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NCCOS Project

Impacts of Hypoxia on Fish and Fisheries in the Northern Gulf of Mexico

This project began in January 2009 and was completed in December 2013

To protect fisheries and support ecosystem-based resource management in the northern Gulf of Mexico, we are developing modeling tools that will evaluate and simulate how large-scale changes in forcing factors (e.g., fishing pressure) affect the relative impact of hypoxia on living resources. The tools we are creating can also be used to evaluate alternative management outcomes for reducing hypoxia in the region.

Why We Care
The size and duration of hypoxia or dead zones in estuarine and coastal bottom waters has increased at an alarming rate for the past 20 years. This is a direct consequence of nutrient pollution. The resulting hypoxia kills some fish and squeezes others into small areas, where they are easy picking for predators.

The most well-known area of low dissolved oxygen and related problems occurs in the northern Gulf of Mexico and is commonly known as the “dead zone.”  Hypoxia in this zone strongly impacts pelagic food webs and fish production through several pathways, likely leading to changes in production potential (both positive and negative) of economically and ecologically important fishes.

What We Are Doing
We are developing quantitative tools to forecast the effects of hypoxia on the living resources in the northern Gulf of Mexico. Investigations focus on understanding and modeling the impact of hypoxia on fish production potential production in the northern Gulf of Mexico. We also want to know what will happen if nutrient discharges decrease. Can we predict how decreased size and/or shortened duration of the dead zone will affect fisheries?

We are using a variety of models, applying a multi-scale and multi-stressor approach to account for direct and indirect effects of hypoxia. Our focus is the ecosystem, which includes interactions between key organisms. Our models vary in complexity (individual to ecosystem level), size (near-field plume to fine-scale spatial pelagic to entire northern Gulf of Mexico), and time (hourly to inter-annual), and they are being used to understand and forecast management options and capabilities within the northern Gulf of Mexico community.

Combining models is helping us distinguish hypoxia-based effects from other effects, such as coastal land loss, commercial fishing, nutrient pollution, changes in coastal wetlands, and climate change (which is increasing the sea level). These stressors may impact fish production independently or in conjunction with hypoxia.

Questions we are addressing with this modeling approach include:

  • What is the effect of the spatial extent and seasonal timing of hypoxia on fish growth, recruitment and production potential?
  • How does hypoxia affect food web interactions in the pelagic zone?
  • How will hypoxia affect the spatial distribution and predator-prey interactions of mobile organisms and zooplankton?
  • How does hypoxia affect habitat quality and suitability for economically and ecologically important fishes?
  • How will management decisions on loadings affect fisheries through its impact on the timing and extent of hypoxia?
  • What is the potential of strong wind events (and their relationship to climate change) to re-aerate the water column and alter the interactions of fish and their prey?
  • What are the most effective tools to forecast food-web interactions, habitat suitability, and fish production in relation to hypoxia?

This work is part of the Gulf of Mexico Ecosystems & Hypoxia Assessment (NGOMEX) program.  The project team is led by Dr. Michael Roman of the University of Maryland Center for Environmental Science Horn Point Laboratory with co-investigators from the NOAA Great Lakes Environmental Research Laboratory, Oregon Sea Grant, Louisiana State University, Louisiana Department of Fishes and Wildlife, University of Michigan, and NOAA Fisheries.

Next Steps
We are comparing results with similar studies in the Chesapeake Bay and Lake Erie. These ecosystems are the second and third largest hypoxic areas in the United States, and we are using nearly identical field programs to assess them. Results from three field programs allow us to share and compare products, documents, model development, and results, including the effects of dead zones on pelagic food webs and fish production, across major ecosystems. The synthesis of predictive tools would add value across systems, and we’re planning connections with federal and state managers.

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