Mark-recapture modeling accounting for state uncertainty provides concurrent estimates of survival and fecundity in a protected harbor seal population

Harbor seal breeding behavior and habitats constrain opportunities for individual-based studies, and no current estimates of both survival and fecundity exist for any of the populations studied worldwide. As a result, the drivers underlying the variable trends in abundance exhibited by harbor seal populations around the world remain uncertain. We developed an individual-based study of harbor seals in northeast Scotland, whereby data were collected during daily photo-identification surveys throughout the pupping seasons between 2006 and 2011. However, a consequence of observing seals remotely meant that information on sex, maturity-stage, or breeding status was not always available. To provide unbiased estimates of survival rates we conditioned initial release of individuals on the first time sex was known to estimate sex-specific survival rates, while a robust design multistate model accounting for uncertainty in breeding status was used to estimate reproductive rate of multiparous and 3-yr-old females. Survival rates were estimated at 0.95 (95% CI = 0.91-0.97) for females and 0.92 (0.83-0.96) for males, while reproductive rate was estimated at 0.89 (0.75-0.95) for multiparous and 0.69 (0.64-0.74) for 3-yr-old females. Stage-based population modeling indicated that this population should be recovering, even under the current shooting quotas implemented by the recent management plan.