Southern flounder paralichthys lethostigma hereafter flounder are an important FIN fish in coastal waters of texas the populations have been drastically declining since the 1990S which has prompted…

The Texas Parks and Wildlife Department received a $153,546 Formula Grant from the U.S. Fish and Wildlife Service (USFWS) under the State Wildlife Grants (SWG) Program (CFDA 15.634), awarded January 1, 2026, with completion anticipated December 31, 2027. This award supports the development of bioenergetics modeling (BEM) for southern flounder (Paralichthys lethostigma), a commercially and recreationally important finfish species experiencing significant population declines in Texas coastal waters since the 1990s. The project employs process-based ecological modeling to elucidate the mechanisms underlying flounder growth and population dynamics, moving beyond correlative approaches to enable managers to accurately predict how environmental changes—such as temperature fluctuations and shifting prey availability—will affect survival, growth, and recruitment in both natural and hatchery settings.

The project generates theoretical growth curves derived from laboratory-based bioenergetics modeling that integrate intrinsic physiological parameters (temperature and mass-dependent respiration and consumption rates) with extrinsic environmental variables (water temperature and prey availability). These models are validated against existing empirical growth data and inform evidence-based management decisions for both hatchery operations and wild stock management. A sub-award of $153,546 was issued to the University of Texas at San Antonio (UTSA) to develop the southern flounder bioenergetic models, leveraging the institution's research capacity to advance species conservation objectives aligned with Texas's Wildlife Action Plan priorities.

Southern flounder paralichthys lethostigma hereafter flounder are an important FIN fish in coastal waters of texas the populations have been drastically declining since the 1990S which has prompted research on flounder biology to understand population dynamics and develop hatchery production protocols to augment natural recruitment consequently managers now have considerable knowledge of survival growth recruitment and reproduction among many other aspects of flounder biology much of this knowledge has been elucidated by observing patterns and hypothesizing the underlying mechanisms that generate such patterns IE correlative approach for example individual growth rates differ among populations and these differences have been attributed to differences in temperature and prey availability because the underlying mechanisms are uncertain managers are challenged with predicting how environmental changes in hatcheries or in nature will affect survival growth and recruitment thus process based as opposed to pattern based correlative approaches are needed to elucidate the ecological mechanisms that underlie patterns so environmental changes can be accurately predicted bioenergetics modeling hereafter BEM is one such approach that uses a daily energy balance equation to predict individual growth based on the difference between energy loss via respiration and energy gain via consumption inputs for BEM include intrinsic parameters IE temperature and mass dependence of respiration and consumption that are species specific and extrinsic parameters IE water temperature and prey availability that vary spatially and temporally the output of BEM is a theoretical growth curve that can be compared to the wealth of existing empirical growth data bems developed for other species have informed hatchery operations and wild stock management and also have forecasted impacts of environmental change including rising temperatures and shifting prey bases this project will use laboratory assays to measure the intrinsic BEM parameters for post metamorphic age 0 flounder validate growth projections from bems using the wealth of estuary temperature and flounder growth data collected by texas parks and wildlife department hereafter tpwd since the 1980S and produce high resolution maps of flounder growth potential across all texas estuaries under present day and future climate scenarios these bems will also provide hatchery operators with new and detailed data on thermal optima forage energy use efficiency and growth