and fins and is reported to have undergone major population declines. However, there remains a need for species specific time‐series data to accurately assess localized population declines. • This study used two independent long‐term (37 and 40 years) time‐series catch data from competitive shore angling and shark nets to investigate the size composition and catch per unit effort (CPUE) and conduct a risk assessment for the population on the east coast of South Africa. • From 1977 to 2017 the competitive shore fishery captured 7,703 individual R. djiddensis, whilst shark nets in the same region captured 2,856 individuals from 1981 to 2017. Individuals captured in the nets had a sex ratio of 1.8:1 females to males, and were larger than those caught by the anglers. Although the mean annual sizes of net‐caught individuals were above the size of reported sexual maturity, there was little evidence to suggest that any individuals captured were reproductively active. • Both the competitive shore fishery and shark net catches exhibited strong seasonal trends with the majority of R. djiddensis catches occurring from October to May peaking in austral summer. Standardized CPUE from the competitive shore fishery declined substantially between 1977 and 2017 and shark net catches exhibited a significant (p < 0.05) fourfold decline in annual nominal CPUE from 1981 to 2017. • Ultimately, a risk assessment showed a 65.1% decline in abundance over a period of three generation lengths, which indicates that the sampled population of R. djiddensis in South Africa should be classified as Endangered according to the IUCN Red List using criterion A2b. The conservation implications of this are discussed.
... Since 1985, the majority of shark catches in Bangladesh were thought to come from artisanal fisheries, mostly from gill net, set bag net, and hook and line fisheries (Haldar, 2010), and both directed take and high levels of bycatch may be factors in the declines in sawfish observations over recent decades (Hossain et al., 2015). Similar declines have been reported from many parts of the northern Indian Ocean, southern India (Joel & Ebenezer, 1999), Oman, and the Arabian Gulf (Jabado, 2018;Jabado et al., 2017). Sawfishes have been globally exploited, primarily for their fins but in some areas also for their skin, meat and rostra . ...
Article
1. Sawfishes are highly threatened globally, and current data on their conservation status in the Indian Ocean are limited. A baseline study conducted in 2011–2012 revealed that at least two species of sawfish were still present in Bangladeshi waters and highlighted several important steps that could be taken to prevent populations from further decline. 2. Regular visits to landing sites in the south-eastern coastal region of Bangladesh were conducted to collect data on sawfish landings. A telephone reporting system was developed amongst shark traders and fishers, to facilitate immediate reporting of sawfish landings. 3. Between 15 October 2016 and 26 December 2017, landings of 25 sawfishes were documented, of which at least 17 were largetooth sawfish Pristis pristis. No evidence of narrow sawfish Anoxypristis cuspidata was observed, which may suggest that this species has become rare. 4. These data were collected 5 years after the baseline study was conducted and after several years of broader efforts to highlight the precarious status of sawfish populations globally. The findings illustrate that largetooth sawfish continue to be landed and that none of the management or community engagement activities previously recommended, in order to reduce catch rates, have been implemented. 5. This is an example of the research–practitioner divide, where published scientific research on a group of highly endangered elasmobranchs has not led to their protection. A strategy for communicating the findings of this study and the critical need for local conservation action for sawfishes to key national and local stakeholders is presented, alongside a suite of actions that can be feasibly implemented in the next 12 months.
... These studies have highlighted that most sawfish populations have drastically declined across their regional range in addition to a documented local extinction having occurred in South Africa (Everett et al., 2015). Given the increasing awareness of these species and their distinctive appearance, occasional sightings are now reported through various media outlets as well as from fisheries-dependent data including from Bangladesh (Chowdhury, Sabbir & Haque, 2018;Haque & Das, 2019;Haque, Leeney & Biswas, 2020), the UAE (Jabado, 2018), Sudan (Elhassan, 2018), India (CMFRI, 2015;CMFRI, 2018;Purushottama et al., 2020), Qatar, Iran, and Bahrain (Fordham et al., 2018). However, to date, few sawfish reports have emerged from Sri Lanka and therefore their occurrence in these waters remains uncertain with no dedicated study undertaken to determine their status. ...
Article
• All five species of sawfishes (family Pristidae) are amongst the most threatened marine fishes in the world, with steep population declines and local extinctions documented across their ranges. • Sawfishes have featured in Sri Lankan species checklists since 1889. However, landing records are extremely rare and little information is available on their status, diversity, and recent occurrences. • Interviews were conducted with 300 fishers and 10 fish traders. Only 39% of fishers (n = 118) could identify sawfishes, 37% had seen sawfishes (although half not since 1992), and only 10.7% had ever caught one. No respondents under 30 years could identify sawfishes. Older respondents (>50 years) were more likely to have caught sawfishes and reported seeing them frequently until 30 years ago, while younger respondents had only seen them at landing sites and, at most, once or twice in their life. Only 10 respondents had seen a sawfish in the last decade, suggesting that sawfishes were relatively abundant in the past but that populations have drastically declined. • Of the 32 respondents who had caught sawfishes, 30 reported declining numbers and attributed it to fishing pressure. These steep declines coincide with the time of increased fishing effort, the development of the aquaculture industry, and resulting degradation of coastal habitats in the 1980–1990s. • Overall, sawfishes had little cultural significance although fishers had specific names for the different species occurring here and rostra were sometimes donated to Catholic churches for ‘good luck’. Landed sawfishes were primarily sold for meat and traders appeared unaware of the high value of fins. • It is likely that sawfishes are now functionally extinct as a component of coastal ecosystems in Sri Lanka. Immediate action including species-specific legislation and critical habitat protection is urgently needed to provide remaining sawfishes and other sharks and rays with a fighting chance.
... The most sought-after and most valuable species (i.e. hammerhead sharks, pigeye sharks, bull sharks, hammerhead sharks, tiger sharks, sawfishes, wedgefishes and guitarfishes) (Okes and Sent, 2019;Clarke et al., 2007;Jabado et al., 2015;Jabado, 2018;Kyne et al., 2020;Haque et al., 2020) are also the most vulnerable, globally, based on IUCN Red List criteria (IUCN, 2021). Our study showed that, based on interviews with elasmobranch traders, the majority of elasmobranch products were exported to Myanmar between 2014 and 2017 as a conduit to China and Hong Kong. ...
Article
Trade in elasmobranch products is a circum-global practice negatively impacting elasmobranch populations. Although Asia is at the centre of the shark fin trade, countries like Bangladesh, remain data-poor regarding trade dynamics. In the Bay of Bengal region, Bangladesh has a long-standing history of producing and trading products from vulnerable and protected elasmobranchs both nationally and internationally. A limited understanding of trade currently precludes Bangladesh from enforcing regulations effectively and taking timely conservation actions. To address this knowledge gap, we characterized elasmobranch trade by identifying stakeholders involved in national and international trade, routes used, trade hubs, and ports in Bangladesh. We found that most of the trade remains unreported and violates the Wildlife (Conservation and Security) Act, 2012 and CITES mandates. We identified the south-eastern region as a trade hub with a syndicate of traders annually exporting elasmobranch products predominantly to China via Myanmar. High-quality fins and dried meat drive international trade, including products from Critically Endangered sawfish (Pristidae), guitarfishes (Glaucostegidae, Rhinobatidae), wedgefishes (Rhinidae), hammerhead sharks (Sphyrnidae), and large requiem sharks (Carcharhinidae). Also prevalent is a substantial national demand for elasmobranchs for consumption and traditional medicinal uses. Apart from limited alternatives, a low efficiency of acquiring maximum profits in trading other fishery products, an inequality of profit sharing and limited awareness of laws amongst traders results in their non-compliance towards the Wildlife Act, 2012. Along with amendments to this national Act, it is essential to protect threatened species beyond just legal regimes. Enhanced monitoring and inclusive policies are essential for disincentivizing traders to trade such products.
... This species belongs to the batoid family Rhinidae (wedgefishes), which are large benthopelagic shark-like rays (Giles et al. 2016). Rhynchobatus djiddensis is exploited by fisheries that are driven by the high value of their fins in international trade, and declines have been noted throughout their range (Moore 2017;Jabado 2018). A recent trend shows that the fins of wedgefishes are becoming more common in the shark fin trade (Fields et al. 2018). ...
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In recent decades, a combination of increasing demand and economic globalisation has created a global market for elasmobranch products, especially the highly prized shark fins for Asian markets. Morphological species identification, as well as traditional cytochrome c oxidase subunit I (COI) barcoding of shark fins and other products, become challenging when in a processed state (such as dried or bleached shark fins). Here a mini-barcoding multiplex assay was applied to determine the species of origin in case studies from southern Africa involving confiscated shark fins in different states of processing. This highlights that the illegal shark fin trade in southern Africa to a large extent comprises threatened species. Matching of sequences of the confiscated fins against public databases revealed several threatened species, including the CITES-listed species Carcharodon carcharias, Carcharhinus longimanus, Isurus oxyrinchus, Rhynchobatus djiddensis and Sphyrna lewini. The findings highlight the need for improved trade monitoring, such as to eliminate illegal trade in shark fins, which can in part be achieved through more widespread genetic sampling of internationally traded products. However, a major limitation to DNA barcoding in general lies in the lack of curated voucher specimens available on public databases. To facilitate the application of molecular methods in a more comprehensive evaluation of elasmobranch trade regionally, a concerted effort to create reliable curated sequence data is recommended.
... The occurrence of large shark-like rays and stingrays and their high economic value have previously been used as justification for the continuation of the tangle net fishery (Amir, 1988). Given the current declining state of several batoid populations in South-East Asia (IUCN, 2021) and the scale of Indonesia's shark fishery (Jaiteh et al., 2016), the contemporary catch of the tangle net fishery is probably not sustainable. However, the exact impact of the present-day tangle net fishery is unknown and requires detailed investigation, especially considering the impacts of other fisheries affecting different size classes and the declines of batoid populations across South-East Asia. ...
Article
• Shark-like rays (Order Rhinopristiformes) are among the most threatened families of marine fish, yet little is known about their populations. These rays are normally taken as opportunistic catch in fisheries targeting other species and are thus poorly reported. One exception is the Indonesian tangle net fishery, which targets shark-like rays. • Market surveys of Muara Angke landing site in Jakarta, north-western Java were conducted between 2001 and 2005, and the landed catch from the tangle net fishery was recorded (the Muara Angke landing site includes landings from more than one fishery). • In total, 1,559 elasmobranchs (sharks and rays) were recorded, comprising 24 species of rays and nine species of sharks. The most abundant species landed were the pink whipray Pateobatis fai and the bottlenose wedgefish Rhynchobatus australiae, the latter being the main target species. • Catch composition varied based on differences in species catchability and may also be indicative of localized declines. The fishery was highly selective for larger sized individuals, while smaller size classes of many ray species, including the target species, were also caught in other Indonesian fisheries, resulting in fishing pressure across all age classes. • The decline of tangle net vessels in the fishery and the potential shift in catch composition in the Indonesian tangle net fishery increase concerns about the status of shark-like rays and stingrays in Indonesia.
... The geographic range of P. prahli was documented as from the Gulf of Tehuantepec in southeastern Mexico south to northern Peru, but it has recently been expanded to include the peninsula of Baja California (Rutledge 2020). Documentation of species ranges is essential for implementing effective conservation strategies, especially since guitarfishes are among the most threatened groups of sharks and rays, due to their slow growth, low fecundity, and being an important target of fisheries worldwide (Dulvy et al. 2021, Jabado 2018, Moore 2017. Additional research into the biology, ecology, and population status of species such as Z. exasperata and P. prahli is necessary to improve conservation efforts and assess changes due to changing climate and oceanographic conditions. ...
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The recent ocean-warming events along the California coast have extended the northern range of several elasmobranch species. The Banded Guitarfish, Zapteryx exasperata, is a poorly known shallow-water batoid, typically found in warm-temperate to tropical waters of southern California, USA and the Gulf of California, Mexico. During a Baited Remote Underwater Video Station (BRUVS) survey in October 2020, an unusual batoid identified as Z. exasperata was observed at a depth of 2.5 m. This individual was within the Point Lobos State Marine Reserve in Monterey County, central California, extending its range by at least 260 km northwards. A key to the California species of guitarfishes and Thornback Ray is provided.
... This selective habitat preference leaves these species susceptible to coastal development, habitat degradation and pollution and their distribution overlaps with some of the world's major fisheries (Kyne et al., 2020). This array of anthropogenic threats has led to drastic population declines being documented over a short period of time from regions of the world where data are available (Jabado, 2018;Kyne et al., 2020;Moore, 2017). Species specific landings data from Indian waters are scant, although data from the east coast indicate that landings of 'guitarfishes' (wedgefishes (family Rhinidae) and giant guitarfishes) declined by 86% between 200286% between and 200686% between (Mohanraj et al., 2009. ...
Article
For elusive, data-poor marine fauna, Local Ecological Knowledge (LEK) can be a rich and often underutilised source of biological and ecological data. We used a socio-ecological approach to assess LEK and provide key insights into the distribution, habitat use pattern, and threats facing giant guitarfishes (Glaucostegus spp.) in the Andaman Islands, India. We interviewed 175 fishers and other coastal users (SCUBA divers, coastal residents, researchers etc.), 142 of whom had seen giant guitarfishes. Due to the difficulty in distinguishing between species of this genus, this study did not attempt to collect species specific data. However, data presented here most likely refer to the Giant Guitarfish (Glaucostegus typus) as it is the only species from this family confirmed from the Andaman Islands. Our results show that LEK can be an invaluable asset in understanding the distribution of little-known species. With sightings from over 70 locations, our data indicate that giant guitarfishes occur widely and the frequent sightings of pup-sized (<45 cm) individuals in shallow coastal waters suggests they could be using these habitats as nursery grounds. The identification of several potential nursery areas highlights locations of their range that need urgent protection to aid in their conservation. The only other location where G. typus is reportedly still frequently observed is northern Australia, making the Andaman Island population globally significant. However, rapid coastal transformation and growing fisheries likely threaten the species. With more than 33% of reported observations being over a decade old, our data suggest that populations have drastically declined, highlighting the need to regulate fisheries and coastal development in the Andamans. Including giant guitarfishes under the Indian Wildlife Protection Act would also be an essential step towards managing this globally important population.
... The dramatic decline of Wedgefishes in the western Indian Ocean is due to them being targeted for their high-value, and international demand for, 'white' fins (Dent and Clarke, 2015;Moore, 2017). These two families have now been classified as the two most imperilled marine fish families globally (Jabado, 2018;Moore, 2017). These species are particularly vulnerable given that they display limited biological productivity, are present in shallow waters where coastal fishing pressures peak and are vulnerable to both specific fisheries as well as being bycatch in other fisheries (Kyne et al., 2019b). ...
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Coral reefs are global biodiversity hotspots and one of the most vulnerable ecosystems on the planet. Human disturbances, extractive overfishing and a changing climate threaten to collapse 75% of coral reefs by 2050. Marine Protected Areas (MPAs) which prohibit all forms of human activities are documented to achieve maximum conservation benefits; however, 94% of international MPAs still allow some form of fishing. This is the case in the iSimangaliso Wetland Park (IWP), which has protected South Africa’s high latitude coral reefs (HLCRs) for over 30 years. The MPA within IWP is zoned to include No-Take Sanctuary Zones (NTSZs), which prohibit all activity, and a Controlled-Pelagic Zone (CPZ), which allow SCUBA diving and pelagic fishing but restrict all other human activities. While accommodating human needs within an MPA is essential for stakeholder acceptance, little is known about the effect of anthropogenic activity within the IWP MPA. Along with anthropogenic drivers, previous studies have conveyed that latitude, depth and habitat type are some of the key drivers in shaping coral reef fish communities. Within habitat type, available habitat area and fine-scale benthic characteristics have been highlighted as key determinants of reef fish community ecology. Whether these drivers apply to high latitude coral reef (HLCR) ecosystems remains a gap in coral reef ecosystem research. Thus, this study aimed to identify important environmental variables and the effect of different management zones on reef fish populations and communities on the HLCRs within iSimangaliso Wetland Park. This study used baited remote underwater stereo-video systems (Stereo-BRUVs) to survey habitats and fish assemblage structure within different management zones (From north to south: Maputaland NTSZ, CPZ and St Lucia NTSZ) of the IWP. Variation in the taxonomic and functional entities was defined according to three metrics, abundance, size (fork length) and abundance per maturity stage (juvenile or adult). The significant environmental drivers were then identified for both taxonomic and functional trait-based reef fish assemblages. Once habitat variability was accounted for, the effect of different management zones on assemblage structure was determined. The taxonomic and functional structure of reef fish communities consistently responded to habitat variability, with functional indices and diversity increasing in habitats associated with higher relief stony coral habitats and decreasing in low relief sandy or macroalgal habitats. When looking at individual species populations, reef size played an important role in determining the average biomass of the dominant species with larger individuals typically associated with larger reef patches. A similar pattern was detected with fish abundance, but the effect was less pronounced than with the biomass data. The significant effect of habitat variation and reef size on the fish populations and assemblages stresses the importance of accounting for habitat variability in spatial comparison studies. This finding also offers important insight into the benefit of protecting different habitat types to increase the overall diversity of fishes protected. Both NTSZs supported unique predatory functional groups and species, whereas the CPZ was characterised by juvenile species and functional groups characterised by juveniles, suggesting that the CPZ may be impacted by the permitted anthropogenic activity. Alternatively, the CPZ may serve as a unique nursery ground for juveniles, but as the habitats in the CPZ were similar to those in the NTSZs, it is not clear why this might be the case. The Maputaland NTSZ appeared to support unique fish communities with greater functional richness, attributed to the additional presence of macroalgal habitats, which were absent from the other zones of the MPA. Single species analysis suggested that Lethrinus crocineus and Epinephelus tukula, which are both protected throughout the MPAs, were affected by the anthropogenic activity within the CPZ, as they were typically smaller and less abundant in the CPZ relative to the NTSZs. In agreement with my findings, previous studies in the area have identified that E. tukula is negatively influenced by high diving pressure that occurs in the CPZ. Alternatively, populations of Caranx melampygus and Aprion virescens, which are both permitted to be captured in the CPZ, appeared to benefit from the additional protection within the NTSZs and demonstrated direct impacts of past and present fishing pressure within the CPZ. The populations of A. virescens, C. melampygus, E. tukula and L. crocineus all displayed potentially greater abundance or biomass, or both, within the St Lucia NTSZ as compared to the Maputaland NTSZ. The fact that the St Lucia NTSZ is older than the Maputaland NTSZ may be the driving factor of this pattern. As for Lutjanus bohar and Variola louti, there were demonstrations of habitat preferences, however, there were no significant differences in the abundances and biomasses between different management zones when accounting for habitat variables. These results demonstrate that the NTSZs, which encompass large reef complexes and a variety of benthic habitat types, is working as a management strategy for protecting unique assemblages and larger fish on HLCRs of the IWP. Nowadays, NTSZs often exist only because human needs are accommodated in other zones of an MPA. In the IWP example, the permitted activity in the CPZ generates substantial income for the local communities and as such generates local support for the MPA. However, my findings do demonstrate that the permitted activity in the CPZ is, directly and indirectly, affecting different species of fishes, and it is recommended that controlled zones within MPAs allow for adaptive management, long term monitoring and to enhance the conservation potential of these zones.
... Landings data indicate that the most abundant taxa are the cownose rays (Rhinoptera spp.) (59.4% of ray landings), eagle rays (Aetomylaeus spp.) (20.6%), and wedgefishes, Rhynchobatus spp. (10.5%) 34 (Jabado, unpubl. data). ...
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Data on the diversity and relative abundance of elasmobranchs (sharks and rays) in the Arabian Gulf have been limited to fishery-dependent monitoring of landing sites. Understanding the diversity and abundance of sharks and rays is, however, crucial to inform policy and management plans. Baited Remote Underwater Video Surveys (BRUVS) were conducted in 2015–2016 across the United Arab Emirates Arabian Gulf waters encompassing a range of depths and habitat types. Data from 278 BRUVS (757 hours soak time) were analysed to gather information on diversity, relative abundance, species distribution, and habitat associations. Surveys recorded 213 individuals from 20 species of sharks and rays at 129 stations. The frequency of occurrence of species usually discarded by fishers such as the Arabian carpetshark (Chiloscyllium arabicum) and stingrays (Himantura spp.) was high, accounting for 60.5% of observed elasmobranchs. Despite the large survey area covered and extensive sampling effort, the relative abundance of sharks and rays was low at 0.28 elasmobranchs per hour, 0.13 sharks per hour, and 0.15 rays per hour. This CPUE was reduced to one of lowest recorded abundance on BRUVS from around the world when removing the two discarded species from the analysis (0.11 elasmobranchs per hour). These results likely reflect the intense fishing pressure and habitat loss contributing to population declines of many elasmobranchs in the Arabian Gulf. Findings provide a baseline for future work and can support the design of conservation strategies for sharks and rays in the UAE.
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The species composition of batoid fishes from coastal waters of the Socotra Archipelago is reviewed, with confirmed records of the wedgefish Rhynchobatus djiddensis (Forsskål, 1775) and four new records of sharkrays, wedgefishes, and guitarfishes based on collected specimens, including one species from Abd al-Kuri Island, Rhina ancylostoma Bloch & Schneider, 1801 (Rhinidae), and three species from the main island Socotra, Acroteriobatus salalah (Randall & Compagno, 1995) and Rhinobatos punctifer Compagno & Randall, 1987 (Rhinobatidae), and Rhynchobatus australiae Whitley, 1939 (Rhinidae). Among the new records for the Socotra Archipelago, R. australiae represents the first verified record for the Arabian region. In addition, records of four stingray species (Dasyatidae) are verified based on underwater observations accompanied with photographs. All recorded batoid fishes are commercial species caught in the local small-scale fishery. Information on the identification and distribution of each species is provided.
Article
Information on the movement ecology of endangered species is critical for the implementation of effective conservation measures. This study made use of a long-term dart tagging dataset to reveal the movement patterns and growth rates of two size classes of the Critically Endangered whitespotted wedgefish Rhynchobatus djiddensis within its southern African distribution, which can have important implications for fisheries management. A total of 4 768 individuals were tagged with 340 recaptures recorded, ranging from 1 to 2 639 days (7.2 years) at liberty. Most of the tag releases and recaptures occurred within the KwaZulu-Natal central region in South Africa, with catches increasing significantly during summer (October to March). Most recaptures (43%) were recorded within 5 km of the tagging (release) site. Tagged adults recorded significantly greater distances moved than juveniles (p < 0.002) but there was no significant difference between juveniles or adults in terms of their direction of movement (p > 0.30). A Francis growth model showed that smaller individuals had a substantially faster growth rate (198.69 [SE 21.75] mm year⁻¹) compared with larger individuals (57.41 [SE 27.83] mm year⁻¹) confirming that the species is relatively slow-growing. Ultimately, this study identified important knowledge gaps in the broadscale movement patterns of R. djiddensis and provided new information on the growth rate of this Critically Endangered species. Filling in these knowledge gaps will aid in conservation measures for two important size classes of the R. djiddensis population as the species faces increasing targeted fishing pressure.
Chapter
Rhino rays comprise 64 species of shark-like rays from five families. Over two-thirds (69%) are threatened with extinction with 41% Critically Endangered (these face an extremely high risk of extinction). All sawfishes and giant guitarfishes, 90% of wedgefishes, 59% of guitarfishes, and 38% of banjo rays are threatened. The major driver of endangerment is overexploitation either through targeted fishing or bycatch. Considering the continuing high levels of exploitation, the growing demand for their fins, and pressure on coastal habitats from human activities, the situation for these species is alarming in most areas of the world. Hotspots of threat (high levels of fishing pressure and habitat loss and degradation) include West Africa, the Northern Indian Ocean, Southeast Asia, and the Eastern Central Pacific. These areas support the majority of threatened rhino rays. Local, regional, and global efforts are required to restore and secure rhino rays. Actions need to be taken immediately and governments need to ensure that management measures are properly implemented to enable successful recovery of populations. Species protections for the most imperiled species and the effective enforcement of existing international trade regulations for sawfishes, wedgefishes, and giant guitarfishes are critical.
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Background Expanding fisheries in developing nations like Sri Lanka have a significant impact on threatened marine species such as elasmobranchs. Manta and devil (mobulid) rays have some of the most conservative life history strategies of any elasmobranch, and even low to moderate levels of bycatch from gillnet fisheries may lead to significant population declines. A lack of information on life history, demographics, population trends, and fisheries impacts hinders effective management measures for these species. Method We report on mobulid fishery landings over nine years between 2011 and 2020 across 38 landing sites in Sri Lanka. We collected data on catch numbers, body sizes, sex, and maturity status for five mobulid species. We used a Bayesian state-space model to estimate monthly country-wide catch rates and total annual landings of mobulid rays. We used catch curve analyses to estimate total mortality for Mobula mobular , and evaluated trends in recorded body sizes across the study period for M. mobular, M. birostris, M. tarapacana and M. thurstoni . Results We find that catch rates have declined an order of magnitude for all species across the study period, and that total annual captures of mobulid rays by the Sri Lankan artisanal fishing fleet exceed the estimated annual captures of mobulids in all global, industrial purse seine fisheries combined. Catch curve analyses suggest that M. mobular is being fished at rates far above the species’ intrinsic population growth rate, and the average sizes of all mobulids in the fishery except for M. birostris are declining. Collectively, these findings suggest overfishing of mobulid ray populations in the northern Indian Ocean by Sri Lankan artisanal fisheries. We recommend strengthening the management of these species through improved implementation of CITES, CMS, and regional fisheries management actions. In addition, we report on the demographic characteristics of mobulids landed in Sri Lanka and provide the first record of M. eregoodoo in the country.
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Sharks and rays are at risk of extinction globally. This reflects low resilience to increasing fishing pressure, exacerbated by habitat loss, climate change, increasing value in a trade and inadequate information leading to limited conservation actions. Artisanal fisheries in the Bay of Bengal of Bangladesh contribute to the high levels of global fishing pressure on elasmobranchs. However, it is one of the most data-poor regions of the world, and the diversity, occurrence and conservation needs of elasmobranchs in this region have not been adequately assessed. This study evaluated elasmobranch diversity, species composition, catch and trade within the artisanal fisheries to address this critical knowledge gap. Findings show that elasmobranch diversity in Bangladesh has previously been underestimated. In this study, over 160000 individual elasmobranchs were recorded through landing site monitoring, comprising 88 species (30 sharks and 58 rays) within 20 families and 35 genera. Of these, 54 are globally threatened according to the IUCN Red List of Threatened Species, with ten species listed as Critically Endangered and 22 species listed as Endangered. Almost 98% juvenile catch (69–99% for different species) for large species sand a decline in numbers of large individuals were documented, indicating unsustainable fisheries. Several previously common species were rarely landed, indicating potential population declines. The catch pattern showed seasonality and, in some cases, gear specificity. Overall, Bangladesh was found to be a significant contributor to shark and ray catches and trade in the Bay of Bengal region. Effective monitoring was not observed at the landing sites or processing centres, despite 29 species of elasmobranchs being protected by law, many of which were frequently landed. On this basis, a series of recommendations were provided for improving the conservation status of the elasmobranchs in this region. These include the need for improved taxonomic research, enhanced monitoring of elasmobranch stocks, and the highest protection level for threatened taxa. Alongside political will, enhancing national capacity to manage and rebuild elasmobranch stocks, coordinated regional management measures are essential.
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There is recent evidence of widespread declines of shovelnose ray populations (Order Rhinopristiformes) in heavily fished regions. These declines, which are likely driven by high demand for their fins in Asian markets, raises concern about their risk of over-exploitation and extinction. Using life-history theory and incorporating uncertainty into a modified Euler-Lotka model, the maximum intrinsic rates of population increase (rmax) were estimated for nine species from four families of Rhinopristiformes, using four different natural mortality estimators. Estimates of mean rmax, across the different natural mortality methods, varied from 0.03 to 0.59 year⁻¹ among the nine species, but generally increased with increasing maximum size. Comparing these estimates to rmax values for other species of chondrichthyans, the species Rhynchobatus australiae, Glaucostegus typus, and Glaucostegus cemiculus were relatively productive, while most species from Rhinobatidae and Trygonorrhinidae had relatively low rmax values. If the demand for their high-value products can be addressed then population recovery for some species is likely possible, but will vary depending on the species.
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Nearshore, shallow water habitats are believed to be highly important for various species of threatened sharks and rays (batoids) around the world. Yet, there is limited information on which batoid species use them. During eldwork on Siniya Island in the Emirate of Umm al-Qaiwain, United Arab Emirates (UAE), rays and guitar sh were observed on twelve occasions in shallow waters or found stranded along the shoreline. At least three species were identi ed from at least 20 individuals (adults and juveniles) consisting of the Arabian banded whipray, Maculabatis randalli, the Halavi guitar sh, Glaucostegus halavi, and cowtail rays, Pastinachus sp. Our observations highlight the importance of shallow water habitats for at least these batoids. Many coastal habitats in the UAE and broader region are currently threatened by development projects and other anthropogenic activities, highlighting the urgent need to better understand their role in maintaining shallow subtidal biodiversity.
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Rhinobatos austini sp. n. is described from the southwestern Indian Ocean based on four specimens collected from the KwaZulu-Natal Province, South Africa and from Mozambique. The new species, with one exception, can be distinguished from all other members of this genus by a prominent teardrop-shaped dark blotch on the ventral surface of its snout. Its closest congener, R. holcorhynchus, also has a prominent teardrop-shaped blotch on its snout, but the new species differs from it by a lack of prominent thorns and tubercles on it dorsal disc surface and a very striking dorsal surface colour pattern of paired spots, some forming darker transverse bands across its back. Geographically, these two species broadly overlap, but R. austini appears to be a shallow, more coastal species (<1–107 m) compared to R. holcorhynchus that has a mostly offshore (75–254 m) depth distribution.
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The sawfishes (Pristidae) represent one of the most threatened groups of marine fish around the world. Between October 2015 and June 2016, interviews (n = 82) were conducted to assess the occurrence of sawfish in United Arab Emirates waters and gain insight from fishers’ traditional ecological knowledge regarding the status, uses, and cultural significance of sawfish. Almost all respondents (95.1%) had previously seen a sawfish, and 92.6% confirmed that their numbers had declined in the last 20 yr. Most respondents reported encounters in the last 5 to 10 yr, with 18.3% (n = 15) having seen a sawfish in the last 2 yr. Sawfish were not perceived as a culturally significant resource (76.8%) and when caught were primarily used as food, their high-value fins sold to traders, and rostra retained as decorations. The consensus was that while sawfish were previously targeted, they are now caught primarily as bycatch in gill nets. Based on pictures and rostra encountered (n = 19), it appears that the green sawfish Pristis zijsron is more common in United Arab Emirates waters than the narrow sawfish Anoxypristis cuspidata, which is likely to be present off the Ras Al Khaimah coast. While the results of this study provide evidence of a large decline in sawfish, they hint at the possible importance of Abu Dhabi waters as a region where sawfish are still encountered and where research and monitoring, as well as conservation and recovery efforts, should be focused to avoid local extinction and recover their populations.
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The recently resurrected genus Acroteriobatus is represented in the western Indian Ocean by eight species, including a new guitarfish Acroteriobatus omanensis sp. nov. This small species (reaching ~60 cm TL) was discovered off Oman in an investigation of the chondrichthyan fauna of the Arabian in 2002 and 2003. Its distinctiveness from other members of the genus Acroteriobatus is strongly supported by molecular data. Acroteriobatus omanensis sp. nov. differs from all other members of the genus by its very narrowly pointed snout and having a dense pattern of small, symmetrically arranged ocelli each consisting of a white spot surrounded by a darker rim. Acroteriobatus annulatus and A. ocellatus have a more-or-less ocellated dorsal colour pattern but the markings are larger and differ in form (ocelli consisting of a small dark central spot surrounded by a dark-edged pale ring in A. annulatus; larger, irregularly shaped ocelli with pale centres surrounded by a dark brown rim in A. ocellatus).
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Extensive surveys of various fish landing sites in eastern Indonesia, conducted between April 2001 and March 2006, recorded a total of 54 species of batoid rays belonging to 12 families. The Dasyatidae was by far the most speciose family, comprising half of the recorded species, and was also the most abundant, contributing 89 and 44% to the total numbers and total estimated biomass of batoids, respectively. The size and sex compositions of 23 species of rays are described and an accurate size at maturity of males, i.e. with 95% CI, was determined for 13 of these species. The sex ratios were found to be close to parity in the majority of species, however, the landings of the whitespotted guitarfish Rhynchobatus australiae consisted of significantly more females than males, a situation also recorded for this species in the by-catch of the northern Australian prawn fishery. Data on aspects of the reproductive biology of three dasyatid species (Dasyatis cf. kuhlii, Dasyatis zugei and Himantura walga), which form a substantial component of the by-catch of the bottom trawl fisheries in the region, were collected on most sampling occasions. These small rays, i.e. maximum sizes 243–379 mm disc width, were found to have no distinct seasonal reproductive cycle and small litter sizes, i.e. less than four embryos. Opportunistic reproductive data, e.g. litter size and embryo sizes, were also collected from various other species. The litter sizes of the rhynchobatid and rhinobatid species examined were found to be larger than those of the gymnurid and dasyatid species examined, i.e. seven to 19 and two to 13 v. one to four, respectively. The data presented in this paper for the numerous species of rays which are landed by target and non-target fisheries in Indonesia represent the first such data for the vast majority of these species.
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Records of 11 elasmobranch species previously unreported from, or uncommon in, Omani waters are presented. Records new to Oman include Carcharhinus altimus, C. leiodon, Centrophorus isodon, Ctenacis fehlmanni, Himantura fai, Mobula eregoodootenke and Sphyrna zygaena, whereas noteworthy records of uncommon species include Himantura imbricata, Paragaleus randalii, Rhinobatos salalah and Taeniura meyeni – some of which are confirmed from the Gulf of Oman for the first time. These records bring to 57, the number of elasmobranch species confirmed in Omani waters.
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Growing concern for the world’s shark and ray populations is driving the need for greater research to inform conservation management. A change in public perception, from one that we need to protect humans from sharks to one where we must protect sharks from humans, has added to calls for better management. The present paper examines the growing need for research for conservation management of sharks and rays by synthesising information presented in this Special Issue from the 2010 Sharks International Conference and by identifying future research needs, including topics such as taxonomy, life history, population status, spatial ecology, environmental effects, ecosystem role and human impacts. However, this biological and ecological research agenda will not be sufficient to fully secure conservation management. There is also a need for research to inform social and economic sustainability. Effective conservation management will be achieved by setting clear priorities for research with the aid of stakeholders, implementing well designed research projects, building the capacity for research, and clearly communicating the results to stakeholders. If this can be achieved, it will assure a future for this iconic group, the ecosystems in which they occur and the human communities that rely on them.
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Theoretical models of coastal shark populations have remained largely unchanged since the 1960s despite limitations in applicability to many species. Smaller bodied coastal species are poorly represented by the current models. A new theoretical model is proposed to represent those species that spend most or all of their life within nearshore waters but do not show use of discrete nursery areas. Description of this new model outlines the importance of nearshore areas to these smaller species. While all coastal shark populations are susceptible to environmental and anthropogenic impacts, species that fit the new model are more vulnerable to varying coastal processes, habitat degradation, and fishing pressure than are species that use nearshore areas for only part of their life-span. The dynamic nature of nearshore areas and their proximity to human populations present all sharks that occur in them with a range of advantages and disadvantages. This paper reviews how different species utilise nearshore areas and how they overcome the challenges they face in inhabiting these areas. Improving and expanding theoretical models of coastal shark populations will provide a better understanding of how sharks use nearshore environments and assist in making conservation and management decisions for these regions.
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The young (neonates, young-of-the-year and juveniles) of many shark species occupy a diverse range of habitats and areas. However, the contribution of individual nurseries or habitats to an adult population is difficult to quantify. In addition, little attention has been paid to the potential importance of ‘non-nursery’ young shark habitats to the long-term sustainability of shark populations. Portfolio theory predicts that contributions from a diverse range of young shark habitats may reduce variability in the overall production of adults, and maintain population resilience. This review examines case studies of portfolio effects in teleost fish and evaluates the relevance and potential implications of these processes for shark populations. Environmental heterogeneity in young shark habitats can result in locally adapted habitat-use patterns and life history traits. Therefore, young shark habitats may be differentially impacted by anthropogenic disturbance or environmental change, with different habitats performing well at different times. In addition, increased stability in production may be achieved when the effects of localised disturbance in one area are buffered by production in others. However, the behavioural and life history characteristics of some shark species may limit portfolio effects. These include the repeated use of a narrow range of habitats or areas for reproduction, and the production of relatively stable numbers of offspring. This description of the relevance of portfolio theory to shark populations highlights the importance of maintaining habitat diversity.
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a b s t r a c t Baseline, species-specific information is largely unavailable for artisanal elasmobranch fisheries, but is essential for the monitoring of exploited populations and the development of effective management plans. Seasonal surveys were conducted during 1998–1999 in Sonora, Mexico to determine the extent and activities of artisanal elasmobranch fisheries operating in the eastern Gulf of California. Nineteen fishing sites were documented, the majority of which (84.2%) targeted elasmobranchs during some part of the year. Most small demersal sharks and rays were landed in bottom set gillnet fisheries that also targeted demersal teleosts, whereas large sharks were usually taken in directed surface longline or, to a lesser extent, drift gillnet fisheries. Rays numerically dominated sampled landings in Sonora (63.4%, n = 100,136), and catch rates exceeded those of sharks during spring and summer months. The shovelnose guitarfish, Rhinobatos productus, was the primary fishery target during these seasons. During autumn, small sharks, especially mustelids (Mustelus spp.) were numerically dominant, but rays (e.g., Dasyatis dipterura) were also caught in large numbers. Winter landings in Sonora were principally composed of mustelid sharks, which represented the greatest seasonal catch rates of all elasmobranch taxa during this study. Large sharks were of comparably minor importance, with a limited summer fishery operating in the southern part of the state. Variation in catch composition was evident in association with differential interannual environmental conditions (El N no and La N na) and seasonal temperature fluctuations. Size composition of landings varied greatly by species, but relatively small size classes of sharks and rays were abundant and large, often gravid females of several ray species (e.g., R. productus and Narcine entemedor) supported spring and summer fisheries in nearshore waters. Populations of many large shark species (e.g., Carcharhinus leucas, Carcharhinus limbatus, Carcharhinus obscurus and Galeocerdo cuvier) have likely been overfished, prompting a shift in effort towards coastal populations of smaller elasmobranchs.
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Guitarfishes are a primary component of artisanal elasmobranch fisheries and are commonly taken as trawl fishery bycatch throughout the Gulf of California. However, little is known of the life history of this species. To address this lack of critical biological information, the reproductive biology of Rhinobatos productus was investigated in the eastern Gulf of California. Development of claspers and testes indicated that males reach maturity at 53cm total length (TL). Measurements of oviducal gland, largest ovum diameter, and uterus width indicated that females >57cm TL are mature. This species possesses two functional ovaries: the ovarian cycle and gestation run concurrently. Histological analysis of oviducal glands did not provide evidence of sperm storage, but females carrying uterine capsules were observed over an extended period, suggesting the possibility of diapause in the early embryonic development. Following 4–5months of embryonic growth, pups were typically born from late June to October after a gestation period of approximately 11–12months. Width of yolk sac was inversely related to embryo length. The rate of reduction of yolk sac width suggests that embryos depend on the sac until birth. Mean fecundity was estimated to be 5 (range 1–10, s.d.=2.24) with a 1:1 sex ratio. Average size at birth was 175mm TL. Seasonally, gravid females enter shallow waters for parturition, becoming extremely vulnerable to gill nets used in the artisanal ray fishery.
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Understanding the socio-economic drivers underpinning fishers' decisions to target elasmobranchs is considered vital in determining sustainable management objectives for these species, yet limited empirical data is collected. This study presents an overview of elasmobranch catch, trade and socio-economic characteristics of Zanzibar's small-scale, artisanal fishery. The value of applying this information to future elasmobranch fisheries policy is demonstrated. In August 2015, interviews were conducted with fishers (n = 39) and merchants (n = 16) at two landing sites, Kizimkazi-Dimbani and Mkokotoni, along with the main market site in Stone Town. Additionally, elasmobranch catches were recorded across the same locations between June and August 2015. Elasmobranchs were listed as target species by 49% of fishers interviewed. Whilst most fishers (n = 30) stated that 76–100% of their household income came from fishing, there was variation in how elasmobranch catch and trade contributed. One-third of fishers (n = 36) that caught and sold elasmobranchs reported that 41–60% of their income came from elasmobranch catch. However, for some fishers (n = 8) elasmobranch catch represented 0–20% of their income, whilst for others (n = 4) it represented 81–100%. Differences in fisheries income and elasmobranch price could be attributed to several interacting factors including season, weather, fishing effort, fishing gear, target catch and consumer demand. Further, elasmobranch price was influenced by size and species. The study revealed information on catch, trade, markets and socio-economy that is important for future research, conservation and management of elasmobranchs and fisheries in Zanzibar. The methods utilised have potential for broader application to understudied, artisanal elasmobranch fisheries in the western Indian Ocean.
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The Arabian Seas Region plays an important role in the global landings and trade of sharks and rays. The United Arab Emirates (UAE) and Yemen, two countries with stark socioeconomic differences, serve as major regional trade hubs for shark and ray products and four countries (Oman, Pakistan, UAE and Yemen) supply nearly 11% of dried fin exports to Hong Kong. Yet, little information is available on the characteristics of this trade and the fisheries contributing to it. Here, we review the fisheries characteristics , trade, utilization and distribution chain of sharks and rays in 15 countries of the Arabian Seas Region based on published and grey literature, landing surveys, field observations and interviews with fishermen and traders. Although regional shark fisheries remain mostly artisanal, reported shark and ray landings represent 28% of the regional total fish production, reaching 56,074 mt in 2012 (7.3% of total world catches), with Iran, Oman, Pakistan and Yemen ranking as the primary catchers. Utilization and distribution patterns are complex, vary between landing sites and countries, and remain unmonitored. Based on widespread over-exploitation of most teleost fisheries, current exploitation levels for most sharks and rays are potentially unsustainable. The situation is exacerbated by limited research and political will to support policy development, the incomplete nature of fisheries data, as well as insufficient regulations and enforcement. A better understanding of shark and ray fisheries will be key for regulating trade, promoting conservation and developing management initiatives to secure food security, livelihoods and biodiversity conservation in the region. K E Y W O R D S chondrichthyans, conservation, extinction risk, fin trade, fisheries management, sustainability
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This study focuses on the population biology of the common guitarfish Rhinobatos rhinobatos, a cartilaginous fish listed as Endangered in the International Union for the Conservation of Nature (IUCN) Red List. Between December 2012 and January 2014, 67 individuals were collected by bottom longlining in coastal Lebanese marine waters at different ports at depths ranging from 10 to 110 m. The total length (LT ) of the specimens ranged from 50 to 143 cm, and the mean ± s.d. was 76·2 ± 19·7 cm. The most common LT classes were between 60 and 70 cm. The total mass of the specimens ranged from 410 to 10 000 g, and the mean ± s.d. was 1841 ± 1987 g. A total of 34 males and 33 females were collected, and the sex ratio was not significantly different from 1:1. The mass and LT relationship showed positive allometric growth (b = 3·096 and r(2) = 0·99), and the mean ± s.d. LT at which 50% of the individuals were sexually mature was 84·73 ± 5·81 cm for females and 78·57 ± 4·88 cm for males. The gonado-somatic and hepato-somatic indices were determined along with a condition factor, and parturition appeared to occur in winter. The primary prey items found in the fish stomachs during the autumn and winter seasons were Penaeidae. The results of this study will help to parameterize models of the population dynamics for this exploited fish stock to ensure the long-term sustainability of its fishery.
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OVERVIEW Segregation of the sexes within a species is a widespread behavioural phenomenon in both terrestrial and aquatic animals. In the marine realm, sexual segregation is exhibited by many taxa including whales, seals, seabirds and fish. Of the latter group, sharks may be particularly appropriate model animals to test theories on the mechanisms underlying sexual segregation, because sexual segregation is a general characteristic of shark populations, with both sexually dimorphic and monomorphic species being well represented among the approximately 400 extant species (Springer, 1967; Compagno, 1999). The reproductive modes of sharks are diverse ranging from egg-laying (oviparity) to placental live-bearing (viviparity) (Wourms & Demski, 1993). Among sexually dimorphic, viviparous shark species it is generally the female that is larger than the male, whilst in some oviparous species males are larger than females. Sexually monomorphic species also occur. Therefore, sharks possess a number of characteristics that make them an interesting alternative to terrestrial animal models for investigating the causes of sexual segregation. In this chapter the prevalence and nature of sexual segregation in sharks is described and the relationship with reproductive modes is explored. Hypotheses suggested to account for sexual segregation in sharks are examined with respect to new field and laboratory behaviour studies of males and females of a monomorphic species, the lesser spotted dogfish ( Scyliorhinus canicula ). The chapter concludes by drawing together the main points from all shark studies to date, and suggests future directions for research in this area. © Cambridge University Press 2005 and Cambridge University Press, 2009.
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Knowledge of movements and habitat use is necessary to assess a species' ecological role and is especially important for mesopredators because they provide the link between upper and lower trophic levels. Using acoustic telemetry, we examined coarse-scale diel and seasonal movements of elasmobranch mesopredators on a shallow sandflat in Shark Bay, Western Australia. Giant shovelnose rays (Glaucostegus typus) and reticulate whiprays (Himantura uarnak) were most often detected in nearshore microhabitats and were regularly detected throughout the day and year, although reticulate whiprays tended to frequent the monitored array over longer periods. Pink whiprays (H. fai) and cowtail stingrays (Pastinachus atrus) were also detected throughout the day, but were far less frequently detected. Overall, there was no apparent spatial or temporal partitioning of the sandflats, but residency to the area varied between species. In addition, ray presence throughout the year suggests that previously observed differences in seasonal abundance are likely because of seasonal changes in habitat use rather than large-scale migrations. Continuous use of the sandflats and limited movements within this ray community suggests that rays have the potential to be a structuring force on this system and that focusing on nearshore habitats is important for managing subtropical ray populations.
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Catches of elasmobranchs in India showed an increasing trend from 27.4 thousand t in 1961 to 49 thousand t in 2006. During 2006, among the total elasmobranch catches throughout India, Tamil Nadu contributed substantially with 10.8 thousand tonnes. Observations on elasmobranchs fishery in Chennai for a period of 5 years from 2002–2006 was carried out. In Chennai fisheries harbor, annual elasmobranch catches varied from 489 t to 1735 t for the trawlnets and 194 t to 519 t for mechanized gillnets. In the same harbor, maximum catch of 2074 t of elasmobranchs was recorded in 2002. The contribution of elasmobranch i.e. 4.0 %, 16.0 % & 2.0 % to the trawl, gillnet, and hooks and line (H&L), respectively, with the CPUE of 24.4, 136.7, and 1.3 kg in the respective gears were observed. Trawlers landed heavy catch of more than 100 t of elasmobranchs during June and July with the catch per hour (cph) of 1.4–1.6 kg. Gillnet catches were better during June-September, where monthly catch was above 35 t with CPUE of 203-287 kg. H&L landed good catch during February and March, where the catch was above 1 t with the CPUE of 3.3-4.0 kg. Catch using trawlnets was dominated by sting rays (74.1%), whereas Carcharhinid sharks (51.1%) were dominant in the catch by mechanized gillnet. The elasmobranchs fishery in Chennai constituted 13 species of sharks, 13 species of rays, and 4 species of guitar fishes. Hammer head shark, Sphyrna lewini (S. lewini), was dominant among the sharks, with 33.8%, 35.0%, and 37.5% contribution in the trawlnet, mechanized gillnets, and H&L catches respectively, followed by C.sorrah and the bull shark Carcharhinus leucas (C.leucas). Among the rays, the contribution of stingray D. jenkinsii to the catch was 38.7% using the trawlnets, 31.5% using the gillnet, and 57.8% using the H&L, followed by the lesser devil ray Mobula diabolus (M. diabolus). Of the four species of guitarfishes, Rhynchobatus djeddensis was dominant. The range of size recorded for D. jenkinsii in the trawl catch was 150-1199 mm, whereas the range was from 950 to 2599 mm for S. lewini in the gillnet catch. A change in the pattern of fishery was observed during the study period. From 2003 onwards, decrease in the catch of devil ray M. diabolus (27.1-148.0 t) was observed. Increase in the catch of bull shark C. leucas (5.1–105.4 t) and thresher shark Alopias vulpinus (0.9-28.9 t) and decrease in the catch of milkshark Rhizoprionodon acutus and spadenose shark Scoliodon laticatus were also recorded. The price structure and export markets of various by-products are given.