Globally, seagrasses and other estuarine habitats are under threat from a range of human disturbances, including boating‐related activities. The fixed, block‐and‐chain swing moorings used to secure boats in many countries can create visible scars in seagrass meadows and remove other benthic organisms. Losses of seagrasses in two estuaries in New South Wales (NSW), Australia, were quantified using aerial imagery and used to estimate estuarine habitat damage across the remainder of the state. The rate of mooring scar development was approximated and factors influencing the size of mooring scars were identified. Individually mapped mooring scars in meadows of the endangered Posidonia australis ranged from 55 to 706 m2, and were generally larger than those in the more opportunistic seagrass Zostera muelleri subsp. capricorni (22–342 m2). Scar size in both species of seagrass increased significantly with depth and boat length. The rate of increase in the size of mooring scars amongst P. australis was roughly linear over 4.8 years, averaging 6.3 m2/month up to a maximum of 16.7 m2/month for one 16‐m yacht. Across all of NSW, it was estimated that currently leased moorings were causing losses of 129 884 m2 of P. australis and 93 940 m2 of Z. capricorni, and disturbing 2 790 907 m2 of non‐vegetated soft sediments. NSW seagrass loss estimates relate only to damage from current moorings and could be underestimated by ~41% for P. australis if estuaries contain many old scars that remain after the relocation of moorings (as has occurred in Lake Macquarie). Mandating the use of moorings that do not rely on a chain dragging on the sea bed would greatly reduce future physical damage of benthic habitats and enable some recovery from legacy effects.

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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.

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1. Although it is well established that human activities are linked to the loss of seagrasses worldwide, the influence of anthropogenic disturbances on the habitat fragmentation of seagrass meadows is less understood. This information is essential to identify how humans are modifying seascapes and what disturbances pose the greatest risk to seagrasses, which is pertinent given the rapid urbanization occurring in coastal areas. This study examined how the habitat fragmentation of an endangered seagrassPosidonia australis varied in relation to several anthropogenic disturbances (i.e. human population, marine infrastructure, terrestrial run-off and catchment land-usage) within 10 estuaries across 620 km of coastline in New South Wales, Australia.3. When comparing between estuaries, the fragmentation of P. australis meadows was significantly greater in estuaries adjacent to highly populated metropolitan centresgenerally in the Greater Sydney region. At sites within estuaries, the density of boat moorings was the most important predictor of habitat fragmentation, but there was also evidence of higher fragmentation with increased numbers of jetties and oyster aquaculture leases.4. These results suggest that the fragmentation of seagrass meadows will become more pervasive as the human population continues to grow and estuarine development increases. Strategies to mitigate anthropogenic disturbances on seagrass meadow fragmentation could include prohibiting the construction of boat moorings and other artificial structures in areas where seagrasses are present or promoting environmentally friendly designs for marine infrastructure. This knowledge will support ongoing management actions attempting to balance coastal development and the conservation of seagrasses.

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