Precisely how is the estimate of number of days spent in the Salish Sea made for 2017 (Table Dataset_S1.xlsx)? Is it assumed that the observation effort is such that all whales present are observed, every day of the month? The 'occurrence' method used in previous publications uses a 6 day window to differentiate between occurrences of the same whale observed more than once. How then are some whales estimated to be present for only one day in Dataset_S1? From that table, the average proportion of the year spent in the Salish Sea is 0.04 for 2017. This is roughly what would be expected if whales were randomly, uniformly distributed across their range described in Ford et al. 2013. It seems therefore like the number of days may be biased low. Is my interpretation correct?