Development of an Atlantic sturgeon cohort model for the tidal-fresh Delaware River
Citation:
Hagy, Jim. Development of an Atlantic sturgeon cohort model for the tidal-fresh Delaware River. Water Quality Advisory Committee of the Delaware River Basin Commission, West Trenton, NJ, March 23, 2023.
Impact/Purpose:
An oxygen sag attributable to oxygen consuming waste loads has been present in the tidal fresh reaches of the Delaware River for decades. The oxygen sag reached its peak magnitude in the 1950s and 1960 before beginning a long recovery which has been linked to reductions in pollutant loads. With continued water quality improvements in the river, EPA determined in 2022 that oxygen levels sufficient to support propagation of oxygen sensitive species in the river were attainable and that DO criteria for the river must be revised to support maintenance and propagation of migratory fish. An important aspect related to the task of criteria development is identifying dissolved oxygen levels that would support propagation of Atlantic sturgeon (Acipencer oxyrichus oxyrrichus), a fish listed as endangered under the Endangered Species Act. This presentation outlines a model that was developed and applied as a tool to translate observed or simulated water quality in the Delaware River into expected growth and propagation of juvenile Atlantic sturgeon. The presentation, to be made to the Delaware River Basin Commission's Water Quality Advisory Committee, will explain the development of the model and draft results from its application. The information presented may result in additional interest in the further development and application of the model.
Description:
A cohort simulation model was developed to predict the growth and survival of Age-0 juvenile Atlantic sturgeon in the Delaware River based on water quality conditions in the river. The model utilizes a bioenergetics model predicting daily instantaneous growth rate of juvenile Atlantic sturgeon as a function of salinity, water temperature and dissolved oxygen. Daily instantaneous mortality rate is predicted based on water temperature and dissolved oxygen. The model simulates growth and survival of Atlantic sturgeon from July 1 through November 30. The model was applied to predict growth and survival for 2010-2022 using water quality data from two continuous water quality monitoring stations on the Delaware River, Penn's Landing and Chester, PA. The model was also applied to 3 scenarios of model output from an EFDC/WASP water quality simulation model developed by the Delaware River Basin Commission. Simulations predicted growth of fish to the same size range as fish captured in the river and correctly predicted many of the years in which catch per unit effort of young-of-the-year juveniles in abundance surveys was high and low. Simulations predicted that current DO levels cause significant mortality and impair growth of juveniles. A management scenario proposed by the Delaware River Basin Commission would result in a substantial increase in juvenile growth and survival, while not fully eliminating impairment due to low DO. Spatial simulation results show that cohort growth and survival in Zone 3 of the river and near Penn's Landing is lower than in Zone 4 and near Chester, PA, and that reduced ammonium nitrogen loading to the river will likely result in larger improvements in growth and survival near Chester, PA than further upriver.
