Hello ECS and MARMAM readers Apologies for cross posting. On Saturday 5th April 2014 at the upcoming European Cetacean Society conference in Liege a discussion workshop on "Estimating the probability of detection from passive acoustic data" will be held in the Aquarium. The workshop will cost 10 Euros and will run from in the afternoon from 1400-1800. Background: Assessing the status of cetacean populations, and the impacts of and level of risk associated with anthropogenic activities is hampered by limited abundance estimates for many areas. While abundance estimation by visual means is possible for cetaceans, surveys are often limited by weather conditions, eye height of observers, availability bias, high cost and observer inconsistency. For those species that vocalise routinely, passive acoustic techniques have been proposed as a more accurate and efficient method of detection and can be utilised in poor weather conditions and at night time. Absolute abundance and population estimates from acoustic data have been derived for animals which vocalise loudly and predictably, such as sperm whales. However for animals which do not vocalise constantly or produce vocalisations that may be relatively quiet or highly directional, the probability of detection, needs to be determined empirically in order to calculate absolute abundance or density estimates from acoustic edata. Abundance estimation using acoustic techniques rely on deriving a probability of detection which not only accounts for the amount of time an animal vocalises, but also accounts for those times when vocalisations might not be detected when animals orientate away from the hydrophone, temporarily reduce the source level of vocalisations or when the depth of a vocalising animal may influence likelihood of detection. Several research groups have collected acoustic data sets utilising static recorders or line transect methodologies and due to weather constraints, logistical limitations, poor planning or suboptimal sighting conditions, were not able to collect visual and / or acoustic data which would allow the probability of detection and the level of responsive movement to be characterised. These data could substantially increase our knowledge on the seasonal and regional abundance of species and inform critical conservation and management actions. Objectives: For this workshop we aim to bring together interested scientists in order to discuss and brainstorm methodologies suitable for providing probabilities of detection in order to 'unlock' the previously collected datasets, albeit with some caveats. Additionally we would like to stimulate discussion on the development of best practise for estimating probability of detection when acoustic data are being collected, especially for those areas and species where visual techniques are significantly constrained. The workshop will discuss methods to estimate the probability of detection for towed and static passive acoustic studies with particular focus on discussing the challenges animal group size, vocalisation depth, background noise and behavioural adaptations to vocalisation rate and detectability add to estimating the probability of detection. If you would like to attend or offer to do a presentation at the workshop please contact: <mailto:acuknell@mcr-team.org> acuknell@mcr-team.org.