Capture–Recapture Studies Using Radio Telemetry with Premature Radio‐Tag Failure

Abstract

Summary. Radio-tags are often used in capture-recapture studies because of their high detectability. A key assumption is that radio-tags do not cease functioning during the study. Radio-tag failure before the end of a study can lead to underestimates of survival rates. We develop a model to incorporate secondary radio-tag failure data. This model was applied to chinook smolts (Oncorhynchus tshawytscha) on the Columbia River, WA.Estimates of fish survival from this model were much larger than those from the standard Cormack-Jolly-Seber analysis.

The Regional Salmon Outmigration Study--survival and migration routing of juvenile Chinook salmon in the Sacramento-San Joaquin River Delta during the winter of 2008-09

“…Statistical methods exist to correct survival estimates for tag failure (Cowen and Schwarz, 2005;Townsend and others, 2006), but our research indicates that these methods fail to completely remove the bias. These methods use the observed travel-time distribution to estimate the average probability of tag failure, which is then used to backcalculate true fish survival.…”

Summary of juvenile salmonid passage and survival at McNary Dam-Acoustic survival studies, 2006-09

“…Townsend and others (2006) found that adjusted survival estimates (0.9387) changed very little from the unadjusted estimate (0.9339) when the probability of a tag being operational at downstream detection arrays was high (>98). Cowen and Schwarz (2005) found that survival estimates that do not account for tag failure have potential to be biased, especially when failure rates exceed 10 percent. Our tag failure rates were between 1-5 percent for all fish except sockeye salmon in 2008 (which still had a tag failure rate well below 10 percent).…”

“…Cowen and Schwarz (2005) found that survival estimates that do not account for tag failure have potential to be biased, especially when failure rates exceed 10 percent. Our tag failure rates were between 1-2 percent for all fish so we feel that correcting the estimates using the tag life data would be inconsequential.…”

Estimating population size in the presence of temporary migration using a joint analysis of telemetry and capture–recapture data

“…We found no evidence for tag-induced mortality within the short period of our study. However, in longer-scale studies, it would be important to take tag-induced mortality, tag failure or rejection into account (Cowen & Schwarz 2005;McDonald, Amstrup & Manly 2003;Ward & David 2006). Additionally, not all sampling conditions are conducive to perfect radio-tag observation.…”