Friday, November 30, 2012

Winter stats reading group starting up: Hierarchical Modeling and Analysis for Spatial Data

The NWFSC/SAFS stats reading group is reading "Hierarchical Modeling and Analysis for Spatial Data" by Banerjee et al. this quarter.  Fridays 3pm at SAFS 229 during Winter Qtr 2013.  Open to interested statistical ecologists.  Contact Eli.

Monday, November 12, 2012

New paper on spatial-temporal time series modeling

New paper just out by Eric Ward using Bayesian state-space time-series models.

"Applying time series models with spatial correlation to identify the scale of variation in habitat metrics related to threatened coho salmon (Oncorhynchus kisutch) in the Pacific Northwest"
Eric J. Ward, George R. Pess, Kara Anlauf-Dunn, and Chris E. Jordan
Canadian Journal of Fisheries and Aquatic Science (link to paper)

Abstract: Trend analyses are common in the analysis of fisheries data, yet the majority of them ignore either observation error or spatial correlation. In this analysis, we applied a novel hierarchical Bayesian state-space time series model with spatial correlation to a 12-year data set of habitat variables related to coho salmon (Oncorhynchus kisutch) in coastal Oregon, USA. This model allowed us to estimate the degree of spatial correlation separately for each habitat variable and the importance of observation error relative to environmental stochasticity. This framework allows us to identify variables that would benefit from additional sampling and variables where sampling could be reduced. Of the eight variables included in our analysis, we found three metrics related to habitat quality correlated at large spatial scales (gradient, fine sediment, shade cover). Variables with higher observation error (pools, active channel width, fine sediment) could be made more precise with more repeat visits. Our spatio-temporal model is flexible and extendable to virtually any spatially explicit monitoring data set, even with large amounts of missing data and no repeated observations. Potential extensions include fisheries catch data, abiotic indicators, invasive species, or species of conservation concern.