Citation:

Hagy, Jim, R. Fulford, D. Secor, E. Niklitschek, T. Amidon, AND I. Park. Effects of dissolved oxygen and water temperature on Atlantic sturgeon in the Delaware River. Coastal & Estuarine Research Federation Conference, Portland, OR, November 12 - 16, 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 will share information about why the model was developed, and how it can be used to better understand potential effects of management actions to address low dissolved oxygen in the context of environment climate change.  The presentation will be directed toward a technical audience as expected at a scientific conference.

Description:

We combined an existing bioenergetics-based model of juvenile Atlantic sturgeon growth with an empirical survival model to predict the effect of dissolved oxygen (DO) and water temperature on instantaneous potential production of juvenile Atlantic sturgeon, an oxygen-sensitive anadromous fish species. Although once abundant, the Delaware River Atlantic sturgeon population is at critically low levels, reflecting combined effects of historical overfishing followed by water quality degradation. We applied the model to data from several continuous water quality monitoring sites in the Delaware River and to conditions predicted using a coupled Environmental Fluid Dynamics Code – Water Quality Analysis Simulation Program (EFDC-WASP) water quality model. Although the cohort model is based in laboratory experiments, model predictions of fish size are consistent with sizes observed during fish surveys. Simulated survival explains order-of-magnitude interannual differences in annual catch per unit effort (CPUE) from juvenile abundance surveys in 2009-2022. The cohort model outperforms simpler correlations between CPUE and DO alone in part because it considers the strong interaction between the effect of DO and water temperature on growth and mortality. The EFDC-WASP model shows that ammonium discharges to the river are a significant cause of low oxygen in the river and that substantial DO increases would result from reducing discharges under the most critical low-flow conditions. The cohort model predicts that these improvements would result in a large increase in growth and survival of Atlantic sturgeon in the Delaware River in years when currently survival is minimal.  The largest improvements are predicted in the vicinity of Marcus Hook, PA, an area of the river that has been used preferentially by Atlantic sturgeon, while smaller improvements are also expected farther upstream, where a region with reduced oxygen is expected to remain in some years even after wastewater upgrades. Results from the cohort model suggest that water quality improvements would increase prospects for Atlantic sturgeon population recovery, potentially reducing the risk of extinction, but also that any increase in peak summer water temperature associated with climate change could pose an additional threat to population recovery.

URLs/Downloads:

Record Details: