A modeling and analysis tool, “artemis,” was developed to analyze quantitative Polymerase Chain Reaction data from environmental DNA studies. Artemis models were fit to data from two field experiments in a tidal environment (Shag Slough, San Francisco Bay-Delta, CA): Experiment 1) 54 live Delta Smelt were placed in a live pen and Experiment 2) 25 Delta Smelt and 15 steelhead were placed in a live pen. Water samples were taken prior to live pen deployment in both experiments, providing control samples that represented zero target fish in Shag Slough (this was confirmed by no detections of Delta Smelt or steelhead DNA in the control samples). The ln[eDNA] declined with distance of the sampling point from the live pen. Furthermore, DNA concentration in samples increased with increasing Delta Smelt-biomass level. The tool developed in this project, artemis, is effective for designing an eDNA study and analyzing the results: once a site has been characterized, artemis can be used to select the number of samples to be taken and the distribution of those samples through time to achieve a desired probability of DNA detection