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Marine reserves are used as a management tool to conserve biodiversity and maintain ecological processes essential to ecosystem function. Grazing by herbivorous fish contributes to maintaining resilient reefs and marine reserves are important in conserving herbivores and their functional role. On the east coast of Australia, herbivores from the closely related families Girellidae and Kyphosidae are targeted by fishers and marine reserves have been shown to support greater size and abundance of girellids and kyphosids which enhances grazing on temperate reefs. On the west coast, however, kyphosids and girellids are rarely targeted by fishers. This study tested the hypothesis that there would be no difference in the size, abundance and feeding rates of girellids and kyphosids on temperate reefs inside and outside marine reserves at Rottnest Island, Western Australia, due to their relatively low levels of exploitation. The size, abundance and feeding rates of girellids and kyphosids inside and outside marine reserves were quantified using a diver-operated stereo-video system and feeding trials. No significant difference was found in the size and abundance of Kyphosus cornelii and Kyphosus spp. ( Kyphosus sydneyanus and Kyphosus gladius combined) or feeding rates inside and outside marine reserves. The second aim of the study was to assess the relative importance of grazing and drift-feeding pathways used by kyphosids. Drift-feeding is an alternative form of herbivory to grazing and herbivores switching between grazing and drift-feeding pathways can have significant effects on algal communities, yet little is known about the relative importance of both feeding strategies for fish. A combination of feeding observations (mensurative) and feeding trials (manipulative) were used to quantify the number of feeding bites taken by fish on drift algae and attached algae. There was no significant difference in the number of feeding bites taken by the abundant herbivore, K. cornelii , on drift algae and attached algae during feeding observations, however, during feeding trials herbivores consumed significantly more drift algae ( Ulva sp.) than attached algae. These findings demonstrate that drift-feeding is a common feeding strategy used by kyphosids. The findings in this study also highlight considerable differences in the effects of marine reserves on targeted east coast and non-targeted west coast populations of girellids and kyphosids on temperate reefs.

A key objective of marine reserves is to maintain ecological processes important to the functioning of marine ecosystems. Grazing by tropical herbivores contributes to maintaining resilient coral reefs and marine reserves are critical in conserving herbivores and the functional role they provide. Less is known, however, about the effects of marine reserves on herbivorous fish and their role on temperate reefs. This study evaluated the potential for marine reserves to enhance grazing by herbivores on temperate reefs in Jervis Bay Marine Park, Australia. First, the movement patterns of a dominant grazer, luderick Girella tricuspidata , were determined using acoustic telemetry to assess the potential effects of marine reserves on G. tricuspidata . Second, the size and abundance of G. tricuspidata and other grazers (rock blackfish Girella elevata and silver drummer Kyphosus sydneyanus ) was quantified on shallow subtidal reefs inside and outside marine reserves using a diver operated stereo-video system. Finally, grazing rates were quantified inside and outside marine reserves using video cameras. Luderick G. tricuspidata exhibited strong site fidelity on shallow subtidal reefs and was significantly larger and more abundant within marine reserves. Rock blackfish G. elevata was significantly more abundant in one of four marine reserves, although showed no difference in size between zones. Silver drummer K. sydneyanus was significantly larger in marine reserves, although not significantly more abundant. On shallow subtidal reefs, G. tricuspidata was the dominant grazer compared to other girellids and kyphosids, accounting for > 97% of total algal bites (predominantly on algal turfs). Grazing rates were higher on average within marine reserves (although not significantly higher) and there was a positive correlation between the relative abundance of G. tricuspidata and number of algal bites, indicating grazing intensity increased with abundance. The findings in this study demonstrate the clear potential for greater grazing by herbivores within temperate marine reserves. This study also suggests that exploitation of targeted herbivores on temperate reefs is significant and marine reserves can reduce this impact and allow it to be measured via reference areas.

Baited Remote Underwater Video (BRUV) has become a popular technique to survey fish assemblages for a wide range of purposes. BRUV methodology has, however, also varied greatly for a range of reasons. A major dichotomy occurs, in particular, in the time used to sample the fish assemblages i.e. the BRUV set time. The aim of this study was to determine whether differences in set time were likely to affect the conclusions reached by studies using different set times, and what might be the most appropriate and cost-effective set time to use to sample temperate reef fish assemblages. In this study, we test whether there were significant differences between the two main set times used (i.e. 30 and 60 min) in BRUV sampling for assemblage patterns, species diversity, and relative abundance of rocky reef fishes. In particular, we sampled fished and unfished rocky reefs to assess whether the different set times would lead to differences in the patterns or the interpretation of the subsequent data. We sampled fish assemblages on six rocky reefs (20–35 m) across two marine parks on the east coast of Australia. At each location replicate BRUVs were deployed for 30 and 60 min in a ‘no take’ area (marine sanctuary) and a fished area. The interpretations of the data across the fished and unfished zones were consistent with both set times indicating that the conclusions from both set time were comparable. Furthermore, there were no differences in fish assemblages or species richness between the set times. The relative abundances of the recreationally and commercially important snapper ( Chrysophrys auratus ) were greater in the longer set times, but the actual spatial patterns between zones and amongst locations were consistent. Piecewise regression analysis of the breakpoint times for species accumulation found that there were no significant differences between locations or between fished and unfished areas. Mean breakpoint, the time when species accumulation changes, occurred at 12 min ± 1.04 S.E. for all sites combined whilst the shorter set time was found to be less costly and require less field and laboratory times. This study quantifies that either 30 or 60 min will provide a reasonable estimate of rocky reef fish diversity and relative abundance for comparative purposes, on these shallow rocky reefs.

Heavy metals often occur at elevated concentrations in bays and estuaries surrounded by urbanised areas and can cause substantial ecological changes to marine communities. The toxic effect of heavy metals can be modified by a several physico-chemical processes in the marine environment. These processes can vary greatly over small scales, so it is likely that the ecological effects of heavy metals on marine biota also vary substantially over similar spatial scales. We used a manipulative field experiment to assess the spatial variation in the effect of copper on sessile invertebrates within a marina and tested whether this variation was influenced by variation in localised water flow. Effects of copper were not consistent over relatively small spatial scales (i.e. metres) for all sessile invertebrate species. Three of the twenty sessile invertebrates from our experimental assemblages showed significant small scale variation in the effect of copper at the scale of metres. For these taxa, the effect of copper varied in magnitude and direction. We had predicted that the effect of copper would diminish with increased water flow, but this did not occur for any taxa. We suggest that variations in the presence of organic or inorganic compounds or in pH within the marina may provide alternative explanations for the spatially variable effects detected in this study. Our study's findings highlight the need for future field assessments of the complex physical, chemical and biological influences on the ecological effects of heavy metals, particularly at small spatial scales. Such studies are the key to improving our prediction about the effects of heavy metals on marine organisms and aid in better characterisation of the risk of heavy metals in the marine environment.