Quantifying Nursery Habitat Function: Variation in Habitat Suitability Linked to Mortality and Growth for Juvenile Black Drum in a Hypersaline Estuary

Abstract

The Black Drum Pogonias cromis population in the Upper Laguna Madre (ULM), Texas, USA, is known to exhibit regionally unique population dynamics and life history strategies in comparison with other populations. I examined regional variation in nursery habitat suitability for Black Drum on the Texas coast and further identified functionality of habitat variables in the ULM as it is related to the unique population dynamics observed in this bay system. Rank and relative importance of habitat variables for Black Drum in other regions of the Texas coast were found to differ from those for the ULM population. Furthermore, directionality of salinity and inlet distance differed in the ULM, indicating that increased recruitment in this system was tied to salinities greater than 40‰ and areas at the greatest distance from Gulf of Mexico inlets (i.e., Baffin Bay). Peak mortality and growth rates were found to occur at approximately the same mean salinity value (33‰), with decreases in both as salinity increased. Temperature and dissolved oxygen also exhibited quantifiable relationships with vital rates, although the salinity relationships were most striking. The relationship between growth, mortality, and CPUE suggested that observed recruitment of Black Drum in the ULM is a complex interaction between suitable habitat (hydrographic variables) and density dependence. The identification of regional variation in habitat relationships and the quantification of habitat functionality are crucial steps in interpreting population dynamics and formally incorporating such metrics into stock assessment. This movement from concept to quantification is key to making habitat protection and restoration a true priority in the fisheries management realm.

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

“…Demographic salinity model.-Vital rates are known to be intimately related to environmental conditions (Beck et al 2001). The uniquely hypersaline conditions in the ULM have been linked to YOY survival of black drum (Olsen 2019). I applied the structure of the demographic base model to changing YOY Z values across a range of salinities based on an analysis by Olsen (2019).…”

“…All parameter calculation, model construction, Figure 5. The modeled salinity-young-of-the-year mortality (Z) relationship calculated by Olsen (2019) and here used to model the impact of this relationship on overall population dynamics for black drum in the Upper Laguna Madre. Demographic model outputs are given for 25, 30, 35, 40, 45, 50, and 55 ppt. and model analyses were conducted in R (R Core Team 2016) using the "truncnorm" package to create truncated normal distributions for the Monte-Carlo approach (Trautmann et al 2014) and R base packages for all other model analysis (R Core Team 2016).…”

“…Increasing trends in both adult abundance and recruitment began in the early 1990s, which coincided with several other unique events including record drought conditions, winter freeze events, and the onset of a long-term algal bloom known as "brown-tide" that has since impacted the system (Buskey et al 2001;Wetz et al 2017). Calculated juvenile mortality is known to be lower in the ULM as compared to other Texas bays and density, mortality, and growth of juvenile black drum in this system has been linked to salinity (Olsen 2019). Further, black drum in the ULM are known to mature earlier than in other regions (Bumguardner et al 1996;Olsen et al 2018) presumably resulting in increased population fecundity.…”

“…Researchers often attempt to identify trends or optima of growth, survival, or abundance for various environmental parameters. Scharf (2000) and Olsen (2019) sought to recognize such correlates of growth and mortality among juvenile red drum (Sciaenops ocellatus) and black drum (Pogonias cromis), respectively. Similarly, Peterson et al (1999) examined salinity impacts on Atlantic croaker (Micropogonias undulatus) growth rates and Doerr et al (2016) conducted an in-situ experiment to determine optimum salinity preferences for juvenile white (Litopenaeus setiferus) and brown shrimp (Farfantepenaeus aztecus).…”

The Selection of Stocking Locations for Fisheries Enhancement in the Estuarine Environment: A Decision Support Tool

“…As such, it may increase both the survival and growth at early life stages (Beck et al 2001). Several studies have verified that such traits of viable nursery habitat do indeed act on recruits (Rooker et al 1998;Stunz et al 2002;Olsen 2019). Specific to the survival of stocked fish, the importance of selecting appropriate habitat locations is well documented Stunz and Minello 2001;Schlechte and Buckmeier 2006).…”