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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. 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. [ABSTRACT FROM AUTHOR]

Understanding movement patterns underlies effective management and conservation measures. The current study summarises the main findings from a tagging program of Western Australian sharks to provide insights into the movement patterns of the main commercial shark species: dusky (Carcharhinus obscurus), sandbar (C. plumbeus), gummy (Mustelus antarcticus) and whiskery (Furgaleus macki) sharks. Between 1993 and 2020, >12 000 individuals from 52 taxonomic groups were implanted with conventional tags in Western Australia, of which 8.5% were recaptured. Most of the tagged (74.5%) and recaptured (95.8%) individuals belong to the four main commercial shark species. Recaptured individuals of these species, as well as tiger (Galeocerdo cuvier) and bronze whaler (C. brachyurus) sharks showed displacements of >1000 km and rates of movement (ROMs) of >10 km day–1, with the exception of whiskery sharks, which showed much slower ROMs (<3 km day–1). Despite tagged dusky and sandbar sharks being predominately small individuals and gummy and whiskery sharks being large individuals, dusky and sandbar sharks had faster ROMs and a greater proportion of recaptures outside the release zone. Our study provided the information required for estimating movement rates across different fishing zones and therefore defining the spatial scale for managing these shark species. The study of shark movement has attracted considerable attention over the past decades. Conventional tagging remains a cost-effective approach for studying shark life history. The current study has provided evidence of the contrasting movement of sharks on the basis of almost three decades of tagging efforts distributed across Western Australia, where >12 000 sharks and rays have been tagged to date. Our study identified differences in relative movement patterns of Western Australian sharks and showed that valuable movement information can be obtained from conventional tagging. [ABSTRACT FROM AUTHOR]

Sawfish (Pristidae) are considered to be among the most threatened families of elasmobranch (sharks and rays). There is a need to gather information on the status of poorly known sawfish populations to assist in global recovery initiatives.This study used interviews with local fishers to investigate the presence of sawfish in southern Papua New Guinea (PNG) and their interactions with and uses and values for small‐scale fishers.A range of sawfish size classes are still encountered throughout southern PNG, while juvenile largetooth sawfish Pristis pristis were additionally reported in the freshwater reaches of all rivers surveyed. Reports of large size classes in estuarine and marine environments provide an optimistic outlook that sawfish populations persist throughout southern PNG.Most fishers that catch sawfish retain them for various uses including consumption and for the sale of meat, fins and occasionally rostra. Negative population trends including decreases in catch frequency and/or size classes were reported by 66% of interviewees, with the largest declines being reported in the Kikori River. The increasing technical capacity of small‐scale fishers, their preference for gillnetting and the emerging market for teleost swim bladder (a high‐value fishery product) present a major ongoing threat to sawfish in southern PNG. Furthermore, the tendency of fishers to kill or remove rostra from entangled sawfish results in high fishing mortality regardless of any use by the fisher.This study indicates that considerable community engagement will be necessary to manifest any legislative actions or increased enforcement on international trade regulations for sawfish in PNG. This is due to traditional land and waterway ownership values throughout PNG and the local perception of sawfish as a traditional food resource rather than an animal of intrinsic biodiversity value as perceived by global conservationists. Future research should consider exploring culturally appropriate conservation initiatives that are likely to achieve engagement and participation from local fishers. [ABSTRACT FROM AUTHOR]

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The silky shark (Carcharhinus falciformis) is one of the most heavily fished tropical shark species globally, and currently there is increasing concern for its conservation status. However, large differences and ambiguity in life history parameter estimates among regions complicates its conservation and fisheries management. Using a Leslie matrix model that incorporated stochastic effects, we analysed the intraspecific demography of C. falciformis using available life history data from seven regions. Among regions, large differences were observed in generation time and age-specific reproductive contributions. Carcharhinus falciformis generally had low resilience to fishing mortality (F) throughout its distribution. Age-at-first-capture and age-at-last-capture management approaches resulted in substantial differences among regions. This was largely influenced by age-at-maturity. However, in scrutinizing some regional life history studies, it is likely that sampling design and methodological differences among regions have resulted in inaccuracies in life history parameter estimates and subsequent demographic attributes. This implies that age and life-stage-dependent management approaches using these possibly inaccurate life history parameters may be inappropriate. We suggest that a greater emphasis needs to be placed on eliminating human sources of error in elasmobranch life history studies to ensure management for wide-ranging species, such as C. falciformis , is most effective. [ABSTRACT FROM AUTHOR]

Abstract: Leslie matrix models are an important analysis tool in conservation biology that are applied to a diversity of taxa. The standard approach estimates the finite rate of population growth (λ) from a set of vital rates. In some instances, an estimate of λ is available, but the vital rates are poorly understood and can be solved for using an inverse matrix approach. However, these approaches are rarely attempted due to prerequisites of information on the structure of age or stage classes. This study addressed this issue by using a combination of Monte Carlo simulations and the sample‐importance‐resampling (SIR) algorithm to solve the inverse matrix problem without data on population structure. This approach was applied to the grey reef shark (Carcharhinus amblyrhynchos) from the Great Barrier Reef (GBR) in Australia to determine the demography of this population. Additionally, these outputs were applied to another heavily fished population from Papua New Guinea (PNG) that requires estimates of λ for fisheries management. The SIR analysis determined that natural mortality (M) and total mortality (Z) based on indirect methods have previously been overestimated for C. amblyrhynchos, leading to an underestimated λ. Updated distributions of Z and λ were produced for the GBR population and corrected obvious error in the demographic parameters for the PNG population. This approach provides opportunity for the inverse matrix approach to be applied more broadly to situations where information on population structure is lacking. [ABSTRACT FROM AUTHOR]

Acoustic telemetry is used to investigate a diverse suite of questions regarding the biology and ecology of a range of aquatic species, and is an important tool for fisheries and conversation management. Herein we present a brief review of the Australian acoustic telemetry literature in the context of key areas of progress, drawing from several recent studies and identifying areas for future progress. Acoustic telemetry has been increasingly used in Australia over the past decade. This has included substantial investment in a national acoustic array and the associated development of a national acoustic telemetry database that enables tag deployment and detection data to be shared among researchers (the Integrated Marine Observing System Animal Tracking Facility). Acoustic telemetry has contributed to important areas of management, including public safety, design and management of marine protected areas, the use of closures in fisheries management, informing environmental flow regimes and the impacts of fisheries enhancements, and is most powerful when used as a complementary tool. However, individual variability in movement often confounds our ability to draw general conclusions when attempting to characterise broad-scale patterns, and more work is required to address this issue. This overview provides insight into the important role that acoustic telemetry plays in the research and management of Australian aquatic ecosystems. Application of the technology transcends aquatic environments and bureaucracies, and the patterns revealed are relevant to many of the contemporary challenges facing decision makers with oversight of aquatic populations or ecosystems. [ABSTRACT FROM AUTHOR]

Coastal sharks face increasing pressure from anthropogenic impacts and environmental change. Estimated population declines in some species have created uncertainty about the effectiveness of existing management approaches. In particular, there are scarce data on the benefits of marine protected areas (MPAs) for sharks, including whether they can be used to conserve multiple sympatric species comprising diverse life histories and habitat use patterns., This study used fishery-independent longline and gill-net surveys to investigate the effects of sub-bay-sized MPAs ( c. 100-300 km2) on the abundance and community structure of tropical coastal sharks. In addition, tag-recapture data from fishery-dependent and fishery-independent sources were used to investigate the movements of individuals across MPA boundaries., Species composition varied significantly between management zones, and overall shark abundance on longlines was higher inside MPAs., Length-frequency distributions of blacktip ( Carcharhinus tilstoni/Carcharhinus limbatus) and pigeye ( Carcharhinus amboinensis) sharks inside MPAs included a greater proportion of sharks larger than c. 800 mm compared with those in open zones, although results varied between gear types for pigeye sharks., Tagging and recapture locations indicated repeated and potentially long-term use of MPAs by individuals of some species., Although the potential benefits of MPAs were not equal for all species, coastal MPAs may increase the survival of young sharks to maturity, or shelter parts of breeding stocks, and therefore do not necessarily need to be large to provide benefits., Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Understanding the efficacy of marine protected areas (MPAs) for wide-ranging predators is essential to designing effective management and conservation approaches. The use of acoustic monitoring and network analysis can improve our understanding of the spatial ecology and functional connectivity of reef-associated species, providing a useful approach for reef-based conservation planning. This study compared and contrasted the movement and connectivity of sharks with different degrees of reef association. We examined the residency, dispersal, degree of reef connectivity, and MPA use of grey reef (Carcharhinus amblyrhynchos), silvertip (C. albimarginatus), and bull (C. leucas) sharks monitored in the central Great Barrier Reef (GBR). An array of 56 acoustic receivers was used to monitor shark movements on 17 semi-isolated reefs. Carcharhinus amblyrhynchos and C. albimarginatus were detected most days at or near their tagging reef. However, while C. amblyrhynchos spent 80% of monitoring days in the array, C. albimarginatus was only detected 50% of the time. Despite both species moving similar distances (<50 km), a large portion of the population of C. albimarginatus (71%) was detected on multiple reefs and moved more frequently between reefs and management zones than C. amblyrhynchos. Carcharhinus leucas was detected less than 20% of the time within the tagging array, and 42% of the population undertook long-range migrations to other arrays in the GBR. Networks derived for C. leucas were larger and more complex than those for C. amblyrhynchos and C. albimarginatus. Our findings suggest that protecting specific reefs based on prior knowledge (e.g., healthier reefs with high fish biomass) and increasing the level of protection to include nearby, closely spaced reef habitats (,20 km) may perform better for species like C. albimarginatus than having either a single or a network of isolated MPAs. This design would also provide protection for larger male C. amblyrhynchos, which tend to disperse more and use larger areas than females. For wide-ranging sharks like C. leucas, a combination of spatial planning and other alternative measures is critical. Our findings demonstrate that acoustic monitoring can serve as a useful platform for designing more effective MPA networks for reef predators displaying a range of movement patterns. [ABSTRACT FROM AUTHOR]

Determining the recovery potential of endangered species is an important component for developing strategies necessary to return populations to healthy levels. Many species of endangered marine animals have been regarded as having low productivity and therefore, an inherent inability to rapidly recover from severe depletion., An age-structured Leslie matrix model was constructed for the US population of smalltooth sawfish, Pristis pectinata, to determine their ability to recover under scenarios using different life history inputs and the effects of bycatch mortality and catastrophes., Population growth was highest ( λ=1.237 yr-1) when age-at-maturity was 7 yr and decreased to 1.150 yr-1 when age-at-maturity was 11 yr., Despite a high level of variability throughout the model runs, in the absence of fishing mortality or climate catastrophic effects the population grew at a relatively rapid rate approaching carrying capacity in 40 or 50 yr when the initial population was 600 or 2250 females, respectively. Population projections under various levels of fishing mortality resulted in extinction when mortality was highest, initial population size was small, and age-at-maturity was 11 yr. Scenarios testing the potential effects of extreme cold exposure showed little difference to those scenarios testing the effects of fishing mortality., Using the optimistic estimates of population size, lower age-at-maturity and the lower level of fisheries-related mortality, smalltooth sawfish in US waters appear to have the ability to recover within the foreseeable future. Effective management and recovery of this species can only be achieved by keeping fishing-related mortality low., Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Concern over declining shark populations has led to an intense interest in their conservation and management. Due to the difficulties involved in managing adult sharks, focus has been placed on young juvenile and neonate age classes that inhabit discrete inshore nursery areas. However, past confusion over what qualifies as a nursery habitat has led to the identification of vast coastal areas as nurseries, making conservation unfeasible. With the establishment of more discerning criteria for nursery area identification such concerns have been somewhat alleviated, but while effort has been put into defining, identifying, mapping, and in some cases protecting nursery areas, little attention has been paid to the practical value of nurseries for the recovery of exploited shark populations. Often neonate and young juveniles are considered the most critical age classes in terms of population stability/recovery, but evidence is mounting that suggests life stages outside the nursery may be more important in this regard. While nursery area protection should remain a component in shark management strategies it will be critical to link early life stage conservation with management strategies that encompass older individuals residing outside nurseries if effective management is to be achieved. [ABSTRACT FROM AUTHOR]

Acoustic telemetry (AT) is a rapidly evolving technique used to track the movements of aquatic animals. As the capacity of AT research expands it is important to optimize its relevance to management while still pursuing key ecological questions. A global review of AT literature revealed region-specific research priorities underscoring the breadth of how AT is applied, but collectively demonstrated a lack of management-driven objectives, particularly relating to fisheries, climate change, and protection of species. In addition to the need for more research with direct pertinence to management, AT research should prioritize ongoing efforts to create collaborative opportunities, establish long-term and ecosystem-based monitoring, and utilize technological advancements to bolster aquatic policy and ecological understanding worldwide. Animal tracking provides integral spatiotemporal information that contributes to the growing field of movement ecology. AT is one of the main approaches to track the movements of aquatic animals. The proliferation of AT research and technological innovation have increased the ability to explore ecological and management-related questions. Effective integration of AT data at relevant scales to inform management is still limited by a disconnect between management goals and research objectives, as well as global challenges such as equipment compatibility. A comprehensive global overview of existing AT research identifying the knowledge gaps across regions of the world is necessary to ensure that future research advances aquatic animal science and governance. [ABSTRACT FROM AUTHOR]