Salinity tolrerance of brown mussel Perna perna (L.) from the gulf of mexico: an extension of life table analysis to estimate median survival time in the presence of regressor variables

摘要

The nonindigenous brown mussel Perna perna was first recorded in the Gulf of Mexico at Port Aransas, Texas in 1990. The association between survival time and chronic exposure to hypo- and hypersaline conditions was examined to estimate the potential range of habitats that P. perna could invade in coastal North American Gulf of Mexico habitats. A novel application of the discrete logistic failure time model (DLFTM) was used to estimate covariate-adjusted median survival times from the interval-level survival data collected. This method allowed factorial-type comparisons of the covariate-adjusted medians across treatments. This analysis indicated that salinities ranging from 15-50 ppt were nonlethal to P. perna, under whihc at least 80% of individuals survived 30 dyas (720 h). Chronic exposure tosalinities outside 15-50 ppt were lethal to perna. Lethality was size-dependent, with both smaller and larger individuals having reduced survival times. For an average-sized individual (shell length = 40 mm), median survival times were 191, 268, 335, 119, and 116 h at 0,5,10,55, and 60 ppt, respectively. The 15-50 ppt incipient salinity limits of Texas P. perna suggest that this species could potentially colonize the majority of marine and estuarine coastal habitats in the Gulf of Mexico.