3,120 research outputs found
Near-infrared spectroscopy for shark ageing and biology
No full textAccurate and reliable age estimates of sharks are important for informing management that will achieve sustainable outcomes for populations. Age is the foundation of many of the essential parameters, such as growth rate and productivity, that are used in demographic analyses and fisheries assessments (Cailliet et al., 2006; Campana, 2001). Here, "sharks" is used as a general term to refer to sharks, rays, and chimaeras, therwise known as chondrichthyans. Traditionally, to estimate age in sharks, growth bands are counted in their hard parts. Vertebrae or dorsal fin spines are primarily used, although caudal thorns have also been found suitable for ageing in a few species of skates (Cailliet, 2015; Goldman et al., 2012; Serra-Pereira et al., 2008). As sharks age, calcified material accumulates in these structures and can produce visible band pairs that, when formation periodicity has been validated, enable age determination (Goldman et al., 2012; see also Chapter 10 in this volume).
Counting these band pairs requires experience and time to achieve consistent results, and repeated reads are necessary to ensure precision of the counts (Cailliet et al., 2006). It also can require time-consuming preparation, such as sectioning of the structures and enhancement with stains to improve clarity and readability of the band pairs (Irvine et al., 2006b; Matta et al., 2017). In addition, this approach normally requires the lethal removal of the structures used for ageing from an individual. Given the vulnerability of many shark species to exploitation (Dulvy et al., 2014), nonlethal methods for ageing would be beneficial. These issues prompted investigation of near-infrared spectroscopy (NIRS) as a complementary approach to shark ageing. Although NIRS requires traditional band counts of some age structures, it can greatly reduce the time taken to estimate age from a structure and has the potential to be nonlethal (Rigby et al., 2014, 2016b). This chapter reviews how NIRS works and the application and considerations for use of NIRS in shark ageing
Acoustic telemetry
No full textAcoustic telemetry involves the use of sound to convey information relating to the presence of an animal as it moves from one location to another in the aquatic environment. In the context of shark research, this most commonly reflects using acoustic transmitters and receivers to track movement of individuals. Originally, acoustic transmitters simply emitted a pulse that could be detected by a receiving device; researchers followed the sound using a directional hydrophone as the shark swam through the environment and recorded positions every few minutes to represent the movement track of an individual (Holland et al., 1992; Morrissey and Gruber, 1993). As technology developed, information was encoded into acoustic signals by using a series of pings that could be decoded by the receiver. This led to the capacity to provide unique identification codes for an individual tag, which allowed simultaneous tracking of multiple individuals. By combining coded transmitters with data-logging acoustic receivers that could be moored in study sites for long periods, the need for animals to be actively followed was removed. This revolutionized the field of acoustic telemetry by allowing researchers to establish arrays of receivers to detect and track sharks automatically (Heupel et al., 2006). Sensors are also being developed and integrated with transmitters to provide information on the environments that tagged sharks encounter (e.g., depth, temperature) and their behavioral state (e.g., acceleration). Similarly, advances in receiver systems, collaborations, and modes to access stored data provide new ways to examine shark behavior and distribution at broad scales. In this chapter, we discuss the application of acoustic telemetry to track sharks, advances to the technology over time, and the challenges and opportunities this technology has provided to shark research
Social science and its application to the studies of shark biology
No full textMeeting the needs of people while sustaining ecosystems and the benefits they deliver is a global challenge. Coastal marine systems present a particularly important case, given that over half of the world's population lives within 100 km of the ocean, and fisheries provide the primary source of protein for over a billion people worldwide (Leslie et al., 2015). Sharks and rays play important roles in many of these fisheries and coastal communities, as not only do they provide food and income but they can also have strong social and cultural value (Dulvy et al., 2017). However, pressures on sharks and rays from fishing, habitat loss, and other factors are increasing, resulting in global declines in some species and raising concerns that up to a quarter of the world's sharks and rays are threatened with extinction (Dulvy et al., 2008).
At a time when many shark and ray species are experiencing ongoing population declines from these growing pressures, the need to engage in research that bridges the human-shark interface to better inform conservation and fisheries management and policy is becoming increasingly recognized (Jacques, 2010; Simpfendorfer et al., 2011). With the possible exception of work related to "shark attacks" on humans, social science research that focuses on sharks has not kept pace with biophysical science, despite knowledge that understanding people is pivotal to effective natural resource management (Gutierrez et al., 2011; Reid, 2016; Twyman, 2017)
Colin Humphris
No full text"Colin Humphris 2 Sqdrn. RAAF. 1941 - 1942 Author of - 'Trapped on Timor' (as a result of bombing of Darwin Feb. 19, 1942)".Colin Humphris. 2 Squadron, Royal Australian Air Force 1941 - 1942. Author of - 'Trapped on Timor' (as a result of bombing of Darwin February 19, 1942)
Utility of a multi-faceted approach in determining the habitat use of endangered euryhaline elasmobranchs in a remote region of northern Australia
No full textThe overriding aim of this thesis was to explore the habitat use of the critically endangered freshwater sawfish (Pristis microdon) and northern river shark (Glyphis garricki) in the remote Kimberley region of northern Western Australia. This information has been largely lacking and is critical for the management and conservation of these species. Habitat use of these species was documented through the use of long-term catch, environmental and tagging (conventional, acoustic and satellite) data, which was acquired between 2005 and 2009 in the Fitzroy River and King Sound, Western Australia. Monitoring of the various environmental parameters demonstrated that the study area is extremely dynamic, with significant seasonal changes in abiotic variables such as water flow, depth, temperature, turbidity and salinity. Catch data demonstrated that juvenile P. microdon inhabit the Fitzroy River for three to five years, at which time individuals begin to emigrate from the river, prior to maturation. Catch data also demonstrated that juvenile and adult male G. garricki inhabit highly turbid nearshore waters throughout the upper King Sound. Relative abundance of P. microdon in the river varied seasonally and annually, and differed between size classes. A decrease in relative abundance between the early and late dry season, which was only significant with young of the year P. microdon, was attributed to mortality as well as dispersal of individuals. Catches of G. garricki were rare, although this species was relatively abundant in highly turbid waters in King Sound. Foraging, depth use and inter-pool movements of P. microdon in the Fitzroy River were influenced by depth, flow and light intensity/turbidity and potentially by salinity and/or water temperature. However, the response to environmental variables differed between P. microdon size classes, possibly due to differences in trophic and habitat requirements of the various size classes. Results from this study demonstrated that P. microdon is sensitive to environmental change, but appear to endure/recover from short-term (months) negative impacts through behavioural regulation. It is not possible at this time to positively conclude about the impacts of specific environmental changes on G. garricki habitat use, due to the limited data from G. garricki captures and tagging. However, as all G. garricki captured in this study were observed to inhabit tidal creeks and river mouth areas, the destruction of such areas or restriction to and from such areas is likely to negatively impact this species
FIGURE 1 in Range, sexual dimorphism and bilateral asymmetry of rostral tooth counts in the smalltooth sawfish Pristis pectinata Latham (Chondrichthyes: Pristidae) of the southeastern United States
No full textFIGURE 1. Relative frequency of total rostral tooth counts for Pristis pectinata from the southeastern United States (n=105).Published as part of Wiley, Tonya R., Simpfendorfer, Colin A., Faria, Vicente V. & Mcdavitt, Matthew T., 2008, Range, sexual dimorphism and bilateral asymmetry of rostral tooth counts in the smalltooth sawfish Pristis pectinata Latham (Chondrichthyes: Pristidae) of the southeastern United States, pp. 51-59 in Zootaxa 1810 (1) on page 54, DOI: 10.11646/zootaxa.1810.1.3, http://zenodo.org/record/512508
Environmental DNA (eDNA): a valuable tool for ecological inference and management of sharks and their relatives
No full textKnowledge of spatial and temporal variation in abundance is critical for the implementation of effective protective measures for organisms that are both naturally rare and vulnerable to exploitation. The development of management and conservation strategies for elasmobranchs depends on accurate assessment and monitoring of the distribution and abundance of target species in the field, but detecting species occurrences is often even more challenging in the aquatic environment than on land (Webb and Mindel, 2015). Consequently, as is the case for many large, mobile and rare vertebrates, shark detection is inherently difficult.
All organisms continuously leave traces of themselves behind in the environment in the form of shed skin cells, bodily fluids, metabolic waste, gametes, or blood. Any of these materials can contain pieces of the organism's DNA. Environmental DNA (eDNA) analysis is based on the retrieval of this naturally released genetic material from the environment. It generally refers to bulk DNA extracted from an environmental sample such as water but also from soil, sediment, snow, or even from air (Taberlet et al., 2012a). In aquatic systems, macroorganismal-derived eDNA can be present as free DNA, cellular debris, or particle-bound DNA and is mostly present in small fragments, due to rapid degradation (Barnes et al., 2014); however, much of the eDNA is retrieved from cellular material and may therefore contain still relatively undamaged nucleic acid molecules. Nevertheless, eDNA studies focus primarily on the detection of short fragments, as currently available parallel sequencing and qPCR platforms have short-read capabilities limited to a few hundred base pairs. When DNA is present at low concentrations, mitochondrial DNA (mtDNA) is often targeted, as there are substantially more mitochondrial than nuclear DNA copies per cell (Wilcox et al., 2013). Commonly employed mtDNA genes include cytochrome b, cytochrome c oxidase subunit 1 (COI), 12S rRNA, and 16S rRNA (Kelly et al., 2014; Thomsen et al., 2012b; Valentini et al., 2016), and targeted fragments typically fall within the range of 79 to 285 bp (Ficetola et al., 2008; Minamoto et al., 2012). The level of target specificity is often the main determining factor when choosing or designing primers for eDNA analysis
Repeatability of baited remote underwater video station (BRUVS) results within and between seasons
No full text<p>Complete dataset for "Repeatability of baited remote underwater video station (BRUVS) results within and between seasons" in PLoS ONE by: C. Samantha Sherman, Michelle R. Heupel, Mohini Johnson, Muslimin Kaimuddin, L.M. Sjamsul Qamar,Andrew Chin,Colin A. Simpfendorfer.</p>
<p>Abstract [Related Publication]: Baited remote underwater video stations (BRUVS) are increasingly being used to evaluate and monitor reef communities. Many BRUVS studies compare multiple sites sampled at single time points that may differ from the sampling time of another site. As BRUVS use grows in its application to provide data relevant to sustainable management, marine protected area success, and overall reef health, understanding repeatability of sampling results is vital. We examined the repeatability of BRUVS results for the elasmobranch community both within and between seasons and years, and explored environmental factors affecting abundances at two sites in Indonesia. On 956 BRUVS, 1139 elasmobranchs (69% rays, 31% sharks) were observed. We found consistent results in species composition and abundances within a season and across years. However, elasmobranch abundances were significantly higher in the wet season. The elasmobranch community was significantly different between the two sites sampled, one site being more coastal and easily accessed by fishermen. Our results demonstrate that while BRUVS are a reliable and repeatable method for surveying elasmobranchs, care must be taken in the timing of sampling between different regions to ensure that any differences observed are due to inherent differences amongst sampling areas as opposed to seasonal dissimilarities.</p>
<p>The full methodology is available in the Open Access publication from the Related Publications link below.</p>
Demographic Models: life tables, matrix models and rebound potential
No full textInformation on the status of shark populations and how they respond to increases in mortality (e.g. from fishing, predation, disease), is critical to making management decisions about fished or endangered species. It is no surprise then that a considerable part of the fish and fisheries literature is devoted to this type of research. In the ideal situation long-term series of information about a population - catches, fishing effort, change in abundance -exist. In this situation dynamic fishery models can be applied to derive extensive management related information. However, in many situations the data required to support these types of management models do not exist. This is often the case with shark populations, where the collection of these data has been uneconomical or overlooked. In this situation population models that rely primarily on life history parameters can provide some useful information for management. Such models are normally referred to as demographic models. These demographic analyses became popular for shark stocks in the 1990s and are the most widely used form of population model for this group of fishes (Hoenig and Gruber, 1990; Cailliet, 1992; Cortes, 1995, 1998, 1999, 2002; Cortes and Parsons, 1996; Smith, Au and Show, 1998; Simpfendorfer, 1999a,b; Brewster-Geisz and Miller, 2000; Mollet and Cailliet, 2002)
Citizen science in shark and ray research and conservation: strengths, opportunities, considerations and pitfalls
No full textCitizen science programs are growing around the world in number, diversity, and prominence, and they are arguably now accepted as a mainstream scientific methodology (Dickinson et al., 2012; Silvertown, 2009). Modern citizen science programs range from observation-based programs, such as recording local sightings of specific species or phenomena, to global efforts to collect "big data," such as the National Aeronautics and Space Administration (NASA) program Global Learning and Observations to Benefit the Environment (GLOBE), where citizen scientists from around the world use a smartphone app to photograph clouds and record data on mosquitoes. In the fields of biology and ecology, citizen scientists are collecting data on changes in species distributions, pollution, invasive species, threatened species, disease, phenology, biodiversity, habitats, and landscapes and are making tangible conservation contributions (Bonney et al., 2009, 2014; Dickinson et al., 2010; Edgar et al., 2017; Robinson et al., 2015; Silvertown, 2009). In situations where citizen science participants are numerous and widely distributed, these initiatives can help professional scientists greatly expand their spatial and temporal sampling capability, and thus the scope and scale of research questions they can address. In terms of biodiversity monitoring alone, citizen science programs have been estimated to include 1.5 million volunteers that contribute over $2.5 billion worth of in-kind contributions to biodiversity science every year (Theobald et al., 2015)
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