The challenge of monitoring coastal marine mammals

Marsh, Helene;Brooks, Lyndon;Hagihara, Rie

Abstract

Monitoring trends in the distribution and abundance of coastal marine mammals is challenging because their detectability below the water surface is variable and they are highly mobile, generally occupying vast areas. These attributes diminish the precision and accuracy of abundance estimates, both of which are essential to detect trends and trigger management actions. However, many survey techniques are available that improve the precision and accuracy of abundance estimates by explicitly accounting for the factors that influence our ability to spot individual animals during surveys. This chapter demonstrates two approaches that account for such biases by using strip transect sampling and mark–recapture surveys to estimate the abundance of dugongs and coastal dolphins in northern Australia. Although these approaches require considerable ecological knowledge, a high level of technical expertise and significant resources, they provide the best estimates of abundance to date for these species. Nonetheless, trend detection is still difficult given the current survey frequency and precision of the abundance estimates.

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Monitoring Threatened Species and Ecological Communities.

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978-1-4863-0771-5

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CSIRO

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Melbourne, VIC, Australia

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