APEM Group Enhances Digital Aerial Survey Data Precision with IMU Technology
Over the past year, APEM Ltd, part of APEM Group, has refined its digital aerial survey (DAS) methodology to deliver...
Following our recent webinar, Understanding Marine Mammal Survey Data for Project Approval, we received some thoughtful questions from attendees. While we couldn’t address them all live, we’ve compiled responses here to continue the conversation. Thank you to everyone who contributed questions and engaged with the panel.
-
Why is seal biologging included in EIAs, given their mobility, limited tagging data, and ethical concerns?
Seal biologging is included in Environmental Impact Assessments (EIAs) because it provides uniquely detailed insights into the fine-scale movement, foraging behaviour, and habitat use of seals; data that are otherwise difficult to obtain through traditional survey methods. This is particularly valuable in offshore wind development, where understanding how marine mammals interact with proposed infrastructure is critical. For example, Australian fur seals, central-place foragers during lactation, may forage within or near wind farm footprints, making biologging an effective tool for identifying potential spatial overlaps.
In addition, Australian fur seals are primarily benthic foragers, raising concerns about the potential impacts of any construction on the seafloor. While evidence from the Northern Hemisphere may suggest that offshore wind development has negligible effects on seals, it is not currently possible to draw the same conclusions for Southern Hemisphere species. Therefore, biologging remains a necessary component in the collection of baseline data.
Despite ethical and permitting challenges, such as the need for sedation and close handling, these activities are carefully managed through rigorous ethical review processes, permits from wildlife authorities, and adherence to best-practice animal welfare standards. Staff undertaking these surveys are also highly trained and experienced. Limitations in the number of individuals that can be tracked could be overcome through the inclusion of biologging work in a regional-scale program.
Biologging is most justified when other methods cannot provide the necessary behavioural or spatial data, especially for assessing availability bias in aerial or boat-based surveys.
-
How should we manage climate uncertainty in rapidly changing areas like the Bass Strait when designing surveys and collecting data?
Managing climate uncertainty in dynamic regions like the Bass Strait requires a flexible and adaptive approach to survey design. Surveys are structured to accommodate seasonal and interannual variability, ideally spanning at least two years to capture a representative range of environmental conditions. Certain species are known to be more sensitive to a changing climate, and ensuring high levels of temporal and spatial coverage, as well as utilising multiple methods of data collection, allows us to better understand these sensitivities and changes.
Modelling tools such as species distribution models (SDMs) and scenario planning frameworks can help anticipate how species distributions may shift under different climate futures. Long-term datasets, including oceanographic and biological records, are also critical for contextualising current observations and identifying trends. By integrating these tools and approaches, survey designs can remain robust and relevant, even in the face of rapid environmental change.
-
What are the risks of relying solely on boat-based surveys, especially when species ID is more robust compared to DAS?
While boat-based surveys offer high species identification rates and behavioural observations, relying on them exclusively poses several risks. These surveys are limited in spatial coverage due to slower vessel speeds and do not provide an archivable, auditable record of data that can be revisited to confirm species identifications and counts. Additionally, the presence of vessels can influence animal behaviour, either deterring or attracting certain species, potentially biasing results which require natural abundance and distribution data.
Observer fatigue and variability in detection skills can also affect data quality. In contrast, Digital Aerial Survey (DAS) can cover much larger areas quickly, is less intrusive, and provides permanent imagery for quality assurance. However, DAS may be less effective at identifying cryptic or small species.
A multi-method approach that combines boat-based surveys with DAS and passive acoustic monitoring (PAM) is therefore recommended. This integrated strategy leverages the strengths of each method, ensuring more comprehensive and reliable data for EIAs and reducing the risk of underestimating species presence or impact.
-
What is the swath width of your aerial survey system at typical flight altitudes?
APEM’s three-camera digital aerial survey system, using a standard survey set-up, achieves a swath width of approximately 650 meters. This configuration provides a ground sampling distance (GSD) of 1.5 centimetres, allowing for high-resolution imagery that can detect marine mammals both at the surface and just below it (depending on turbidity), and increased species identification due to the finer detail that is captured.
The exact swath width is dependent on several factors within the survey design, such as flight altitude. APEM’s camera configuration and large swath width make DAS a highly effective and cost-efficient method for broad-scale marine wildlife surveys. This setup is particularly well-suited for baseline and monitoring surveys in offshore wind development areas, where wide-area coverage and image clarity are essential.
Read our recent article to see how we have enhanced our DAS with new technology.
APEM’s ultra-high resolution digital aerial surveys are delivered throughout the world.
-
How do you correct for submerged animals in boat-based surveys? Are correction factors species-specific, and how is uncertainty handled?
In boat-based surveys, availability correction factors (ACFs) are used to account for the proportion of time marine mammals spend submerged and thus undetectable. These correction factors are species-specific, reflecting differences in dive behaviour and surfacing patterns.
ACFs are typically derived from biologging data, which provide detailed information on dive durations and surface intervals. To incorporate uncertainty, confidence intervals around ACFs are included in abundance estimates, and sensitivity analyses are often conducted to assess how variations in these factors affect results.
In some cases, Bayesian statistical methods are employed to integrate prior knowledge and quantify uncertainty more rigorously. This approach ensures that abundance estimates are as accurate and transparent as possible, even when direct observations are limited.
In addition to using ACFs or other statistical methods, implementing a multi-survey platform, including boat-based surveys, aerial surveys, and PAMs, will increase confidence in addressing uncertainties, as each method offers a unique set of benefits and limitations to the overall survey program.
-
If no marine mammals are detected during a 12-month boat-based survey, how does that affect EIA confidence, especially when locals report sightings?
The absence of detections in a 12-month boat-based survey does not necessarily indicate the absence of marine mammals, particularly for rare, cryptic, or seasonally present species.
Regulators and stakeholders recognise that non-detection can result from limited survey effort, poor weather conditions, or low detectability. Therefore, EIAs must interpret such findings cautiously and in context. To improve confidence, supplementary data sources should be considered, including community sightings, historical records, PAM data, and aerial surveys. These additional lines of evidence can help fill gaps and validate or challenge survey findings.
A weight-of-evidence approach is recommended, combining multiple data streams to build a more complete picture of species presence and potential impacts. Where uncertainty remains high, adaptive monitoring and post-approval data collection may be required to ensure that environmental commitments are met and that any unforeseen impacts are detected and addressed.
-
Does Seiche receive PAM data on seals, and if so, from which regions?
We have been recording bearded seals along with bowhead whales and other species regularly from real-time acoustic monitoring from our cable-to-shore PAM listening station off West Greenland.
We would expect grey seal and harbour seal vocalisations to be detectable on our stationary, ARC mooring recorders in European waters, but we are not aware of anyone analysing these data for seal detections. Â We’d expect vocalising pinnipeds to be detected in other regions, however, as the ARUs are sensitive across their vocalising frequencies.
Conclusion
As Australia’s offshore wind industry accelerates, the importance of robust, fit-for-purpose marine mammal data has never been greater. From biologging and aerial surveys to passive acoustic monitoring, each method offers unique insights and challenges. What’s clear is that no single approach can answer every question. Instead, a toolbox of complementary techniques, guided by clear regulatory expectations and scientific rigour, is essential for building confidence in environmental impact assessments.
We hope this Q&A has helped clarify some of the key considerations and trade-offs involved in marine mammal survey design. Thank you again to everyone who joined the webinar and submitted questions; your engagement is helping shape better outcomes for both industry and the environment.
For a quick recap, read our key takeaways article.
Contact us
Get in touch if you’ve got any questions for our panel
Related Articles
The Science Behind the Permit: Marine Mammal Data for Australian Offshore Wind
As Australia’s offshore wind sector gains momentum, developers are navigating a complex landscape of environmental regulations, stakeholder expectations, and ecological...
Mitigating Underwater Noise Impacts on Marine Mammals
Introduction to Australia’s Offshore Wind Development and its Environmental Challenges.