Noble Hendrix¹ and Erica Fleishman²

¹QEDA Consulting
²Dept. of Fish, Wildlife and Conservation at Colorado State University
October 30, 2018 9:00 (PST): FSH 203

Modeling the spatio-temporal dynamics of one little bugger – delta smelt in the San Francisco Estuary

Delta smelt are an annual estuarine fish that complete their life-cycle in the San Francisco Estuary. They were listed as threatened under the Endangered Species Act in 1993 and have continued to decline since then. As a result, there is interest in determining how management of water flow through the estuary may affect the population dynamics of the species. Focus has turned to factors that affect survival and movement in the fall and in the spring, and here we are interested in evaluating the fall. We have constructed a spatially explicit model that estimates survival and movement as functions of covariates in four regions of the estuary. This framework allows an explicit examination of hypotheses regarding the role of environmental drivers on these processes. The model also includes the probability of capture for spatial replicates within each region. We have developed the model in Stan and have fit to simulated data with well-behaved statistical properties; however, the catch data are zero-inflated and over dispersed. We investigate several alternatives including zero inflated Poisson and zero inflated negative binomial for the likelihood and present the results of fitting several conceptual models developed from recovery plans. We are interested in evaluating approaches for model averaging and model goodness of fit. With respect to the latter, we are developing metrics that highlight spatio-temporal patterns in model weaknesses to help generate the next round of conceptual models.