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1.
  1. Devil rays of the genus Mobula are subject to fishing exploitation worldwide and are considered vulnerable to overexploitation due to population reduction, which is evidenced by a decline in the number of catches of these animals.
  2. Limited biological knowledge on these species has forced the use of precautionary conservation measures in countries where intensive fishing occurs.
  3. This study aimed to describe biological data of interest for estimating the feasibility of the recovery of Mobula populations, emphasizing the reproductive activity of three endangered species of the genus Mobula (Mobula munkiana, Mobula thurstoni, and Mobula mobular) in the Gulf of California.
  4. Reproductive organs were collected during 7 years of commercial fishing (2001–2007), and data on population structure, sex ratio, gamete production, and the number of offspring per breeding period were obtained.
  5. Maturity stages were determined through histological analysis of the gonads for both sexes, and the size at maturity was estimated based on anatomical and histological characteristics of the specimens caught.
  6. Considering the wide global distribution of Mobula species, there is an urgent need to apply strict conservation measures, such as established fishery closures during the breeding season or the establishment of catch periods after specimens have reached sexual maturity, especially in the countries where these animals are caught.
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2.
  1. Devil rays (Mobula spp.) are globally threatened cartilaginous fishes that have attracted global conservation concern owing to their high extinction risk and lack of protection in many countries. Limited resources and data on threatened marine species, including devil rays, impede conservation actions, particularly in developing countries, many of which have high biodiversity.
  2. Devil ray catch is a component of artisanal fisheries in Bangladesh, but data on their fisheries and trade are limited. To characterize devil ray fishing practices, fishers’ perception and trade, 230 fishers and traders were interviewed between 4 June 2018 and 22 June 2019, in four areas of south-east Bangladesh. Catch data were also opportunistically collected at landing sites.
  3. Six devil ray species were documented, caught in an array of gill nets, set-bag nets and longlines. All interviewed fishers reported life-long devil ray bycatch in some numbers, and also noted a decline in catch over the last decade. Bottom trawling, increased bycatch levels, increased demand for devil ray products and, in some cases, ecosystem changes were identified by fishers as threats to devil ray populations.
  4. Unregulated and undocumented trade and retained bycatch, especially by gill nets and set-bag nets, are fuelled by local consumption of devil ray meat and international trade in meat and gill rakers. Compliance with international trade control treaties for all Mobula spp. or the Bangladeshi law protecting Mobula mobular was low, with the majority of fishers (87%, n = 174) unaware of their existence.
  5. To manage devil ray fisheries, and prevent possible population declines, we propose a combination of legally enforced gear modifications, and catch and trade control through community-owned implementation strategies. Additionally, we propose the simultaneous implementation of inclusive, community-based awareness and stewardship projects in conjunction with a coast-wide ray monitoring programme. Finally, we emphasize that more research and action rooted in a sustainable fishery model is urgently needed to protect Bangladeshi devil ray populations.
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3.
  1. Understanding the factors driving population structure in marine mammals is needed to evaluate the impacts of previous exploitation, current anthropogenic threats, conservation status, and success of population recovery efforts.
  2. Sperm whales are characterized by a worldwide distribution, low genetic diversity, complex patterns of social and genetic structure that differ significantly within and between ocean basins, and a long history of being commercially whaled. In Australia, sperm whales from the (International Whaling Commission assigned) southern hemisphere ‘Division 5’ stock were very heavily exploited by whaling.
  3. The present study assessed the potential effects of whaling on the genetic diversity of sperm whales in Australia and the population genetic structure of these whales within a global context. A combination of historical and contemporary sperm whale samples (n = 157) were analysed across six regions, from south-eastern Australia (‘Division 6’ stock in the Pacific Ocean) to south-western Australia (‘Division 5’ stock in the Indian Ocean).
  4. Sperm whales sampled from the ‘Division 5’ and ‘Division 6’ stocks belong to the same population based on nuclear and mitochondrial DNA (mtDNA) analyses. Four novel sperm whale mtDNA haplotypes were identified in animals from Australian waters. Levels of genetic diversity were low in Australian sperm whales but were similar to those previously reported for populations in the Indian and Pacific Oceans.
  5. Given the genetic distinctiveness of sperm whales in Australian waters from other regions in the Pacific and Indian Oceans, and the lack of recovery in population numbers, further scientific studies are needed to increase our understanding of population dynamics and the effectiveness of threat management strategies in this species.
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4.
  1. Scutellastra mexicana is the largest known patellid limpet species and probably is one of the most endangered marine invertebrates.
  2. The species was once distributed along the American Pacific coast from Mexico to Peru, but their large size (up to 35 cm long) and easy accessibility (shallow sublittoral), made it very vulnerable to human collection and now is extinct on most of the mainland Mexican coast.
  3. In August 2017, a large population of this species was found on María Cleofas island, off the coast of west‐central Mexico (Marías Archipelago, Pacific Ocean). This constitutes the only report of a population of this species since 1988.
  4. A total of 808 adult individuals of up to 26 cm in length and 20 cm in width were estimated, together with the presence of juveniles, suggesting that it is a self‐sustaining population. The population was monitored in August 2017 and August 2018.
  5. Although the species is under the category ‘Special Protection’ in the General Mexican Wild Law, and that María Cleofas island is a Biosphere Reserve, fishermen that operate with impunity in the area decimated the limpet population within a year of its discovery. Abundance in the shallowest area decreased significantly from 120 individuals per transect (65 m long and 2.75 m wide) in August 2017 to 48 individuals in August 2018, and the estimated adult population decreased from 808 to 304 limpets.
  6. Neither passive national conservation policies nor local practices have reduced current threats to biodiversity and resource depletion in Marías Archipelago. Protected areas like this are ‘paper parks’—parks in name only—because there is no active conservation strategy or protection of marine species.
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5.
  1. The freshwater mussel (Unionida) fauna of the Yangtze River is among the most diverse on Earth. In recent decades, human activities have caused habitat degradation in the river, and previous studies estimated that up to 80% of the mussel species in the Yangtze River are Threatened or Near Threatened with extinction. However, a comprehensive and systematic evaluation of the conservation status of this fauna has yet to be completed.
  2. This study evaluated the conservation status of the 69 recognized freshwater mussel species in the middle and lower reaches of the Yangtze River, using the criteria published by the International Union for Conservation of Nature (IUCN). A new method for prioritizing species for conservation was then developed and applied termed Quantitative Assessment of Species for Conservation Prioritization (QASCP), which prioritizes species according to quantifiable data on their distribution and population status, life history, and recovery importance and potential.
  3. IUCN assessments showed that 35 (51%) species in the study region are Threatened or Near Threatened (11 Endangered, 20 Vulnerable, 4 Near Threatened). In addition, 16 species (23%) could not be assessed owing to data deficiency. Key threats to the freshwater mussel biodiversity of the Yangtze River include pollution, habitat loss and fragmentation, loss of access to host fish, and overharvesting of mussels and their host fish. The genera Aculamprotula, Gibbosula, Lamprotula, Pseudodon, Ptychorhynchus, and Solenaia were identified as particularly threatened.
  4. Data availability allowed QASCP assessment of 44 species. Only Solenaia carinata, regionally Endangered under IUCN criteria, achieved the highest QASCP rank, i.e. First Priority. The five species assessed as Second Priority were considered either regionally Endangered (one), Vulnerable (three), or Data Deficient (one) under IUCN criteria. The 23 Third Priority species were assessed as regionally Endangered (two), Vulnerable (15), Near Threatened (two), or Least Concern (four).
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6.
  1. The sand tiger shark (Carcharias taurus) is a coastal species distributed in temperate and sub‐tropical waters, classified as ‘Vulnerable’ at global level and ‘Critically endangered’ in eastern Australia, south‐western Atlantic Ocean, and Mediterranean Sea. Six populations (north‐western Atlantic, Brazil, South Africa, Japan, eastern Australia, and western Australia) with low genetic diversity and limited gene flow were identified worldwide, but genetic information for many other geographic areas are still missing. Specifically, this species is listed in several reports as part of the Mediterranean fauna, even if there has been a lack of catches and sightings in recent years in this basin. To clarify the origin of C. taurus individuals caught in the past in the Mediterranean Sea, historical samples were genetically analysed.
  2. Nine samples with certain Mediterranean origin were collected from different European museums. DNA was extracted and ~600 bp of the mitochondrial DNA control region were amplified using eight overlapping species‐specific primer pairs. Sequences obtained were aligned with all the haplotypes globally known so far.
  3. Genetic analysis revealed the misidentification of one museum specimen. Among the remaining Mediterranean historical samples, three different haplotypes were recovered. Two of them previously observed only in South Africa and one described in both South African and Brazilian populations.
  4. Results suggest a genetic relationship between Mediterranean sand tiger sharks and those from the western Indian Ocean. According to previous studies, we hypothesized that, during the Pleistocene, the cold Benguela upwelling barrier was temporarily reduced allowing the passage of C. taurus individuals from the Indian to Atlantic Ocean. After the restoration of this phylogeographic barrier some individuals were trapped in the Atlantic Ocean and probably migrated northward colonizing the western African coasts and the Mediterranean Sea.
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7.
  1. In Panama, shark fisheries were initially developed in the 1980s and progressively increased in production in the 1990s mainly due to the high demand for shark fins and meat from the international Asian market. Since then, and despite the exploitation rate (average 3,514 t year–1) and endangered status of some species, shark fisheries have seldom been studied, and official statistics are general or incomplete and not suitable for the development of appropriate conservation and management strategies.
  2. To understand the dynamics of shark fisheries in Panama, field surveys were conducted between 2007 and 2009 at several landing ports of small‐scale and industrial fisheries, at fish processing plants and on‐board fishing vessels in Pacific Panama, where most of the fishing vessels of the country operate.
  3. In general, it was found that the artisanal and industrial fisheries of the Pacific coast of Panama regularly exploit at least 18 species of sharks, which are also being exploited by neighbouring countries in the eastern Pacific, suggesting the importance of coordinated conservation initiatives across the multiple jurisdictions. A large number of the individuals caught were immature, implying a certain level of impact on recruitment rates. This pattern was particularly evident in species such as Sphyrna lewini, for which immature individuals represented at least 99% and 63% of the total catch by small‐scale and industrial fisheries, respectively. Catch per unit of effort analyses showed that Carcharhinus and Sphyrna species were the most exploited (representing ~80% of the catches) by industrial fisheries in Panama between 2006 and 2009, suggesting that fishery management should provide special attention to these groups.
  4. It is expected that the information presented here provides a baseline to develop new regulations, including the implementation of annual quotas and fishing seasons and the protection of nursery areas, for the long‐term sustainability and conservation of sharks in Panama.
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8.

9.
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10.
  1. The illegal sale of endangered elasmobranchs has been recorded in a number of different Brazilian states, where sharks and rays are being marketed primarily as ‘cação’ or ‘viola’. Brazil is ranked among the top 10 nations worldwide that harvest most sharks, causing an immeasurable impact on the local elasmobranch populations.
  2. The present study applied the DNA barcoding technique, based on the cytochrome C oxidase subunit I gene, for the molecular identification of the elasmobranch species sold as processed products under the generic names of ‘cação’, ‘mangona’, ‘azul’, ‘cambeva’, ‘fiuso’ and ‘lombo preto’, in the fish market of the city of Florianópolis, capital of the state of Santa Catarina, Brazil.
  3. Nine elasmobranch species were identified in the 56 samples analysed, including six sharks and three rays, representing six families, the Carcharhinidae, Sphyrnidae, Squatinidae, Arhynchobatidae, Myliobatidae and Gymnuridae. Prionace glauca, identified in more than half (56%) of the samples analysed, is listed as Near Threatened by the International Union for the Conservation of Nature.
  4. Six species identified in the present study, Sphyrna zygaena, Sphyrna lewini, Squatina guggenheim, Carcharhinus signatus, Gymnura altavela and Rioraja agassizii, are under some level of risk of extinction, while two others (Rhizoprionodon lalandii and Myliobatis goodei) are listed as Data Deficient.
  5. Our results indicate that the commercial exploitation of endemic sharks and rays at risk of extinction is commonplace in southern Brazil. This reinforces the need for more systematic monitoring of the trade in fishery products and more effective application of the environmental legislation and conservation programmes.
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11.
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12.
  1. The use of environmental DNA (eDNA) is a promising approach for the detection of aquatic species, including species at risk. One freshwater mussel species of interest in Atlantic Canada, the brook floater (Alasmidonta varicosa), is listed as being of Special Concern under the Species at Risk Act in Canada and as Vulnerable on the International Union for Conservation of Nature Red List. Further scientific data regarding species distribution and critical habitat is needed for the protection and conservation of this species.
  2. The aim of this study was to design, optimize, and apply a species-specific quantitative polymerase chain reaction assay for the detection of brook floater from eDNA samples, and to assess temporal variability in brook floater eDNA quantities.
  3. Through an eDNA survey performed in New Brunswick rivers in 2017 and 2018, brook floater DNA was found at a total of 16 out of 56 sites sampled. The amount of brook floater DNA detected at all 16 sites was always below the theoretical limit of detection of the assay, and, as such, results were classified as either ‘inconclusive’ or ‘suspected’.
  4. The co-detection of eastern pearlshell (Margaritifera margaritifera), a more abundant freshwater mussel species in Atlantic Canada, was successfully used as a natural positive control.
  5. Temporal variability in the amount of eDNA found in the water was also assessed at a site with a known brook floater population and minimal variability in eDNA quantities was observed from May to September.
  6. These results provide researchers and managers with a new tool for the detection of the brook floater in support of conservation and monitoring efforts.
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13.
  1. One-third of all elasmobranch species currently known to occur in Papua New Guinea are taken as bycatch in the Gulf of Papua trawl fishery. An ecological risk assessment was conducted on the 16 species of sharks and 23 species of rays caught by the fishery.
  2. Eight species were classified to be at low risk, 28 species were at medium risk while three species – Rhynchobatus palpebratus (eyebrow wedgefish), Carcharhinus coatesi (Australian blackspot shark) and Maculabatis astra (blackspotted whipray), all endemic to New Guinea and northern Australia – faced the highest level of risk from the fishery at current fishing levels.
  3. There is potential for more vessels to enter the fishery in future, which is likely to elevate the risk for a greater proportion of elasmobranch species. Ongoing monitoring of bycatch levels, supported by biological and ecological studies on frequently caught species, is required to assess and manage risk in the future.
  4. The development and use of trawl excluder devices or bycatch reduction devices in this fishery have the potential to reduce bycatch levels and reduce risk levels.
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14.
  1. Fisheries monitoring is essential to evaluate and manage fish populations. Effective monitoring is particularly challenging in low- and middle-income countries where fisheries often occur at large spatial scales and include multiple techniques. Recreational spearfishing, for instance, can be detrimental to fish populations and is often underrepresented in management strategies due to the lack of data.
  2. Because recreational fishers frequently share pictures of their catches online, social media can harbour valuable information. As a case study, freely available pictures in social media were used to assess the impacts of spearfishing on the endemic and endangered Brazilian parrotfish, Scarus trispinosus, that has experienced a sharp population decline in recent decades due to overfishing.
  3. It was found that S. trispinosus is widely captured by recreational spearfishing and at larger sizes when compared to artisanal fisheries, revealing complementary fishing pressures operating on different life stages of this species and a lack of compliance to current regulations. The number of users sharing these contents increased between 2007 and 2018, but declined thereafter until 2020.
  4. Identifying where spearfishing is more intense and the most targeted life-stages can inform prioritization of management strategies. Social media can be a rapid and low-cost tool to obtain nationwide fisheries information, especially for recreational fishing activities that have a flawed monitoring.
  5. The public disclosure of ‘trophy fishes’ can reveal lack of compliance to existing regulations and help fill critical information gaps on complementary fishing pressures. This approach may be applicable for many species and types of trophy fishing, providing valuable and useful information for management and conservation.
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15.
  1. This study evaluated the circle hook use as a tool for shark management in the pelagic longline fishery in the Gulf of Gabès.
  2. The usual J‐hook No. 2 with 10° offset, which has been traditionally used by the fishery, was compared to the 18/0 non‐offset circle hook in an alternating fashion along the main line. In total, 22 experimental longline sets were deployed through the shark fishing seasons of 2016 and 2017 to examine the effects of hook types on the catch composition, the catch rates, the hooking location, and the status at haulback.
  3. The catch composition differed significantly among hook types. Moreover, an overall increase in catch rates for the main species, the sandbar shark Carcharhinus plumbeus, and the shortfin mako shark Isurus oxyrinchus, was observed when using circle hooks.
  4. There was no size‐selective effect of circle hooks for the common species. The circle hooks were not effective at reducing at‐haulback mortality of sandbar shark. Conversely, shortfin mako and smooth‐hound shark Mustelus mustelus showed significantly lower relative mortality at haulback with circle hooks than with J‐hooks. Furthermore, circle hooks were more frequently hooked externally than the J‐hooks for the three shark species.
  5. Results demonstrated that the use of 18/0 non‐offset circle hooks in the pelagic shark longline fishery can reduce mortality at haulback for some species without any benefit for the dominant species, the sandbar shark.
  6. Overall, it is difficult to promote the adoption of the use of circle hooks as a management measure in this specialized fishery. Management measures focusing on fishing effort controls, fishing closures in critical habitats, and size limits could have significant benefits for the conservation of shark species and may help to improve the sustainability of the shark fishery in the Gulf of Gabès.
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16.
  1. All seahorse species (genus Hippocampus) are listed under Schedule I of India's Wild Life Protection Act, making all capture and trade of seahorses illegal. In the more than 15 years since the ban, little work has been done to assess its effects on seahorse conservation.
  2. Between 2015 and 2017, fisheries and trade surveys were conducted along the south-east coast of India, in the state of Tamil Nadu, historically known to be a hub for seahorse catches and trade.
  3. Seahorses were primarily landed as bycatch, although in greater quantities by traditional drag nets than as trawl bycatch. Total annual catches were estimated between 4.98 million and 13.64 million seahorses, 87% of which were caught by active non-selective gear.
  4. Generalized additive models revealed that seahorse catch per unit effort had non-linear relations with depth and latitude, and were higher in biogenic habitats, with active, bottom-used, and non-selective gears (e.g. trawls).
  5. The illegal nature of the trade in seahorses hampered an understanding of trade routes and trade volumes. Catch estimates indicated that 11.21–30.31 tonnes of seahorses probably entered trade, yet interviews with traders only documented trade of about 1.6 tonnes.
  6. Fishers reported a decreasing availability of seahorses. Since most seahorses come from bycatch in persistent fisheries that are not directly affected by the ban on seahorse capture, this decline is likely to represent a population decline.
  7. A fishery and trade ban for incidentally caught species, particularly in a poorly regulated fishery, appears to add little conservation value. There needs to be a shift in the management approach, moving from a ban towards spatial and temporal restrictions, and toward enforcing existing fishery regulations.
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17.
  1. Many shark and ray (elasmobranch) species are threatened with extinction, due to overfishing and commercial trade
  2. Sarawak is situated in Malaysian Borneo in the Coral Triangle: a global priority region for elasmobranch conservation. Malaysia is the world’s eighth largest elasmobranch fishing nation, and Sarawak is one of Malaysia’s largest fishing states, yet there are limited species-specific data on catch and trade of elasmobranchs to support conservation and fisheries management decisions.
  3. This study presents landing site and market survey data, collected in Sarawak from January 2017 to December 2019. Geographical, temporal and operational trends in volumes of catch and trade are explored; the total volume, value and species composition of Sarawak's local elasmobranch markets is estimated; and simple size-based indicators are used to assess the sustainability of elasmobranch utilization for several conservation-priority and frequently traded species, including Critically Endangered and CITES-listed scalloped hammerhead sharks (Sphyrna lewini) and bottlenose wedgefish (Rhynchobatus australiae).
  4. The results conservatively estimate that >26,500 elasmobranchs (~90,000 kg) are locally traded in Sarawak annually, worth ~US$125,000 per year at the market level.
  5. Trade is dominated by small to medium-sized coastal requiem sharks (Carcharhinidae) and stingrays (Dasyatidae), with endangered and CITES-listed species making up 26% and 32% of total landings and trade, respectively.
  6. High proportions of immature individuals were recorded, with evidence of overfishing for several species, based on simple size-based indicators.
  7. Several options are outlined for improving management of elasmobranch fishing and trade in the future, including spatio-temporal closures and live release protocols, which could help to reduce the mortality of critically endangered species and implement CITES. Such measures could have large conservation impacts with limited socio-economic cost, since these species make up <5% of the total value of the elasmobranch market. However, management plans need to be co-designed with full participation of affected coastal communities in order to be ethical and effective.
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18.
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19.
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20.
  1. Reef manta rays (Mobula alfredi) are one of the ocean's largest and most charismatic species. Pressure from targeted and bycatch fisheries coupled with their conservative life‐history traits including slow growth, late maturity, and low fecundity has led to catastrophic declines of the global population. The species is now listed as Vulnerable to Extinction on IUCN Red List of Threatened Species.
  2. The global M. alfredi population is widely distributed in highly fragmented subpopulations. The Maldives supports the world's largest known subpopulation that undergoes seasonal migrations which are thought to be linked to peaks in ocean productivity induced by the South Asian Monsoon. Although the species is protected from targeted fisheries in the region, increasing pressures from habitat degradation and unsustainable tourism activities mean their effective conservation relies upon knowledge of the species' habitat use, seasonal distribution, and the environmental influences on such movements.
  3. Photo‐ID sighting records collected between 2005 and 2017 were used to identify key aggregation sites throughout the archipelago, and multiple linear regression and prediction analysis identified the environmental variables affecting variations in the intra‐annual sighting frequency of M. alfredi.
  4. Mobula alfredi were recorded at 273 different sites, 48 of which, with >100 sightings at each, were classified as key areas of habitat use. South‐west monsoon winds and chlorophyll‐a concentration predominantly affected the monthly percentage of M. alfredi sighted on the down‐current side of the atolls.
  5. In a country where climate change and touristic pressure are increasingly threatening this species and its habitat, the identification of key areas of habitat use and temporal changes in the use of these sites highlight the areas that should be prioritized for protection enabling more effective conservation management.
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