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Comparative assessment of pelagic sampling methods used in marine monitoring

Phil Bouchet | Aug 17, 2018

Phil Bouchet

Aug 17, 2018

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Mid-water baited remote underwater video systems (BRUVS) are one of many ways to sample pelagic waters. Photo: Manu San Félix, National Geographic Society.

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Dr. Phil Bouchet
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Bouchet P, Phillips C, Huang Z, Meeuwig J, Foster S, Przeslawski R. 2018. Comparative assessment of pelagic sampling methods used in marine monitoring. Report to the National Environmental Science Programme, Marine Biodiversity Hub, 149 p.


  • Monitoring remote pelagic habitats and wildlife is critical to understanding how the world’s oceans are responding to human activities and global environmental change.
  • Doing so is challenging, however, not least because data can be collected in a variety of ways.
  • Additionally, available survey methods differ widely in costs, capabilities, mobilisation constraints, resolution, or sensitivity.
  • There is an urgent need to compare these methods to determine which are best suited to specific marine monitoring programmes.
  • We provide an in-depth synthesis of the advantages and caveats of multiple sampling tools commonly used in pelagic research.
  • A universal, one-size-fits-all approach to pelagic monitoring is not feasible and marine ecosystem monitoring will demand holistic approaches to sampling that capitalise on the combined strengths of multiple instruments deployed within coordinated networks.
  • While the simultaneous use of multiple methods has become increasingly common, their best combination remains unknown, in great part because optimal pairings depend on the target organisms, the habitats being explored, and the underlying survey objectives.


Australia’s Exclusive Economic Zone (EEZ) is the third largest maritime territory in the world. Monitoring its dynamics is fundamental to understanding and reporting on how the ocean is responding to human pressures and global environmental change. Increasingly stringent conservation budgets, however, are placing a strong emphasis on strategic resource allocation. Faced with mounting pressures to build accountability, managers and policy advisors must now more than ever make monitoring investment decisions that are both impactful and cost-effective. This can be challenging given the smorgasbord of modern survey tools currently available, most of which differ widely in costs, capabilities, mobilisation constraints, resolution, or sensitivity, and are evolving rapidly without always being critically evaluated or compared. Whilst pelagic waters present fascinating opportunities for ecological investigation, their extreme horizontal, vertical and temporal patchiness, as well as the huge size range of organisms inhabiting the open ocean, also pose important methodological challenges for sampling. Early pelagic studies relied heavily on capture sampling using nets. While these remain a critical component of biological and oceanographic research today, a rapidly increasing array of innovative technologies (e.g. drifting baited videography, environmental DNA, unmanned aerial vehicles) with various degrees of autonomy and sensory capabilities is revolutionising the way we quantify biophysical processes and observe wildlife in remote habitats. Protocols for choosing optimal combinations of methods for a given region, taxonomic/indicator group, or habitat remain generally unavailable. There is thus an urgent need to synthesise and compare these methods to determine how they can best support and strengthen the empirical evidence base available for implementing marine monitoring programmes. The aim of the present report is to provide a comparative assessment of commonly used pelagic sampling methods. We do this by undertaking a qualitative, yet comprehensive, review of the published literature to identify their potential advantages, limitations, and their relevance to monitoring efforts.



Time-space diagram showing the approximate temporal and spatial scales of pelagic sampling
methods used in marine monitoring.



Summary of interest in adopting a standardised pelagic monitoring protocol. (A) Density plots
showing the level of intent (on a scale of 1 to 100) to modify current methodology, between all respondents
(‘All’) and only those favourable to standardisation (‘Yes’). (B) Factors likely to increase interest in, and/or
uptake of, a standardised protocol. Segments denote response counts, and filled circles the corresponding
percentages (from a total of n=40 respondents). Data derived from an online questionnaire of marine professionals.


This work was undertaken for the Australian Government’s Marine Biodiversity Hub (MBH), a collaborative research partnership supported through funding from the Government’s National Environmental Science Programme (NESP). NESP MBH partners include the University of Tasmania, CSIRO, Geoscience Australia, Australian Institute of Marine Science, Museum Victoria, Charles Darwin University, the University of Western Australia, Integrated Marine Observing System, NSW Office of Environment and Heritage, NSW Department of Primary Industries. We sincerely thank the following individuals: G. Bearzi, L. Beckley, M. Byers, R. Downie, M. Guinea, N. Hardman-Mountford, T. Ingleton, T. Letessier, S. Marley, M. Mohring, M. Moussa, N. Patten, H. Pavanato, G. Pietroluongo, N. Pilcher, M. Rees, I. Silva, A. Sutton, R. Tait, B. Wilson, H. Wilson, and A. Wittich, as well as 40 other anonymous contributors for sharing their views and expertise in the online questionnaire (Section 3).