Adjusting survival estimates for premature transmitter failure: A case study from the Sacramento-San Joaquin Delta
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Abstract
In telemetry studies, premature tag failure causes negative bias in fish survival estimates because tag failure is interpreted as fish mortality. We used mark-recapture modeling to adjust estimates of fish survival for a previous study where premature tag failure was documented. High rates of tag failure occurred during the Vernalis Adaptive Management Plan’s (VAMP) 2008 study to estimate survival of fall-run Chinook salmon (Oncorhynchus tshawytscha) during migration through the San Joaquin River and Sacramento-San Joaquin Delta, California. Due to a high rate of tag failure, the observed travel time distribution was likely negatively biased, resulting in an underestimate of tag survival probability in this study. Consequently, the bias-adjustment method resulted in only a small increase in estimated fish survival when the observed travel time distribution was used to estimate the probability of tag survival. Since the bias-adjustment failed to remove bias, we used historical travel time data and conducted a sensitivity analysis to examine how fish survival might have varied across a range of tag survival probabilities. Our analysis suggested that fish survival estimates were low (95% confidence bounds range from 0.052 to 0.227) over a wide range of plausible tag survival probabilities (0.48–1.00), and this finding is consistent with other studies in this system. When tags fail at a high rate, available methods to adjust for the bias may perform poorly. Our example highlights the importance of evaluating the tag life assumption during survival studies, and presents a simple framework for evaluating adjusted survival estimates when auxiliary travel time data are available.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Adjusting survival estimates for premature transmitter failure: A case study from the Sacramento-San Joaquin Delta |
| Series title | Environmental Biology of Fishes |
| DOI | 10.1007/s10641-012-0016-3 |
| Volume | 96 |
| Issue | 2 |
| Publication Date | April 26, 2012 |
| Year Published | 2013 |
| Language | English |
| Publisher | Kluwer Academic Publishers |
| Contributing office(s) | Western Fisheries Research Center |
| Description | 9 p. |
| First page | 165 |
| Last page | 173 |
| Country | United States |
| State | California |
| Other Geospatial | Sacramento-San Joaquin Delta, San Joaquin River |
| Online Only (Y/N) | N |
| Additional Online Files (Y/N) | N |