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

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.

Regional Variation in Growth and Mortality of Spotted Seatrout in the Western Gulf of Mexico

“…With that said, body size is a function of age as well as genetics and nutrition, and it is also clear that southern estuaries in Texas harbor relatively older populations of Spotted Seatrout. In a related fashion, habitat availability and quality are known to impact vital biological rates, such as growth and mortality (Beck et al 2001), which can further impact population demographics (Levin and Stunz 2005;Olsen 2020). The high relative growth of individuals observed on the northern coast is likely offset by the relatively low mortality of those on the southern coast, possibly caused by variation in suitable habitat availability and variation in predation and fishing pressure among estuaries.…”

Importance of Serpulid Reef to the Functioning of a Hypersaline Estuary

“…Salinity conditions in the Upper Laguna Madre, including Baffin Bay, are on average hypersaline (mean ± standard deviation = 35.9 ± 7.0; Montagna et al 2011). Salinity in Baffin Bay specifically is generally higher and has more spatiotemporal variability (2013-2016Montagna et al 2018) than the Upper Laguna Madre as a whole -2017Breaux et al 2019).…”

“…In these situations, Serpulid reefs are the primary source of macrofauna prey. An increased understanding of the P. cromis diet is important because up to 76% of annual commercial landings for the region are harvested from Baffin Bay (Olsen et al 2018), and because periodic emaciation events with significantly underweight P. cromis have plagued this relatively small estuarine system (Olsen 2014;2016). Additional research to estimate P. cromis population size and carrying capacity would help further elucidate the importance of Serpulid reef macrofauna to maintaining fish populations in Baffin Bay.…”