Karissa Lear

Although the red fox (Vulpes vulpes) is considered one of the most damaging and adaptive invasive carnivorous mammals that consumes a wide variety of vertebrate and invertebrate taxa, there are surprisingly few reports of red foxes hunting fish. We observed evidence of an attempted predation event by a red fox on a neonate green sawfish (Pristis zijsron) within a deltaic island in the Ashburton River estuary, a remote desert river in Western Australia. The site is a globally important nursery where newborn sawfish arrive annually in spring. Injuries to the sawfish included paw/claw marks on the head, damage to the rostrum, which is a formidable tool that is used for both defence against predators and for detecting and attacking prey, as well as a major hole in the head and damage to the gills, which are vital for respiration, osmoregulation, nitrogenous waste excretion, pH regulation, and hormone production. A series of tracks suggests at least one fox parades the shallow tidally influenced banks, with evidence of a green mud crab (Scylla serrata) having also been predated on. There have also been reports of red fox predation of sea turtle nests nearby. This is the first record of a red fox hunting in marine waters and one of the few identifying fish as prey. We suggest that a monitoring program for foxes, and possibly a control program, is warranted prior to the annual seasonal colonisation of this habitat by neonate green sawfish and nesting turtles, which may in turn reduce predation of sympatric species.

The scalloped hammerhead Sphyrna lewini and the great hammerhead S. mokarran are large, coastal to semi-oceanic shark species common to waters of the US east coast where they are regularly taken in commercial and recreational fisheries, particularly the bottom longline fishery. High rates of hooking mortality and low rates of population growth are believed to have caused severe declines in the US Atlantic populations of these species. The objective of this study was to determine the physiological stress induced by bottom longline capture in both S. lewini and S. mokarran. Physiological stress was quantified using the blood biochemical indicators glucose, lactate, pH, haematocrit, sodium, potassium, calcium, chloride and magnesium, which have been demonstrated to indicate physiological stress in elasmobranchs. Each shark captured was assigned a condition factor, which was compared with the stress parameters and time on hook to quantify stress induced by different longline hook times. In S. lewini, the physiological stress parameters lactate, pH, sodium and chloride scaled with hook time, whereas in S. mokarran, only lactate was affected by hook time. In both species, water temperature affected lactate and glucose levels, as well as sodium and pH levels in S. lewini and magnesium levels in S. mokarran. These data will be useful for estimating post-release mortality of S. lewini and S. mokarran from measurements taken at the time of capture, and quantifying the physiological stress response to longline capture in both species to the Atlantic bottom longline fishery.

For globally threatened species, patchy data pose challenges in both establishing historical baselines and assessing current distributions. In the case of saw-fishes, much previous research has relied on amputated trophy rostra or historical photographs to fill data gaps in distribution and population estimates. However, the established morphometric models that allow the estimation of total length from rostra are restricted by the data available to generate them, with many constructed solely from juvenile morphometric data, and robust error testing rarely performed. This study generates an independent dataset from citizen science photographs and field measurements, incorporating sawfishes of all life history stages, to test the robustness of previously proposed models for the four Indo-Pacific sawfish species. Rostrum-to-length morphometric models (RLMs) were confirmed for Pristis clavata and Pristis pristis, and a new model was proposed for Pristis zijsron. A key source of error in previous RLMs for Anoxypristis cuspidata was identified as changing rostrum morphology with body size, but there were insufficient measurements in the present dataset to propose a new robust model for this species. This study highlights the problems associated with extrapolating total lengths of animals beyond the size bounds used to produce the original model. For historically exploited species like sawfishes, which are often represented in collections by trophies alone, these methods outline a critical step prior to use in further ecological study.

Context In this study, single-nucleotide polymorphisms (SNPs) were used to investigate kinship for the green sawfish (Pristis zijsron). Aims To examine the relatedness of P. zijsron across an expansive coastline in Western Australia. Methods Sampling was conducted between the Fitzroy River estuary and Bay of Rest in the eastern Indian Ocean (north-western Australia) between 2003 and 2022. SNPs were generated from tissues collected from 137 live and 1 recently deceased P. zijsron. Key results Overall, 62 individual P. zijsron were assigned to 25 litters of full siblings, with litter sizes ranging from 2 to 5 pups, and 76 P. zijsron individuals were assigned to 96 half sibling pairwise relationships. Four pairs of half siblings were captured more than 500 km and born at least 6 years apart, including one pair of neonates captured ~870 km and 8 years apart, in the Ashburton River estuary (Pilbara) and Cable Beach (Broome). Furthermore, a pair of full-sibling pups (i.e. young of the year) caught at Cape Keraudren (Pilbara) in 2008 were half siblings of a pup caught in the Ashburton River in 2014. Conclusions This study provides evidence of long-distance, likely parental, movement of P. zijsron. Implications Dispersal of P. zijsron over large spatial scales indicates that populations could be replenished from elsewhere should they experience a decline, thereby reducing the risk of localised extinction for this species.

Although human-made barriers to animal movement are ubiquitous across many types of ecosystems, the science behind these barriers and how to ameliorate their effects lags far behind in marine environments compared with terrestrial and freshwater realms. Using juvenile sawfish in an Australian nursery habitat as a model system, we aimed to assess the effects of a major anthropogenic development on the movement behavior of coastal species. We compared catch rates and movement behavior (via acoustic telemetry) of juvenile green sawfish (Pristis zijsron) before and after a major coastal structure was built in an important nursery habitat. Acoustic tracking and catch data showed that the development did not affect levels of sawfish recruitment in the nursery, but it did constrain movements of juveniles moving throughout the nursery, demonstrating the reluctance of shoreline-associated species to travel around large or unfamiliar coastal structures. Given the current lack of information on human-made movement barriers in the marine environment, these findings highlight the need for further research in this area, and we propose the development of and experimentation with marine animal crossings as an important area of emerging research.

In this study, single nucleotide polymorphisms (SNPs) were used to investigate kinship, genetic diversity and inbreeding within a globally significant area for the Critically Endangered giant shovelnose ray, Glaucostegus typus (Anonymous [Bennett] 1830). Sampling for G. typus was conducted in the eastern Indian Ocean, along an expansive (~ 1000 km) stretch of the Western Australian coastline. Single-read sequencing was performed using a Glaucostegus DArTseq™ platform, with a high-density assay of 2.5 million sequence reads. Kinship, genetic diversity and inbreeding were investigated for G. typus using between 564 and 4126 SNPs. Four full and four half sibling dyads were detected amongst 90 genotyped G. typus, including one pair of half siblings separated by > 600 km of coastline, providing evidence of long-distance, likely parental, movement. Observed heterozygosity (HO = 0.29–0.30) and gene diversity (HS = 0.32–0.33) were relatively low compared to other rays, although a lack of previous studies using SNP data may reduce the effectiveness of comparisons. Moderate levels of inbreeding were detected at each site (FIS = 0.07–0.13) and across all sites, combined (FIS = 0.09). Long-distance movement of G. typus between sampled assemblages reduces the risk of localised extinctions across the study area; additional work is required to determine whether the sampled assemblages are genetically distinct from one another, as well as other G. typus populations throughout its Indo-West Pacific range.

Purpose
This study examined the metazoan ectoparasites of the Critically Endangered giant shovelnose ray, Glaucostegus typus, in the eastern Indian Ocean.

Methods
We screened 186 G. typus for ectoparasites in four coastal regions of Western Australia between 2020 and 2022: the Pilbara Region, Exmouth Gulf, Ningaloo Coast and Shark Bay.

Results
Five parasite taxa were encountered on 186 G. typus: Caligus furcisetifer (Copepoda: Caligidae), Dermopristis cairae (Monopisthocotyla: Microbothriidae), Branchellion plicobranchus and Stibarobdella macrothela (Hirudinida: Piscicolidae), and praniza larvae of unidentified gnathiid isopod/s (Isopoda: Gnathiidae). Two of these species, B. plicobranchus and S. macrothela, are reported for the first time on G. typus. Only C. furcisetifer and S. macrothela were relatively common, encountered on 31% and 40% of G. typus, respectively. Gnathiids were observed infrequently, encountered on 13% of G. typus, and D. cairae and B. plicobranchus were scarce, encountered on 1% and 2% of G. typus, respectively. Intensity of infection for C. furcisetifer and gnathiids increased with host length. Likelihood of infection varied seasonally for C. furcisetifer, being considerably lower in summer, and regionally for gnathiids, being greatest at Shark Bay. Intensity and likelihood of infection for S. macrothela increased with host length and varied regionally, being greatest at Shark Bay.

Conclusion
These findings improve our understanding of the downstream impacts for dependent parasites that might arise should populations of G. typus continue to decline.

In this study, single nucleotide polymorphisms were used to investigate kinship and philopatry for the Critically Endangered green sawfish, Pristis zijsron, in Western Australia.

Sampling was conducted in an important nursery area: the Ashburton River estuary and adjacent tidal creeks. Kinship was inferred from the genotypes of 104 sawfish sampled between 2011 and 2014 (n = 31), and 2020 and 2022 (n = 73).

The total number of dams contributing across all sites and time periods was estimated to be between 50 and 56.

Fifty‐two full sibling dyads, 90 half sibling dyads and 72 third‐degree dyads were detected, involving 58, 67, and 46 P. zijsron, respectively. Of these, 34 half sibling dyads were related maternally and 56 related paternally, including multiple maternal and paternal half siblings pupped in different years, suggesting both female and male philopatry. Catch data indicated that two groups of maternal half siblings were littermates, demonstrating multiple paternity. A high degree of relatedness was found across the study area, with 88% of P. zijsron related to at least one other individual up to the third‐degree.

Evidence for female philopatry in P. zijsron highlights the importance of protecting nursery areas for this species. The occurrence of philopatric behaviour in male and female P. zijsron suggests that dispersal might be limited in both sexes of this species, highlighting the need to investigate the amount of genetic diversity and incidence of inbreeding within remaining populations.

Wedgefishes have recently been recognised as one of the most imperilled marine fish families worldwide. However, many knowledge gaps about their biology and ecology hinder conservation efforts. Here we used a combination of acoustic telemetry and acceleration datalogger technology to gain fundamental insights into the fine-scale behaviour, habitat use, size of activity spaces, and residency of adult female bottlenose wedgefish (Rhynchobatus australiae) in the Ningaloo region of northwestern Australia. Acoustic tracking data over one year demonstrated that female bottlenose wedgefish continuously resided in a relatively small area of a productive coral reef lagoon. Acceleration data revealed that bottlenose wedgefish were nocturnal, with time of day having a greater influence on activity than tidal patterns. Bottlenose wedgefish also increased activity with seasonally increasing temperatures. We identified several discrete behavioural signatures in the acceleration data, inferred to correspond to chafing, settling/burying behaviour, foraging behaviour, and escape behaviour, based on their kinematics. Further observations are required to confirm these behaviours with certainty. Additionally, according to datalogger and acoustic data, tagged bottlenose wedgefish rarely inhabited areas greater than 2 m deep. Together, these first insights into behaviour and habitat use of adult female bottlenose wedgefish highlight the importance of nearshore habitats for this species and indicate that they may be highly resident to specific areas. Our findings provide important insight into the conservation of bottlenose wedgefish in northwestern Australia, including potential effectiveness of protected areas and interactions with specific anthropogenic threats such as shoreline development and recreational beach fishing.

This study reports the metazoan ectoparasite fauna of juvenile Critically Endangered green sawfish, Pristis zijsron, and sympatric elasmobranchs in Western Australia. Five parasite taxa were found on 76 screened P. zijsron: Caligus furcisetifer (Copepoda: Caligidae), Dermopristis pterophila (Monogenea: Microbothriidae), Branchellion plicobranchus and Stibarobdella macrothela (Hirudinea: Piscicolidae), and praniza larvae of an unidentified gnathiid isopod. Only C. furcisetifer and D. pterophila were common, exhibiting discrepant site-specificity, with C. furcisetifer occurring mostly on the head and rostrum, and D. pterophila around the pectoral and pelvic fins. Intensity of infection for C. furcisetifer and D. pterophila increased with host total length and was influenced by host sex, but in opposite directions; intensity of C. furcisetifer was greater on female P. zijsron, whereas intensity of D. pterophila was greater on males. In the Ashburton River, likelihood of infection for C. furcisetifer and D. pterophila on P. zijsron increased with time since substantial freshwater discharge events, suggesting decreased salinity impacts both taxa. In addition to P. zijsron, five other sympatric elasmobranch species were opportunistically screened for ectoparasites in the study area: the giant shovelnose ray, Glaucostegus typus, the eyebrow wedgefish, Rhynchobatus palpebratus, the nervous shark, Carcharhinus cautus, the lemon shark, Negaprion acutidens, and the graceful shark, Carcharhinus amblyrhynchoides. Caligus furcisetifer was found on R. palpebratus; no other parasites of P. zijsron were found on other sympatric elasmobranch species. Conversely, Perissopus dentatus (Copepoda: Pandaridae) was found on all three carcharhinids but not on batoid rays (P. zijsron, G. typus or R. palpebratus).
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•The ectoparasite fauna of green sawfish, Pristis zijsron, is reported.•Caligus furcisetifer and Dermopristis pterophila were common on P. zijsron.•Stibarobdella macrothela, Branchellion plicobranchus and gnathiids were scarce.•Host size and sex affects infection intensity of C. furcisetifer and D. pterophila.•Eyebrow wedgefish, Rhynchobatus palpebratus, were also infected by C. furcisetifer.