Evaluating methods for estimating mortality from acoustic telemetry data

Abstract

Mortality rates are major determinants of long-term sustainability of exploited fish populations, yet accurately estimating these rates can be challenging. We used simulations to evaluate nonspatial and spatial modeling approaches for estimating mortality rates from acoustic telemetry detection data. Data were generated assuming different receiver configurations (grids, lines), number of receivers, and mortality levels. Relative error rates for total mortality ranged from 0% to 83% for the nonspatial model and from 1% to 141% for the spatial model. Absolute error rates ranged from 0.00 to 0.11 for the nonspatial model and from 0.01 to 0.15 for the spatial model. Accuracy and precision in mortality estimates were sensitive to assumed mortality rates and receiver configurations; the high-density receiver grid resulted in the lowest error rates. Estimates were consistently positively biased. We recommend using grid receiver configurations for mortality rate estimation from acoustic telemetry studies. The potential for biased mortality estimation from acoustic telemetry detection data should be considered during study design, particularly for those species with behavior and ecology that may result in long periods without detection.