QUANTIFYING HABITAT CONCEPTS: POPULATION IMPACTS OF STAGE-SPECIFIC SALINITY RELATIONSHIPS FOR BLACK DRUM (POGONIAS CROMIS) IN THE UPPER LAGUNA MADRE, TEXAS USA

Abstract

Abstract Environmental factors can often have population effects on aquatic organisms, though studies of environmental effects are often specific to a given life stage. Stage-structured demographic models provide a means of exploring the multivariate suite of life history parameters associated with a population and can provide a tool for understanding population-wide impacts of single stage events (e.g., mortality and fecundity). Here, the unique dynamics observed for an isolated population of black drum (Pogonias cromis) and the population-wide impacts of salinity as a driver of young-of-the-year (YOY) survival were investigated. This modeling exercise revealed that the dynamics observed in the black drum population are potentially driven by increased survival in the post-settler/YOY stage and that this increased survival is at least partially a result of the higher salinities that typify the Upper Laguna Madre of Texas, a hypersaline estuary (34% increase in population growth rate across the range of salinity examined). Early maturation in this population was also shown to have the potential to provide infrequent, large pulses of fecundity to the population. Quantifying the population-wide impact of such drivers can place management decisions into the context of the environment and provide both a proof-of-concept for specific management action and realistic expectations for managers and constituents alike. Without such formal quantification, it will be difficult for habitat concepts to move from an abstract management tool to widespread application.