We are developing a model to forecast striped bass recruitment in the Chesapeake Bay and are partnering with NOAA's National Marine Fisheries Service to incorporate the model in fish stock assessments and fisheries management decisions. Unlike other models, ours accounts for weather and climate variability, as well as fishing pressure. We issued accurate forecasts in 2009, 2010, and 2011.
Why We Care
Commercial fishing landings in the Chesapeake Bay region contributed $908 million to the economy between 2000 and 2004 (Kirkley et al., 2005). One study estimated that in 2004 Virginians benefited from $1.23 billion in sales, $717 million in income, and more than 13,000 jobs associated with recreational and commercial fishing (Lellis-Dibble et al., 2008).
In 2009, President Obama acknowledged that this productivity is threatened and issued Executive Order 13508, Chesapeake Bay Protection and Restoration, to strengthen and coordinate federal initiatives addressing challenges facing the bay and watershed. Our striped bass forecast addresses three goals of the executive order:
- Provide habitat research to protect and restore Chesapeake Bay living resources and water quality
- Respond to climate change in the Chesapeake Bay watershed
- Strengthen science and decision support for ecosystem management in the Chesapeake Bay and its watershed.
What We Are Doing
We are improving striped bass management by providing information to decision makers on effects of natural (e.g., climate) and human-induced (e.g., fishing) changes on population numbers. How many striped bass can be removed from Chesapeake Bay under different environmental conditions? What are the consequences of future climate change to Chesapeake Bay striped bass? Fishery management generally ignores these types of questions due to the uncertainty in predicting effects of environmental variability on fish populations. Our research answers these questions and improves management of Atlantic coast striped bass.
We are developing more accurate striped bass forecasts as a tool for fisheries management in the Chesapeake Bay. Unlike previous models, ours links weather effects to striped bass population numbers, explaining environmental “noise” and reducing uncertainty. Models inputs include freshwater flow and temperature and other weather and climate data acquired from the U.S. Geological Survey and NOAA’s National Climatic Data Center.
What We Are Finding
We found strong evidence that climate is driving the dramatic changes in striped bass population levels in the Chesapeake Bay. We found that wet years are associated with good striped bass reproductive success, whereas dry years are associated with poor reproductive success. Freshwater flow from rivers affects the amount of zooplankton prey available to young striped bass, and striped bass survival is enhanced in wet years when prey levels are high. We detected a threshold in flow between 60,000 and 70,000 cubic feet per second; striped bass survival and subsequent numbers are highest when flows exceed this threshold.
Natural resource managers are more likely to use models that provide accurate forecasts and can be explained using simple scientific principles. We are validating these models using a combination of statistical approaches and field studies to “ground truth” model predictions and the mechanisms used to explain how and why our models work. They provided accurate forecasts for the number of young striped bass for 2006, 2007, and 2009.
As resources become available, we will continue to validate our upper Chesapeake Bay striped bass model and develop a baywide model expanding our forecast coverage to include the entire Chesapeake Bay. This tool has important implications for Atlantic coast fisheries because Chesapeake Bay supplies more striped bass to the Atlantic coast population than any other spawning location.
We will be integrating our findings into the Atlantic States Marine Fisheries Commission stock assessment and evaluating the usefulness of this research for water resource management decisions. The evaluation is a timely consideration because most of the freshwater entering Chesapeake Bay flows through the Conowingo Dam, and the 30-year relicensing of this facility is scheduled for 2014.
Also, we are continuing to work with climatologists and hydrodynamic modelers to evaluate the use of downscaled global climate forecasts. The global climate model is run by the International Research Institute (IRI) at Columbia University and is being downscaled for the Chesapeake Bay region by our partners at the Earth System Science Interdisciplinary Center at the University of Maryland. Seasonal projections may improve lead time of our recruitment forecasts by up to one year before the fish being observed in Chesapeake Bay.
Finally, we will use the approach we developed for striped bass as a prototype to develop models for other Chesapeake Bay and Atlantic coast fishery resources.