Monitoring the dynamics and status of populations of harbor seals (Phoca vitulina richardii) requires efficient methods for estimating population parameters from mark–resight data. We used a test set of photographs from 182 individuals identified by flipper tags, scars, or unique pelage markings to test whether individuals could be identified accurately by their ventral pelage markings; to document efficiency and misidentification error rate associated with a computer-assisted photograph-matching system; and to test for bias in mark–recapture survival estimates resulting from misidentification errors. Pelage patterns of seals that were not of dark-intermediate or intermediate color phase were unique and stable from birth until 6–8 years, and from year to year as adults. The computer-assisted system greatly improved efficiency of photograph matching: 93.3% of good photographs and 69.9% of all photographs ranked 1st, and 95.2% of good photographs ranked in the top 0.3% of the ordered list for visual checking. Additional visual matching error averaged <3.0% for good photographs, and overall misidentification error rate was low at 1.8%, due to the availability of multiple photographs for matching. Inclusion of poor-quality photographs reduced ranking success by ∼20% and increased additional visual matching error up to 20%. Bias in survival estimates was −7.0% for a misidentification rate of 8.8%, but was ≤1.1% for misidentification rates of <2.7%, achieved by restricting data to only good photos. Our study suggests that estimation of misidentification error rate, inclusion of only high-quality photographs, or use of models that account for misidentification error, are required to prevent bias in mark–recapture survival estimates when using data from natural-marking studies.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.