A line transect method to estimate abundance of long-diving animals

Abstract

Long-diving marine mammals, such as sperm whales and Baird's beaked whales are frequently missed in line transect sampling even though they are on the trackline. The methods so far developed to estimate the proportion of animals missed on the trackline are complicated or sensitive to model assumptions. A simpler model is developed in the present study. The model requires an estimate of mean surfacing rate that is independent of the line transect survey and does not require any complicated survey design and non-robust parameters, such as scan rate of the binoculars of observers. In addition, it can flexibly take account of systematic heterogeneity using covariates. The abundance is estimated using the Horvitz-Thompson estimator. The simulation test showed that the proposed method is promising.