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Despite accelerated global population declines due to targeted and illegal fishing pressure for many top-level shark species, the impacts of coastal habitat modification have been largely overlooked. We present the first direct comparison of the use of natural versus artificial habitats for the bull shark, Carcharhinus leucas, an IUCN 'Near-threatened' species--one of the few truly euryhaline sharks that utilises natural rivers and estuaries as nursery grounds before migrating offshore as adults. Understanding the value of alternate artificial coastal habitats to the lifecycle of the bull shark is crucial for determining the impact of coastal development on this threatened but potentially dangerous species. We used longline surveys and long-term passive acoustic tracking of neonate and juvenile bull sharks to determine the ontogenetic value of natural and artificial habitats to bull sharks associated with the Nerang River and adjoining canals on the Gold Coast, Australia. Long-term movements of tagged sharks suggested a preference for the natural river over artificial habitat (canals). Neonates and juveniles spent the majority of their time in the upper tidal reaches of the Nerang River and undertook excursions into adjoining canals. Larger bull sharks ranged further and frequented the canals closer to the river mouth. Our work suggests with increased destruction of natural habitats, artificial coastal habitat may become increasingly important to large juvenile bull sharks with associated risk of attack on humans. In this system, neonate and juvenile bull sharks utilised the natural and artificial habitats, but the latter was not the preferred habitat of neonates. The upper reaches of tidal rivers, often under significant modification pressure, serve as nursery sites for neonates. Analogous studies are needed in similar systems elsewhere to assess the spatial and temporal generality of this research.

Satellite derived sea surface temperatures (SSTs) are often used as a proxy for in situ water temperatures, as they are readily available over large spatial and temporal scales. However, contamination of satellite images can prohibit their use in coastal areas. We compared in situ temperatures to SST foundation (~10 m depth) at 31 sites inshore of the East Australian Current (EAC), the dynamic western boundary current of the south Pacific gyre, using an area averaging approach to overcome coastal contamination. Varying across- and along-shelf distances were used to area average SST measurements and de-correlation time scales were used to gap fill data. As the EAC is typically anisotropic (dominant along-shore flow) the choice of across-shelf distances influenced the correlation with in situ temperatures more than along-shelf distances. However, the “optimal” distances for both measurements were within known de-correlation length scales. Incorporating both SST area and time averaging (based on de-correlation time scales) produced data for an average of 96% of days that in situ loggers were deployed, compared to 27% (52%) without (with) area averaging. Temperature differences between the in situ data and SSTs varied depending on time of year, with higher differences in the austral summer when daily in situ temperatures can range by up to 4.20°C. The differences between the in situ and SST measurements were, however, significant with or without area averaging (t-test: p-values < 0.05). Nevertheless, when using the area averaging approaches SSTs were only an average of ~1.05°C different from in situ temperatures and less than in situ temperature fluctuations. Linear mixed models revealed that latitude, distance to the coast and nearest estuary did not influence the difference between the in situ and satellite data as much as the water depth. This study shows that using de-correlation length and time scales to inform how to process satellite data can overcome contamination and missing data thereby greatly increasing the coverage and utility of SST data, particularly in coastal areas.

The carcass of a critically endangered, juvenile female grey nurse shark (Carcharias taurus, Rafinesque 1810) was recovered from a south‐eastern Australian beach and subjected to necropsy. The 1.98‐m‐long shark exhibited advanced cachexia with its total weight (19.0 kg) and liver weight (0.37 kg) reduced by 60% and 89%, respectively, compared with a healthy individual of the same length. Marked tissue decomposition was evident preventing histopathology and identification of a definitive cause of death. At necropsy, the abdominal organs were abnormally displaced and showed marked reductions in size compared with a healthy individual of the same size. Importantly, a hook‐shaped enterolith (HSE), with a rough surface and cream in colour, was found within the spiral valve of the intestine and is to the authors’ knowledge, the first description of such in any marine animal. X‐ray diffractometry showed that the HSE comprised the minerals monohydrocalcite (Ca[CO₃].H₂O; ~70 wt%) and struvite (Mg [NH4] [PO4]. [H2O]6; ~30 wt%). A CT scan showed concentric lamellate concretions around a 7/o offset J‐hook that formed the nidus of the HSE. Nylon fishing line attached to the hook exited the HSE and was evident in the abdominal cavity through a perforation in the intestinal wall where the posterior intestinal artery merges. The most parsimonious reconstruction of events leading to enterolithiasis and secondary cachexia in this shark was the consumption of a hooked fish and subsequent hook migration causing perforations of the cardiac stomach wall followed by the thin, muscular wall of the apposed, sub‐adjacent intestine. Hook‐shaped enterolith found in the intestine of a stranded, immature female grey nurse shark, Carcharias taurus, that exhibited advanced cachexia. The enterolith was composed of the minerals monohydrocalcite and struvite and a 7/o offset J‐hook formed the nidus. Nylon line attached to the hook (enterolith) was also evident in the abdominal cavity via a perforation of the intestine.

The capture of four female Ragged-tooth Sharks, Carcharias taurus, in the early stages of pregnancy in the bather protective nets along the KwaZulu-Natal coastline provided an opportunity to investigate embryonic development. A total of 31 embryos, 8–225 mm total length, were found. Of these, 15 were encapsulated and 16 were found free-floating in the uterus. Six embryos, three of which were encapsulated (35–50 mm) and three free-floating (36–52 mm), were examined under both light and scanning electron microscopy. The embryos possessed tooth-like structures. Spectral analysis of these structures revealed the presence of calcium, phosphorus, fluoride and oxygen, which supports the hypothesis that they are teeth. These teeth would enable embryos to escape encapsulation. These free-floating embryos are the smallest on record, with the previous smallest being a 40 mm embryo. These findings would now amend the current literature of C. taurus embryology. These results could affect the current understanding of C. taurus reproduction and biology and may impact any current breeding programs that are attempting to increase the fecundity of these species.

The patrolling behavior of the critically endangered grey nurse shark (Carcharias taurus) comprising the occupation of, and movements between, two locations at Fish Rock (off eastern Australia) was documented using passive acoustic telemetry. Sharks occupied the locations symmetrically, asymmetrically, randomly, and nonrandomly. Passive acoustic telemetry was also used to provide a preliminary assessment of the impacts of scuba diving tourism on patrolling behavior. Maintaining natural behaviors unaffected by anthropogenic disturbances including scuba diving tourism is essential for the recovery and long-term conservation of this critically endangered species. The patrolling behavior of replicate sharks on any given day was similar but varied subtly and sometimes markedly in the periods before, during, and after scuba diving typically occurs. In contrast, patrolling behavior varied substantially among days with and without scuba diving; however, this was not statistically significant. Scuba diving did not impact the occupation of, or movements between, the locations by grey nurse sharks. Instead it is likely that the sharks responded to oceanographic features, localized currents, and prevailing sea conditions by adopting a range of swimming behaviors to conserve energy, and this accounted for the variation in patrolling behavior among days. Future research at other aggregation sites, during different lunar phases and with sharks at various life history stages should be done to confirm the findings of this first assessment and to enhance the generality of the results to grey nurse sharks elsewhere. Regular monitoring of grey nurse shark scuba diving tourism should be done to ensure that any anthropogenic disturbances are identified so that mitigation can be implemented.