Researchers to Study Effects of “Dead Zone” on Gulf Shrimp Fishery

November 1, 2009
Contact:

Martin Smith, (919) 613-8028, marsmith@duke.edu; Lori Bennear, (919) 613-8083, lori.bennear@duke.edu; Kevin Craig, (850) 697-8550, kevin.craig@bio.fsu.edu

DURHAM, N.C. – Researchers from Duke University, Florida State University and the National Marine Fisheries Service have received a $702,700 four-year grant from the National Atmospheric and Oceanic Administration (NOAA) to study the effects of the increasingly severe seasonal “dead zone” in the Gulf of Mexico on the region’s shrimp fishery.

The dead zone, or hypoxic area, occurs every summer in coastal waters off Louisiana and Texas at the height of the Gulf shrimp fishery, one of the most valuable single-species fisheries in the United States.

Studies have linked the hypoxia to an oxygen-depleting algal bloom triggered by the flow of nutrient-rich runoff into the Gulf, much of it from farms in the Mississippi River watershed, which drains 41 percent of the continental United States. But little is known about its economic effects on the shrimp fishery.

The new study will be the first direct investigation of these links, says Martin D. Smith, associate professor of environmental economics at Duke’s Nicholas School of the Environment.

Smith and his colleagues received the $248,677 first-year installment of the four-year- grant from NOAA’s North Gulf of Mexico Ecosystem and Hypoxia Assessment Program (NGOMEX) earlier this fall.

“We hypothesize that hypoxia has substantial effects on the fishery harvest and profits,” Smith says, “and that these effects are mediated in large part by the spatial dynamics of the fishery.

“In other words,” he says, “we think that as the dead zone has grown larger and more severe, some of the shrimp and shrimping activity that used to occur in the affected area have moved to other areas. At the same time, changing economic conditions, including declines in real shrimp prices due to competition from imports and rising fuel costs, have likely influenced the shrimp fleet’s behavior.” All of these factors make it difficult to measure the dead zone’s impacts based solely on the reported size of annual shrimp harvests.

“An interdisciplinary project likes ours is necessary to determine the actual economic impact of the hypoxia, which may otherwise be underestimated or overestimated,” Smith says.

To produce a more accurate measure of hypoxia’s impacts over large spatial (1,000 kilometer) and temporal (decades) scales, the research team will collect and assess data from a variety of sources and models. They’ll analyze historical landings data, fishery surveys and independent surveys to determine the amount of shrimp and non-targeted by-catch species caught each year, and the time and distance boats traveled to catch them. Aerial surveys of shrimping activity in waters within 1,000 kilometers of the dead zone, conducted concurrently with regional mapping efforts, will further clarify the extent and nature of the fishery’s response to hypoxia. Econometric models will quantify the economic impact of hypoxia on the fishery within the context of current regulatory and global market pressures, while simulation models will be used to evaluate the potential effects proposed nutrient and fishery management policies might have on the fishery in coming years.

“Because the spatial extent and timing of the dead zone change each year, we can analyze fishery data as a natural experiment. The result of this experiment will tell us if hypoxia has contributed to declines in the Gulf of Mexico shrimp fishery,” Smith says.

Smith’s co-principal investigators on the study are J. Kevin Craig, assistant scholar scientist at the FSU Coastal and Marine Laboratory in St. Teresa, Fla.; Lori Snyder Bennear, assistant professor of environmental economics and policy at the Nicholas School; and Jim Nance, a shrimp biologist at the National Marine Fisheries Service in Galveston, Texas. Craig received his PhD in ecology from Duke in 2001 and served as assistant research scientist at the Duke University Marine Lab from 2002 to 2007.

Hypoxia, or low oxygen, occurs when dissolved oxygen in water drops below two milligrams per liter of water, the level necessary to sustain animal life. Hypoxic areas have increased in duration and frequency across Earth’s oceans since the 1900s.

The dead zone in the northern Gulf of Mexico is the second largest hypoxic area worldwide, and the largest one affecting a U.S. fishery. Annual mapping surveys indicate it can extend over areas up to 20,000 square kilometers, or roughly about the size of New Jersey.

By identifying the dead zone’s economic impacts on shrimpers, Smith says he and his colleagues hope “to bridge the gap” between federal and state agencies charged with managing nutrient loading from within the watershed, and those who manage coastal fishery resources.

“Our findings could give managers a quantifiable means to assess the EPA’s 2008 action plan to reduce the spatial extent of hypoxia in the Gulf,” he says. “We hope they also provide a better way to evaluate the likely impacts of nutrient loading and hypoxia on fisheries, the associated economic costs of habitat degradation, and the benefits of environmental policies to reduce nutrient pollution.”

The 2008 action plan is online at www.epa.gov/msbasin. For information about NOAA’s NGOMEX program, go to http://www.cop.noaa.gov/stressors/pollution/current/gomex-factsheet.aspx.


Editor’s note: For help reaching the researchers, contact Tim Lucas, (919) 613-8084,tdlucas@duke.edu

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