Designing a shipboard line transect survey to estimate cetacean abundance off the Azores archipelago

Faustino, Cláudia E. S.; Silva, Mónica A.; Marques, Tiago A.; Thomas, Len

http://hdl.handle.net/10400.3/669

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Authors

Faustino, Cláudia E. S.

Silva, Mónica A.

Marques, Tiago A.

Thomas, Len

Abstract(s)

Management schemes dedicated to the conservation of wildlife populations rely on the effective monitoring of population size, and this may require the accurate and precise estimation of this parameter. Line transect distance sampling can be an effective approach for estimating abundance. Little information is available regarding cetacean abundance in the Azores. This paper had two aims: 1) to design a line transect shipboard survey to estimate the absolute abundance of the most common cetaceans off the Azores; and 2) to provide a set of potential survey effort scenarios to policy makers and environmental managers. Three survey scenarios are assessed, and one detailed survey design is presented. A total of 8,800 km of survey effort is recommended; at this level the expected coefficient of variation of estimates is less than 0.3 for most species. However, if logistic constraints prevent this, at least 5,000 km of survey effort should be used to achieve minimum sample size requirements; this is estimated to take 36 days of effort. It is also recommended to conduct a pilot survey. This would provide more detailed information that could be used to improve the survey design of what would be the first survey of this magnitude ever to be implemented in the Azores.