Population effects of Navy sonar on marine mammals?

We’re delighted to announce the release of two reports that we’ve produced working with the Office of Naval Research, exploring how the interim Populations Consequences of Disturbance (iPCoD) might be adapted to explore the population level effects of Navy exercises on marine mammal populations. In this study we focused on populations of Blainville’s beaked whales and sperm whales on US Navy ranges in the Bahamas and around Hawai’i.

The potential risk of injury and/or disturbance to marine mammals during US Navy activities is assessed as part of standard environmental impact assessment processes. Possible consequences of exposure to underwater noise from US Navy sonar include; disturbance that could cause marine mammals to either move away or change behaviour, suffer temporary hearing damage or permanent physical injury. The interim PCOD model assesses what the longer term and larger scale impacts of these consequences are to the exposed group(s) of animals as a whole.

The basic PCOD approach was developed by an international group of experts in the US Office of Naval Research (ONR) Working Group on the Population Consequences of Acoustic Disturbance (PCAD) US National Research Council’s Committee on Characterizing Biologically Significant Marine Mammal Behaviour in its 2005 report. Their work provided the foundation upon which the Interim PCOD framework is built.

The Interim PCOD model was specifically built to assess the impacts of offshore renewable energy development on UK marine mammals. It has been designed to use the kinds of information that are likely to be provided by developers in their Environmental Statements and Habitats Regulations Assessments. The model is freely available and allows the user to predict the population consequences of disturbance and injury on five key priority species of marine mammal found in the UK – bottlenose dolphins, harbour porpoise, minke whale, harbour and grey seals.

Such versions of the PCOD model are considered ‘interim’, because it was developed to help manage uncertainty within the current knowledge of marine mammals, where there are limited data available on some of the key information needed. For instance, relatively little is known about how changes in behaviour and hearing sensitivity caused by exposure to underwater noise affect the ability of individual marine mammals to survive and to reproduce (their ‘vital rates’). To combat this issue, SMRU Consulting received input from over 30 international marine mammal experts who delivered a range of opinions of how disturbance might impact on these vital rates of Blainville’s beaked whales and sperm whales.

You can read the main report here, which details the overall approach, how we dealt with eliciting information from experts and how the outputs of PCoD might be tailored to the US regulatory system. We also produced a report applying the PCoD Lite model for the two species of interest on ranges in the Bahamas and Hawai’i. These are very much theoretical and speculative and we specifically note:

It should be recognised that the results presented in this report are not intended in any way as an assessment of the potential effects of Navy training and testing activities on beaked whale or sperm whale populations. Nor is it intended to influence regulatory policy or control over these activities. Rather, we have attempted to show how the Interim PCoD approach can be used with information that is routinely collected on some Navy ranges, such as AUTEC, or that is provided by the Navy Acoustics Effects Model to forecast these potential effects.

We’ll have to announce on PCoD later in the next few weeks! Stay tuned!

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About the Author:

Cormac is a Principal Scientist and Director of Business Development at SMRU Consulting Europe. Check out his bio under the "About Us" tab.

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