1.Little is known about the ecological impacts of oyster culture structures on intertidal communities. In the present study, distribution and movement patterns of juvenile Chinese horseshoe crab, Tachypleus tridentatus were assessed on a mudflat at Ha Pak Nai in Deep Bay, Hong Kong.2. As the traditional bottom-laying method of using concrete posts as cultch for collecting oyster spat is a common practice in Hong Kong, structurally similar bricks were used to simulate the potential effects of cultch on intertidal flats.3. Over the two-month experimental period, all the tested sediment physico-chemical characteristics, including median particle size and total organic content, remained unchanged among the treatment areas. However, juvenile densities and foraging trails at low-and high-density brick areas were significantly lower/shorter compared with the adjacent bare areas. Such effects were more evident for larger individuals since significant correlations were found between foraging distance and juvenile prosomal width in no-brick areas, but not the low-and high-density brick areas. In addition, most juveniles (> 95%) were observed feeding along the outer boundaries of brick areas.4. Such findings imply that the extensive artificial structures in oyster cultivation sites could induce physical disturbance and alter the habitat use of juvenile horseshoe crabs in the intertidal zone. Considering the high conservation value of Chinese horseshoe crabs, appropriate mitigation measures should be implemented to buffer the detrimental effects on horseshoe crabs and other marine organisms of conservation concern that utilize intertidal habitats as nursery and hatchery grounds.

Turtles from Asia are on the brink of extinction with 53% of species considered endangered or critically endangered. Unfortunately, the ecology of many threatened species remains largely unknown. In this study, the diet of the endangered Beale’s eyed turtle (Sacalia bealei) was investigated using two methods, visual faecal content analysis and stable isotope analysis. Results from both methods indicated that S. bealei is highly reliant on riparian resources, especially fruits and terrestrial insects. Stable isotope data indicated that terrestrial resources made up around half (47–53%) of all assimilated food resources. These findings suggest that S. bealei facilitates energy flow from riparian forests to stream ecosystems. Moreover, S. bealei is likely to be a seed disperser for riparian plants. This study represents the first application of stable isotope methods to examine the diet of Asian freshwater turtles and their resource use. We stress the importance of similar studies to improve our understanding of remnant turtle populations before they disappear as a result of human activities.

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