Intrinsic growth (rmax) and generation time (T) estimates for the cetacean genera Sousa, Orcaella, and Neophocaena, in suport of IUCN red list assessments

A workshop was held May 20 – 21, 2015, in San Diego, California, USA, titled: “Workshop to Assess/Re-Assess IUCN Red Listings for Indo-Pacific Species of Coastal Marine Small Cetaceans.” Species included were Orcaella brevirostris, O. heinsohni, Neophocaena asiaeorientalis, and two of the three Indo-Pacific Sousa species: S. chinensis and S. plumbea. Sousa sahulensis and Neophocaena phocaenoides were not assessed, largely for lack of information about these species. Red List assessments require estimates of generation time for a pristine population, i.e., one with stable age structure and abundance at carrying capacity such that the annual per-capita population growth rate isλ=exp(r)=1. Let this generation time be denoted T0. Estimating T0 for the above species is the primary goal of this analysis. Additionally,this analysis provides point estimates of the anthropogenic mortality rate required to reduce a population by 30%, 50%, or 80% over three generations (3T0). These reductions warrant Vulnerable, Endangered, or Critically Endangered status, respectively, under the Red List criterion A; IUCN 2012).