1. Coral-reef managers must detect and reverse collapses in habitat and evaluate the success of such interventions. Since these responsibilities must be met with limited time and resources, methods used should balance statistical power with practical and logistical constraints.2. Photoquadrat analysis is a commonly used method to survey coral habitats. This method, which involves photographing substratum along transects and digitally analysing habitat at points on the 'photoquadrats', affords efficiency in the field but is costly and requires extensive desk-based analysis. It remains unclear what is the optimal combination of sampling units (points, photoquadrats and transects) needed to detect important trends in coral habitat.3. Here, a dataset on Philippine coral-reef habitats, collected using intensive photoquadrat surveys, was used to explore the reliability of using different numbers of points per photoquadrat, photoquadrats per transect and transects per site to detect spatial differences in habitat.4. Results of leave-some-out analyses were compared with analysis of the complete dataset. Using fewer points per photoquadrat and fewer photoquadrats per transect caused little decline in ability to detect key trends, and lessened desk-based time; reducing the number of photoquadrats also lessened field time. Using fewer transects reduced time requirements but at the expense of statistical reliability. 5. Prospective power analyses revealed that common rates of coral recovery could not be detected using even the most intensive photoquadrat protocols. This result implies that coral recoveries within protected areas might go undetected using standard surveying techniques. 6. Using fixed rather than randomly placed photoquadrats, or more sensitive indicators of habitat recovery than coral cover (e.g. coral surface area) may improve power to detect coral recoveries. Finally, protocols that minimize desk time rarely also minimize field time and vice versa, which highlights the need to prioritize different logistical constraints when designing methods.

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SUMMARYIn marine environments, charismatic or economically valued taxa have been used as flagships to garner local support or international funds for the establishment and management of marine protected areas (MPAs). Seahorses (Hippocampus spp.) are frequently used as flagship species to help engender support for the creation of small community-managed no-take MPAs in the central Philippines. It is thus vital to determine whether such MPAs actually have an effect on seahorse abundance, reproductive status and size. A survey of seahorses inside and immediately adjacent to eight MPAs, and in four distant unprotected fishing areas, showed these MPAs had no significant effect on seahorse densities; although densities in and near MPAs were higher than in the distant fished sites, seahorse densities did not change over time. Seahorse size did show a marginal reserve effect, with slightly larger seahorses being found inside MPAs as compared to the distant unprotected fishing areas, but, in general, MPAs had little impact on seahorse size. Although MPAs may eliminate local fishing pressure, they may not reduce other threats such as pollution or destructive fishing outside the reserves. Other recovery tools, such as ecosystem-based management, habitat restoration and limits on destructive fishing outside of MPAs, may be necessary to rebuild seahorse populations. The effects of MPAs depend on species, as well as conditions outside the reserve boundaries. MPA management objectives must thus be clearly and realistically articulated to the communities, especially if support for an MPA was derived at least partly to conserve a particular flagship species.

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For many small-scale, tropical reef fisheries, landed catch may be the only data that can be monitored to assess the impacts of management. This is true for seahorses Hippocampus comes that are obtained as part of a multi-species fishery in the Philippines. Here, because seahorses are locally rare and depleted, it is difficult to attain large enough sample sizes to detect changes over time using underwater surveys. We assessed changes in seahorse sales at 2 sites, from 1996 and 2005 respectively to 2010. The study period covered local and national conservation initiatives that could affect seahorses and dependent fisheries: establishment of marine reserves (1998 onwards), a community-led minimum size limit (MSL: 2002(MSL: to 2004) and a national ban on seahorse fishing (from 2004). The MSL appeared to lead to increased sizes of seahorses in trade, as hoped, while the national ban led, perversely, to more fishers selling seahorses. Declines in overall take after 2004 or 2007 (depending on the site) is likely linked to declining seahorse populations rather than reduced effort, especially when one considers the increased number of fishers and the price per seahorse. It is notable that communities decided on the MSL, whereas the government imposed the ban on capturing seahorses. In this small-scale, multi-species fishery, monitoring a wide range of variables intensively over a relatively long time scale allowed us to identify key differences between small-scale and industrial fisheries management, and also to document the biological and social consequences of management action for a depleted, threatened species.