Salinity tolerance 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

The nonindigenous brown mussel Perna perna was first recorded in the Gulf o f Mexico at Port Aransas, Texas in 1990. The association between survival t ime and chronic exposure to hypo- and hypersaline conditions was examined t o estimate the potential range of habitats that P. perna could invade in co astal North American Gulf of Mexico habitats. A novel application of the di screte logistic failure time model (DLFTM) was used to estimate covariate-a djusted median survival times from the interval-level survival data collect ed. This method allowed factorial-type comparisons of the covariate-adjuste d medians across treatments. This analysis indicated that salinities rangin g from 15-50 ppt are nonlethal to P. perna, under which at least 80% of ind ividuals survived 30 days (720 h), Chronic exposure to salinities outside 1 5-50 ppt were lethal to P. perna. Lethality was size-dependent, with both s maller and larger individuals having reduced survival times. For an average -sized individual (shell length = 40 tnm), median survival rimes 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 specie s could potentially colonize the majority of marine and estuarine coastal h abitats in the Gulf of Mexico.