Reproductive philopatry in bull sharks Carcharhinus leucas was investigated by comparing mitochondrial (NADH dehydrogenase subunit 4, 797 base pairs and control region genes 837 base pairs) and nuclear (three microsatellite loci) DNA of juveniles sampled from 13 river systems across northern Australia. High mitochondrial and low microsatellite genetic diversity among juveniles sampled from different rivers (mitochondrial φ(ST) = 0·0767, P < 0·05; microsatellite F(ST) = -0·0022, P > 0·05) supported female reproductive philopatry. Genetic structure was not further influenced by geographic distance (P > 0·05) or long-shore barriers to movement (P > 0·05). Additionally, results suggest that C. leucas in northern Australia has a long-term effective population size of 11 000-13 000 females and has undergone population bottlenecks and expansions that coincide with the timing of the last ice-ages.

We compare vertebral microchemistry with previously described age-related movement patterns of bull sharks Carcharhinus leucas and pig-eye sharks C. amboinensis within coastal waters of north Australia. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) quantified the chemical signatures of nursery habitats within the vertebrae of juvenile and adult sharks. We examined evidence for adults returning to these habitats by applying LA-ICP-MS along a growth axis of their vertebrae. We transposed chemical signatures with growth increments in adult vertebrae to correlate with age estimates. Unique elemental signatures were identified in each of the freshwater nurseries, but we did not find them in adult vertebrae. Age-specific changes in vertebral microchemistry in mature female bull sharks correlate with periodic returns every 1 to 2 yr to less saline environments to pup. We were unable to discriminate among natal habitats of pig-eye sharks using elemental fingerprints, and age-specific changes in vertebral microchemistry were also absent. We conclude that changes in vertebral microchemistry correlate with known habitat use patterns of the bull and pig-eye sharks, showing the potential of vertebral microchemistry to discern movement patterns in sharks. KEY WORDS: Vertebral microchemistry · LA-ICP-MS · Movement · Long-term · Resource partitioning · CarcharhinidaeResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 434: 133-142, 2011 Speed et al. 2010) that are critical to the maintenance of genetic diversity and replenishment of populations (Hueter et al. 2005).Studies tracking shark movements and identifying patterns of habitat use in coastal regions typically involve tagging with standard (numerical), satellite or sonar tags (Speed et al. 2010). Such an approach is often logistically difficult and expensive because it first involves the capture, tagging and release (in good condition) of the shark. Furthermore, the animals must either be recaptured (standard tags), or tags must report to satellites or arrays of listening stations (sonar tags) for data acquisition (Voegeli et al. 2001, Simpfendorfer & Heupel 2004. Rates of recapture are usually low, while failure of expensive satellite tags to report is commonplace (Hays et al. 2007). Arrays of listening stations require considerable effort to deploy, download and maintain, which can limit the duration and spatial extent of a study using this approach. Despite these problems, studies using these techniques have mapped fine-scale (25 km) movements of different-age cohorts of sharks in shallow coastal waters (Simpfendorfer et al. 2005, Yeiser et al. 2008, Heithaus et al. 2009, Ortega et al. 2009, but the logistics, cost and limited life span of tags have restricted the number of target individuals and species and, in the case of sonar tags, the spatial extent of the sampling area.To overcome the limitations associated with conventional tracking, natural chemical fingerprints are a developing ...

The freshwater sawfish (Pristis microdon) is a critically endangered elasmobranch. Ontogenetic changes in the habitat use of juvenile P. microdon were studied using acoustic tracking in the Fitzroy River, Western Australia. Habitat partitioning was significant between 0+ (2007 year class) and larger 1+ (2006 year class) P. microdon. Smaller 0+ fish generally occupied shallower water (<0.6 m) compared with 1+ individuals, which mainly occurred in depths >0.6 m. Significant differences in hourly depth use were also revealed. The depth that 1+ P. microdon occupied was significantly influenced by lunar phase with these animals utilising a shallower and narrower depth range during the full moon compared with the new moon. This was not observed in 0+ individuals. Habitat partitioning was likely to be related to predator avoidance, foraging behaviours, and temperature and/or light regimes. The occurrence of 1+ P. microdon in deeper water may also result from a need for greater depths in which to manoeuvre. The present study demonstrates the utility of acoustic telemetry in monitoring P. microdon in a riverine environment. These results demonstrate the need to consider the habitat requirements of different P. microdon cohorts in the strategic planning of natural resources and will aid in the development of management strategies for this species.

The Freshwater Sawfish Pristis microdon was captured in marine waters of King Sound, and estuarine and fresh waters of the Fitzroy and Robinson rivers, in the Kimberley region of Western Australia. In light of the IUCN listing of the species as critically endangered, non-destructive means, including tagging-recapture data and information from specimens found dead on the banks, were utilised. Observations of sexual maturity, annuli present on vertebrae, recaptures of tagged individuals and length-frequency data suggested that the freshwaters of the Fitzroy River are a nursery for this species where immature individuals (up to 2800 mm total length) remain for a maximum of four or five years. Morphology and counts of the number of rostral teeth indicated that, in most cases, the rostral tooth morphology can be used to differentiate male and female P. microdon and also are useful in distinguishing this species from the congeneric and sympatric Pristis clavata. Furthermore, differences in the relationship between rostrum length and total length between the sexes may provide an effective diagnostic tool for the collation of historical distribution and sex ratio data from rostrums held in private collections. Rostral tooth counts and length at age data also suggest that the synonymisation of P. microdon, Pristis zephyreus and Pristis perotteti is not warranted.

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.