Stenella longirostris: Braulik, G. & Reeves, R.: The IUCN Red List of Threatened Species
The Spinner Dolphin is one of the most abundant cetaceans globally (Perrin 2018). The sum of existing abundance estimates is more than one million dolphins, and as these estimates are from only a small fraction of the total distribution range of the species, total abundance is presumably much higher. The Eastern Spinner Dolphin population was listed as Vulnerable on the IUCN Red List in 2012 (http://www.iucnredlist.org/details/133712/0); it suffered large mortality in tuna-purse seine fisheries in the past, and is no longer thought to be declining but has shown no clear signs of recovery. Some island-associated populations of Spinner Dolphins are small, insular, and vulnerable to disturbance and other threats. Spinner Dolphins are taken throughout much of their range as bycatch in fisheries and as direct targets of hunting in some areas. There is little quantitative information on bycatch rates in most range states, but it is clear that as well as being one of the most abundant cetaceans, the Spinner Dolphin is one of the more frequently bycaught species. Direct removals are substantial in a few areas, notably the Solomon Islands (average of 214 spinners per year 2000-2002). The species was classified as Data Deficient (DD) on the IUCN Red List in 2008 and it remains data-poor in much of its range. However, given its generally high abundance and pan-tropical distribution, and in the absence of evidence that threats are significant throughout the species’ extensive range, the Spinner Dolphin is assessed as Least Concern. There is not enough information to determine whether the global population has declined by 30% or more over three generations (therefore qualifying for listing as Vulnerable) but this is possible.