Summary
The scope of this document is model-based estimation of abundance (and its uncertainty) from counts of cetaceans obtained using standard distance sampling line transect surveys (e.g., Buckland et al., 2015). The aim is not to be prescriptive about what the actual model formulation is but rather provide guidelines on what modellers can do to ensure reliable results and how they can show that this is the case to readers. Though it is the case that we wish to build models to relate counts to environmental covariates (most importantly space), the commonly seen case of estimating and interpreting effect sizes and associated relationships is ignored here. Here we are only interested in estimating abundance (Nˆ), its variance (VarNˆ) and potentially covariances between temporally separate estimates of abundance, usually as a function of spatial location.