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Sea lions and spotted owls

Recently we've started making headway on a contract to assess the risk to New Zealand sea lion (NZSL) populations on the South and Stewart Islands of New Zealand, from commercial fishing. A first stage has been to collate the available satellite tracking data for NZSL that have been tagged on these islands, to estimate their at-sea distribution. The biggest challenge is that relative few individuals have been tracked, all have been females, tagging has only happened at a small number of locations along a vast coastline, and the individuals were only tracked for a relatively short period of time (i.e., 6 weeks). Therefore, any distribution estimate is going to be extremely model-based, and rely on potentially untestable assumptions, which is never a great proposition. As part of the research we shall assess the sensitivity of the results to things such as the key assumptions of the modelling, and the influence of the data from certain individuals. Once this stage of the project is completed, we'll shall make recommendations on how to proceed.

In August Darryl was invited to attend a workshop on designing a range-wide sampling programme for the northern spotted owl (NSO) in the Pacific Northwest region of the USA. For the last couple of years, researchers at the US Forest Service and Oregon State University have been trialing the use of bioacoustic loggers to record calls of the NSO, and other species. A great deal of effort has been devoted to developing automated methods for extracting NSO calls from the recordings. Darryl was invited to provide expert input into possible designs from an occupancy modeling perspective, but also on general design principles as design. The 1.5 day meeting was held in Corvallis, Oregon, which meant the duration of Darryl's travel was about 4 times longer than the meeting! Despite that, the workshop was well worthwhile both in terms of the headway made towards an overall design, but also for Darryl to learn more about bioacoustic monitoring methods. He was surprised to learn that the researchers are confident of being able to identify individual birds from the recordings at some stage in the relatively near future, which would open up exciting possibility in terms of applying capture-recapture methods, in particular spatially explicit capture-recapture (SECR). With the rate of technological advancements, when designing long-term programmes it's important to not only consider what could be done with the current methods, but to also consider alternative ways in which the same raw data could be used. The potential for using SECR methods in the future will be kept in mind as this design process continues.

Finally, in a previous update we mentioned a paper Darryl was working on, looking at the impact of an earthquake on tree survival and growth. Well, the paper has now been published by the Journal of Ecology!

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