Dear colleagues, We are pleased to share our new publication: Malinka C, Atkins J, Johnson M, Pernille Tønnesen P, Dunn C, Claridge D, Aguilar de Soto N, & PT Madsen (2020) "*An autonomous hydrophone array to study the acoustic ecology of deep-water toothed whales*." *Deep Sea Research I*. https://doi.org/10.1016/j.dsr.2020.103233 *Abstract of abstract:* - We developed an autonomous deep-water, large-aperture vertical hydrophone array using off-the-shelf components to address challenge of recording time-synchronised, high sample rate acoustic data at depth. - Array recordings can be used to quantify source parameters of toothed whale clicks. - We report on the design and performance of the portable and lightweight array. - Step-by-step directions on how to construct the array, as well as an analysis library for time synchronisation, are provided. *Abstract*: For vocal animals with distinctive calls, passive acoustic monitoring can be used to infer presence, distribution, and abundance provided that the calls and calling behaviour are known. Key to enabling quantitative acoustic surveys are calibrated recordings of identified species from which the source parameters of the sounds can be estimated. Obtaining such information from free-ranging aquatic animals such as toothed whales requires multi-element hydrophone arrays, the use of which is often constrained by cost, the logistical challenge of long cables, and the necessity for attachment to a boat or mooring in order to digitise and store multiple channels of high-sample rate audio data. Such challenges are compounded when collecting recordings or tracking the diving behaviour of deep-diving animals for which the array must be deployed at depth. Here we report the development of an autonomous drifting deep-water vertical passive acoustic array that uses readily available off-the-shelf components. This lightweight portable array can be deployed quickly and repeatedly to depths of up to 1000 m from a small boat. The array comprises seven ST-300 HF SoundTrap autonomous recorders equally spaced on an 84 m electrical-mechanical cable. The single-channel digital sound recordings were configured to allow for synchronisation in post-processing using an RS-485 timing signal logged by all channels every second. We outline how to assemble the array, and provide software for time-synchronising the acoustic recorders. To demonstrate the utility of the array, we present an example of short-finned pilot whale clicks localised on the deep-water (700 m) array configuration. This array method has broad applicability for the cost-effective study of source parameters, acoustic ecology, and diving behaviour of deep diving toothed whales, which are valuable not only to understand the sensory ecology of deep-diving cetaceans, but also to improve passive acoustic monitoring for conservation and management. Please get in touch for a PDF. Cheers, *Chloe Malinka* PhD Fellow Marine Bioacoustics Lab <https://marinebioacoustics.wordpress.com/> Dept. Biology, Aarhus University, Denmark. twitter: @c_malinka <https://twitter.com/c_malinka> email: chloe.e.malinka@gmail.com