title: Bayesian spatiotemporal analysis of zero-inflated biological population density data by a delta-normal spatiotemporal additive model.
abstract: We evaluate the spatiotemporal changes in the density of a particular species of crustacean known as deep-water rose shrimp, Parapenaeus longirostris, based on biological sample data collected during trawl surveys carried out from 1995 to 2006 as part of the international project MEDITS (MEDiterranean International Trawl Surveys). As is the case for many biological variables, density data are continuous and characterized by unusually large amounts of zeros, accompanied by a skewed distribution of the remaining values. Here we analyze the normalized density data by a Bayesian delta-normal semiparametric additive model including the effects of covariates, using penalized regression with low-rank thin-plate splines for nonlinear spatial and temporal effects. Modeling the zero and nonzero values by two joint processes, as we propose in this work, allows to obtain great flexibility and easily handling of complex likelihood functions, avoiding inaccurate statistical inferences due to misclassification of the high proportion of exact zeros in the model. Bayesian model estimation is obtained by Markov chain Monte Carlo simulations, suitably specifying the complex likelihood function of the zero-inflated density data. The study highlights relevant nonlinear spatial and temporal effects and the influence of the annual Mediterranean oscillations index and of the sea surface temperature on the distribution of the deep-water rose shrimp density.
authors.affiliation: Dipartimento di Scienze economiche e metodi matematici, Università degli studi di Bari Aldo Moro, Largo Abbazia Santa scolastica 53, 70124 Bari, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Arcuti
authors.affiliation: Dipartimento di Scienze economiche e metodi matematici, Università degli studi di Bari Aldo Moro, Largo Abbazia Santa scolastica 53, 70124 Bari, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Pollice
authors.affiliation: Dipartimento di Scienze economiche e metodi matematici, Università degli studi di Bari Aldo Moro, Largo Abbazia Santa scolastica 53, 70124 Bari, Italy.
authors.forename: Nunziata
authors.initials: N
authors.lastname: Ribecco
authors.affiliation: Dipartimento di Biologia, Università degli studi di Bari Aldo Moro, Via E. Orabona 4, 70125 Bari, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: D'Onghia
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D003445:Crustacea; D015233:Models, Statistical; D009792:Oceans and Seas; D011156:Population Density; D062211:Spatio-Temporal Analysis; D013696:Temperature
keywords: Bayesian analysis; Biological population dynamics; Generalized additive models; MCMC; Zero-inflated data