Partial Stratification in Two-Sample Capture-Recapture Experiments

• Activity Number: 646
• Type: Contributed
• Date/Time: Thursday, August 13, 2015 : 8:30 AM to 10:20 AM
• Sponsor: Section on Statistics and the Environment
• Author(s): Lasantha Premarathna* and Carl J. Schwarz
• Companies: Simon Fraser University and Simon Fraser University
• Keywords: Capture heterogeneity ; abundance ; survey-design and analysis

Abstract

Capture heterogeneity is known to case bias in estimates of abundance in two-sample capture-recapture (Lincoln-Petersen) experiments. Often this heterogeneity is related to observable fixed characteristics of the animals such a sex or size. If this information can be observed for each handled animal at both sample times, then it is straightforward to stratify (e.g. by sex) and obtain stratum-specific estimates. In many fishery experiments, it is more difficult, for example to sex all captured fish. In these cases, a sub-sample of the captured fish at each sampling occasion is selected and further, more costly, measurements are made.

In this talk we develop and apply new methods for these types of experiments. Furthermore, given the relative costs of sampling for a simple capture and for processing the sub-sample, optimal allocation of effort for a given cost can be determined. We also develop methods using Bayesian implementation to account for additional information (e.g. prior information about the sex ratio) and for supplemental continuous covariates such as length. These methods are applied to a problem of estimating the size of the walleye population in MilleLacs, MN.