Estimating current rates of increase and survival rates from reproductive data for dolphin populations in the eastern tropical Pacific

Dolphins are killed incidentally in the purse seine fishery for yellowfin tuna, Thunnus albacares, in the eastern tropical Pacific. Samples of the animals killed have been collected in order to estimate the vital rates of thevarious dolphin stocks which are affected. Numerous estimates of the reproductive rates for various stocks have been based on these samples (Perrin, et al., 1976, 1977a, b; Perrin and Henderson, 1979 ; Henderson, et al., 1979) but, at present, no estimates of survival rates are available. The age structure of a population is often used to provide estimates of survival (Seber, 1973), but the age structure of these samples of dolphins is not presently known. The purpose of this report is to point out that the reproductive structure (i.e. the proportion of individuals in different reproductive conditions) may contain implicit information on the age structure of a population and thus provide information on survival rates. 1983 NMFS (National Marine Fisheries Service) SWFSC (Southwest Fisheries Science Center) Library Public Domain 1930