Using spatial capture-recapture methods to estimate long-term spatiotemporal variation of a wide-ranging marine species

Determining population status to inform mitigation of anthropogenic threats requires statistical approaches that investigate spatial and temporal variation. In the face of climate change, it is increasingly important to differentiate between changes in population size and redistributions of populations. This is especially true for wide-ranging species such as the blue whale. An abundance of eastern North Pacific blue whales has previously been estimated using (non-spatial) closed capture-recapture and distance sampling methods, but the estimates show opposite and diverging trends over the last 30 years. Evidence that the distribution has been expanding could explain the apparent disparity, due to the confounding effects of spatial variation in sampling and the changing distribution. To investigate this, we apply, for the first time, spatial capture-recapture (SCR) methods to blue whale photo-identification data from small boat surveys to estimate abundance. The study area was defined as..., , # Using spatial capture-recapture methods to estimate long-term spatiotemporal variation of a wide-ranging marine species

Dataset DOI: [10.5061/dryad.wh70rxx13](10.5061/dryad.wh70rxx13)

## Description of the data and file structure

These data relate to spatial-capture recapture modelling of eastern North Pacific blue whale abundance as described in the associated paper (Whittome et al. 2025). Photo-identification data were collected by the Cascadia Research Collective. These data were then processed for input to the R package secr (Efford 2024) to conduct spatially-explicit capture-recapture modelling. The data input files and model run code are provided. The data input files only contain summarised location information of whale encounters. A grid (with a cell size of approximately 44km) was applied to an area which spanned the extent of the encounters, and the centroid of each grid cell was considered the ‘trap’ with encounters allocated to the closest trap (see associated publicati...,