2012 COURSE DATES: AUGUST 4 – 17, 2012 - Sirenian International

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IUCN Red List because it is a small and declining population without ongoing, effective
conservation actions (Self Sullivan et al. 2011). These data provide confirmation of the
appropriateness of the current IUCN status and highlight the need to improve our ability to
establish the magnitude of decline.
Extending our study to 15 years considerably improves our ability to detect a
population trend. Over a study duration of 15 years, we would still have a limited ability to
detect slight and moderate declines, but our index and protocol can detect precipitous
declines within the benchmarks established in the Marine Mammal Protection Act, the
IUCN Red List (Taylor et al 2007) and other publications. Taylor et al. (2007) defined a
precipitous decline in marine mammal abundance as a 50 percent decline after 15 years
because a 50% decline over this period would result in a stock being classified as
“depleted” under the MMPA. Under the IUCN Red List guidelines, a decline of this
magnitude could result in a status designation anywhere between “vulnerable” to
“endangered” depending on initial population size, cause, certainty and the reversibility of
the decline (IUCN 2010). IUCN Red List guidelines establish level of endangerment –
nearly threatened to critically endangered – based on declines of 10 – 90% over 10 years or
3 generations (whichever is longer), depending on initial population size, cause, certainty
and the reversibility of the decline (IUCN 2010). Bart et al. (2004) recommended a
standard for landbird surveys of an 80% power to detect a 50% decline over 20 years.
Similarly, Hatch (2003) recommended a standard for counts of colonial seabirds of a 90%
power to detect a 50% decline over 10 years. Using this sampling regime over a 15 year
time interval, we would have a power of 11%, 51% and 100% to detect slight, moderate or
precipitous declines. All of our survey protocols had 100% power to detect 50% declines
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