Part A: Biological Significance Workshop


  • Can the concept of Biological Significance be developed into an acceptable (to regulators) method of estimating the importance of various animal reactions to sound?
  • Can the PCAD model lead to a predictive model that is usable in risk assessment and regulations?
  • How can we incorporate the biological significance of behavioural response into industry risk management practices and future Programme research?


The U.S. National Research Council’s PCAD model (Population Consequences of Acoustic Disturbance)1 defines “biologically significant” effects of sound exposure as those that can cause changes in population levels. Since 2005, this model has held the promise of becoming a practical management tool if it could be given predictive capabilities. In 2007 the Programme started working toward that goal by holding a workshop of industry, government and academic participants to discuss ways to begin developing the model.

The workshop concluded that giving PCAD predictive capabilities was a daunting task. Nevertheless, PCAD was considered to be a useful framework for guiding research prioritisation and mitigation concepts. It recommended extending the model to cover cumulative effects of multiple sound sources over extended time periods and some non-acoustic challenges marine mammals face. It called for a better understanding of how changes in Life Function (surviving, feeding, mating, etc.) could affect population trends, and concluded that pinnipeds (seals) offered more research promise than did cetaceans. As an initial approach it suggested that population modelers develop concepts to bound the problem.

Objectives and methods

  • discuss industry and non-industry approaches to risk assessment
  • discuss how biological significance is considered in regulatory and permitting decisions
  • identify gaps and needed research to develop consistent use of biological significance concepts in project planning
  • develop a plan to include biological significance in industry risk management practices.


This workshop identified a specific type of model and several types of data that would be needed to begin moving toward a more workable, practical version of the PCAD model. It was the first attempt by any group to take this step.

Links to other research

Four subsequent projects, summarised in parts B and C below, were the direct result of this workshop.


Programme internal workshop

1Available at