Todd Bond

Evidence of large, local variations in recruitment and mortality in the small giant clam, Tridacna maxima, at Ningaloo Marine Park, Western Australia

Understanding variability of recruitment and mortality is essential for attempts to conserve populations or assessing changes resulting from perceived disturbances. In the absence of long-term studies, we examined population density and size-frequency distributions of the small giant clam, Tridacna maxima, at 20 sites in Ningaloo Marine Park, Western Australia, where the clams are abundant on discontinuous, intertidal rocky platforms attached to the shoreline. Density ranged over two orders of magnitude (0.04–8.27 m–2), and size ranged from 1.5 to 31.0 cm. The shapes of the size-frequency distributions varied substantially, indicating variability in recruitment and mortality, including failures of cohorts to recruit and catastrophic events of mortality. Consistency of recruitment, as indexed by the coefficient of variation of the size-frequency distribution, was greater towards the north of the Park, on intertidal platforms with greater complexity across their widths, and with smoother surfaces in the part of the platform occupied by the clams. The average turnover time was estimated at 5.4 years, giving a median age of 13 years. However, variation among sites was large, highlighting the importance of variability of the dynamics of local populations and the need for long-term studies to understand any particular population.

A novel stereo-video method to investigate fish–habitat relationships

Habitat complexity is known to influence the structure of fish assemblages. A number of techniques have previously been used to measure complexity, including quantitative in-situ methods, that can be time consuming and labour intensive, and more rapid semi-quantitative visual scoring methods. This study investigated the utility of a novel method for estimating complexity, whereby habitat height was measured using stereo photogrammetry from diver operated stereo-video, traditionally used to sample fish assemblages. This ‘stereo-height’ method was compared to established in-situ and visual scoring techniques and found to produce similar estimates of complexity. To determine how relevant the proposed method is for assessing ecological relationships, it was then used in conjunction with visual scoring of relief and point-intercept samples of benthic composition to model fish-habitat associations in the Pilbara region of Western Australia. Visual scores of relief were marginally stronger predictors of fish assemblage parameters and functional groups than the stereo-height measurements, providing support for the visual scoring approach. The only exception was for corallivorous fishes, which were more strongly correlated with stereo-height measurements. This study has presented a method for assessing habitat complexity using video imagery that is both comparable to traditional in-situ techniques and useful for investigating fish-habitat relationships. We suggest that future studies interested in collecting habitat complexity data from new or existing stereo-video samples use both the stereo-height and visual scoring methods presented here. Together these methods enable studies to rapidly and effectively assess fish-habitat relationships across a range of habitats without the need for in-situ methods or solely relying on field observers trained in visual scoring techniques. This article is protected by copyright. All rights reserved.

Network of small no-take marine reserves reveal greater abundance and body size of fisheries target species

No-take marine reserves (NTRs), i.e. areas with total fishing restrictions, have been established worldwide aiming to provide biodiversity and ecosystem conservation. Brazil has established NTRs, but currently lacks scientific knowledge and understanding of their ecological role, particularly regarding rocky reefs in subtropical regions. Consequently, this study aimed to contrast NTR, from the 30 year old Tupinambás Ecological Station, and comparable fished sites across a coastal biogeographic gradient to investigate the effect of fishing and habitat variability on the abundance and body-size of rocky reef fish. We used Baited Remote Underwater stereo-Video (stereo-BRUVs) and Diver Operated stereo-Video (stereo-DOVs) systems to simultaneously sample reef fish and habitat. Model selection and results identified habitat and biogeographic variables, such as distance from shore, as important predictor variables, explaining several aspects of the fish assemblage. The effect of protection was important in determining the abundance and body-size of targeted species, in particular for epinephelids and carangids. Conversely, species richness was correlated with habitat complexity and not with protection status. This is the first study to publish data using these novel survey methods in the Southeastern Atlantic and demonstrate their utility, in combination with an established network of NTR’s, to provide benchmarks for conservation and fisheries management.

Understanding the Global Scientific Value of Industry ROV Data, to Quantify Marine Ecology and Guide Offshore Decommissioning Strategies

This paper describes the potential global scientific value of video and other data collected by Remotely Operated Vehicles (ROVs). ROVs are used worldwide, primarily by the offshore oil and gas industry, to monitor the integrity of subsea infrastructure and, in doing so, collect terabytes of video and in situ physical data from inaccessible regions and poorly understood marine environments. The paper begins by describing how recent ROV surveys for projects in Australia have gained a new dimension by involving marine scientists in their interpretation. A previously unrecognised influence of marine life on oil and gas pipelines was uncovered, triggering new collaborations between industry and marine science. This new collaboration prompted a team of international engineers and marine scientists to gather together with West Australian based members of the oil and gas sector and ROV operators, to examine the global scientific value of ROV-collected data. If made available for research, these data have immense value for science to quantify the marine ecology and assist good stewardship of this environment by industry. It was found that most ROV operations are conducted by industry in a way that fulfils immediate industry requirements but which can confound scientific interpretation of the data. For example, there is variation in video resolution, ROV speed, distance above substrate and time (e.g. both seasonal and time of day), and these variations can limit the quantitative conclusions that can be drawn about marine ecology. We examined potential cost-effective, simple enhancements to standard ROV hardware and operational procedures that will increase the value of future industrial ROV operational data, without disrupting the primary focus of these operations. The ecological value of existing ROV data represents an immense and under-utilized resource with worldwide coverage. We describe how ROVs can unravel the mysteries of our oceans, yield scientific discoveries, and provide examples of how these data can allow quantification of the ecological value of