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Effective management of critically endangered sawfishes can be a difficult task, in part due to interspecies misidentification. Current methods for identifying sawfishes can be impractical as they are based on morphological features that are often unobservable. Further exploration is required to develop a more reliable means of identification.This study explored the utility of sawfish rostra in determining the species, size and sex of sawfishes, as rostra are commonly the only feature of a sawfish observed by fishers or present in public and private collections.A morphometric and meristic database consisting of over 1100 narrow sawfish (Anoxypristis cuspidata), dwarf sawfish (Pristis clavata), largetooth (or freshwater) sawfish (Pristis pristis; formerly Pristis microdon) and green sawfish (Pristis zijsron) rostra from Australian waters, was statistically analysed.Identification of sawfishes was found to be possible through the use of the variables: inter‐tooth spacing, standard rostrum width/standard rostrum length, standard rostrum length/total rostrum length, rostrum tip width/standard rostrum length, and/or rostral tooth count range, although the distinguishing variables were species‐dependent.The relationship between standard rostrum length and total length was also observed to vary substantially between most species. Models for estimating total length from standard rostrum length are provided.This study has provided a tool that can be used to identify accurately the species and size of sawfishes by their rostra, and therefore can assist in clarifying historical and contemporary sawfish records, nomenclature and distributions. A better understanding of these issues should allow sawfish conservation strategies to become more focused, and thus more effective. Copyright © 2013 John Wiley & Sons, Ltd.

BackgroundAs apex and mesopredators, elasmobranchs play a crucial role in maintaining ecosystem function and balance in marine systems. Elasmobranch populations worldwide are in decline as a result of exploitation via direct and indirect fisheries mortalities and habitat degradation; however, a lack of information on distribution, abundance, and population biology for most species hinders their effective management. Environmental DNA analysis has emerged as a cost‐effective and non‐invasive technique to fill some of these data gaps, but often requires the development of species‐specific methodologies.AimsHere, we established eDNA methodology appropriate for targeted species detections of Bull Sharks, Carcharhinus leucas, in estuarine waters in the northern Gulf of Mexico.Materials and MethodsWe compared different QIAGEN®DNeasy® extraction kit protocols and developed a species‐specific Droplet Digital™ PCR (ddPCR) assay by designing primers and an internal probe to amplify a 237 base pair portion of the ND2 gene in the mitochondrial genome of C. leucas. To validate the developed methods, water samples were collected from known C. leucas habitat and from an ex situ closed environment containing a single C. leucas individual. The effectiveness of the assay in an open environment was then assessed by placing one C. leucas into a flow‐through mesocosm system and water samples were collected every 30 min for 3 hr.ResultsThe developed C. leucas ‐specific assay has the ability to detect target DNA concentrations in a reaction as low as 0.6 copies/μl. DdPCR reactions performed on water samples from known habitat and 30 min after a shark was added to the closed environment contained 1.62 copies/μl and 166.6 copies/μl of target C. leucas eDNA, respectively. Carcharhinus leucas eDNA was detected in the flow‐through system within 30 min, but concentrations remained low and variable throughout the duration of the experiment.

Understanding the population structure of a species and the barriers that disrupt dispersal is important to accurately assess the global conservation status and manage the risk of local extinction. This is especially true for species of commercial importance (Begg et al., 1999) or conservation concern (Moritz, 1994), which are impacted disproportionally by anthropogenic or environmental pressures. Dispersal

The Critically Endangered Smalltooth Sawfish, Pristis pectinata, was once widespread in the tropical and subtropical waters of the Atlantic Ocean, but following substantial declines over the past century, the core population is currently confined to southwest Florida in the U.S. and the Bahamas. Recent research and verified public encounter reports suggests that this core population may be stabilizing and, potentially, expanding into formerly occupied areas of their historic range in the Western Atlantic; however, the status of this species in noncore waters is not well understood. Environmental DNA (eDNA) methods provide a relatively cost effective and rapid assessment tool for monitoring species occurrence in aquatic habitats. Here, we have developed an eDNA tool: a species-specific Droplet Digital™ PCR (ddPCR™) assay targeting a 100-base pair portion of the mitochondrial NADH dehydrogenase subunit 2 gene in P. pectinata, with the ability to reliably detect as little as 0.25 pg of target DNA. The assay was validated by collecting and analyzing a water sample from known P. pectinata nursery habitat in Florida, which was found to contain an average of 11.54 copies of target DNA/µL (SE = 0.72) in the reaction. The assay was then further tested by placing a juvenile sawfish in an ex situ tank and analyzing water samples collected at time intervals. The implementation of this eDNA tool into field surveys will provide additional, reliable data to assess species recovery and aid in prioritizing localities beyond the core range in which to focus research and education initiatives.

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This research demonstrates how population structure differs in elasmobranchs with different patterns of habitat use. Population structure was assessed using data at microsatellite loci in three species of Pristis sawfishes in northern Australian waters. Statistically significant population structure was found in each of P. clavata (FST = 0.021, F′ST = 0.151, P < 0.001) and P. zijsron (FST = 0.026, F′ST = 0.130, P < 0.001), which spend their entire life in marine waters. In contrast, there was no evidence of significant population structure in P. pristis, which uses freshwater rivers as juveniles and marine waters as adults (FST = 0.004, F′ST = 0.029, P = 0.210). When combined with the results of mtDNA analyses from a previous study, the results suggested that dispersal in P. pristis is male-biased, whereas both male and female gene flow are restricted at large spatial scales in each of P. clavata and P. zijsron in Australian waters. The present study has provided the first evidence of sex-biased dispersal in a sawfish.