TY - JOUR

T1 - Mark-recapture modelling accounting for state uncertainty provides concurrent estimates of survival and fecundity in a protected harbour seal population

AU - Cordes, Line S.

AU - Thompson, Paul

PY - 2014/4

Y1 - 2014/4

N2 - 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.

AB - 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.

KW - vital rates

KW - population dynamics

KW - demography

KW - Phoca vitulina

KW - photo-identification

KW - individual-based

U2 - 10.1111/mms.12070

DO - 10.1111/mms.12070

M3 - Article

VL - 30

SP - 691

EP - 705

JO - Marine Mammal Science

JF - Marine Mammal Science

SN - 1748-7692

IS - 2

ER -