Marine Protected Areas (MPAs) can either protect all seabed habitats within them or discrete features. If discrete features within the MPA are to be protected humans have to know where the boundaries are. In Lyme Bay, SW England a MPA excluded towed demersal fishing gear from 206 km(2) to protect rocky reef habitats and the associated species. The site comprised a mosaic of sedimentary and reef habitats and so 'non reef' habitat also benefited from the MPA. Following 3 years protection, video data showed that sessile Reef Associated Species (RAS) had colonised sedimentary habitat indicating that 'reef' was present. This suggested that the functional extent of the reef was potentially greater than its visual boundary. Feature based MPA management may not adequately protect targeted features, whereas site based management allows for shifting baselines and will be more effective at delivering ecosystem goods and services.

1. Managing ecological systems, which operate over large spatial scales, is inherently difficult and often requires sourcing data from different countries and organizations. The assumption might be made that data collected using similar methodologies are comparable, but this is rarely tested. Here, benthic video data recorded using different towed underwater video systems (TUVSs) were experimentally compared. 2. Three technically different TUVSs were compared on different seabed types (rocky, mixed ground and sandy) in Kingmere Marine Conservation Zone, off the south coast of England. For each TUVS, species metrics (forward facing camera), seabed impact (backward facing camera) and operational performance (strengths and limitations of equipment and video footage) were compared with the aim of providing recommendations on their future use and comparability of data between different systems. 3. Statistically significant differences between species richness, density, cover and assemblage composition were detected amongst devices and were believed to be mostly due to their optical specifications. As a result of their high image definition and large field of vision both the benthic contacting heavy and benthic tending TUVS provided good quality footage and ecological measurements. However, the heaviest TUVS proved difficult to operate on irregular ground and was found to cause the most impact to the seabed. The lightest TUVS (benthic contacting light) struggled to maintain contact with the seabed. The benthic tending TUVS was able to fly over variable seabed relief and was comparably the least destructive. 4. Results from this study highlight that particular care should be given to sled and optic specifications when developing a medium-or long-term marine protected area monitoring programme. Furthermore, when using data gathered from multiple sources to test ecological questions, different equipment specifications may confound observed ecological differences. 5. A benthic tending TUVS is recommended for benthic surveys over variable habitat types, particularly in sensitive areas, such as marine protected areas.

The effects of different holding methods on heart rate (HR) changes in the green crab, Carcinus maenas (Linnaeus, 1758), were investigated. Green crabs were held in perforated plastic boxes (with or without a layer of sand) suspended above the bottom of the tank or strapped to a weighted plastic grate. The HR of green crabs classified as unrestrained (plastic box with or without sand) dropped more rapidly compared with restrained (hanging from band, strapped to grate) green crabs. Within 1 h, unrestrained green crabs exhibited periods of cardiac pausing accounting for between 8% and 14% of the hourly time. In contrast, restrained green crabs rarely exhibited cardiac pausing. When the green crabs were subjected to a temperature increase (10–30 °C), the HR of unrestrained green crabs reached higher levels than that of the restrained animals. The four restraining methods were also used to investigate cardiac responses to hypoxia. During progressive hypoxia (100%–20% oxygen), the HR of unrestrained green crabs declined to lower levels than that of the restrained animals. The restraining methods appeared to be more stressful for the green crabs that maintained elevated HRs and were less able to respond to environmental change compared with green crabs that could move freely within a small chamber. This suggests that even subtle changes in experimental design may alter physiological responses.

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