Abundance Estimation

We review the main methods for estimating the abundance of marine mammal populations. Shipboard and aerial surveys often use line-transect methods (a variety of distance sampling), and these are described in detail. We also consider another distance sampling method, cue counting. Although it is not currently widely used, we expect that it will see increasing use for analyzing acoustic survey data. Mark–recapture methods are also described. Again, we expect renewed interest in these methods, because spatially explicit capture–recapture methods offer a new and flexible way of analyzing acoustic survey data conducted using fixed sensors. Migration counts are addressed briefly, and the use of colony counts to assess pinniped populations is described.