Life table analysis of long-lived marine species with implications for conservation and management

Many long-lived marine species have been overexploited through intentional or incidental harvest. Whales, sharks, sea turtles, and large marine fishes have a wide range of life history strategies. We compared the life tables of several species by converting them to age-based matrix models and calculating the proportional contribution of newborn, juvenile, and adult annual survival to population growth (lambda, where In(lambda) = r, the intrinsic rate of increase). This comparative analysis, called elasticity analysis, has been used to compare life histories and set management priorities for threatened species. Long-lived marine species have very low fecundity and first-year survival elasticities, while the relative contribution of juveniles or adults depends on age at first reproduction. Small decreases in sensitive adult or large juvenile age-classes can drastically reduce population growth rates and are unlikely to be compensated for by an increase in newborn production or survival. We illustrate the potential use of life table elasticity analysis with case studies for sea turtles and sharks. Although deterministic models are rarely used in fisheries, we suggest that elasticity analysis can provide valuable insight for predicting the effects of fishing mortality on various life histories.