Reduced Mississippi river flow weakened the base of the marine food web, triggering cascading fishery losses
A severe and prolonged U.S. drought in the late 1980s played a central role in one of the largest fisheries declines ever recorded in the Gulf of Mexico, according to a new study published in Nature Communications.
The research, led by scientists at the University of Haifa and co-authored by Ben Kirtman , a climate scientist and dean of the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science, found that drought-driven reductions in Mississippi River flow sharply limited nutrient delivery to coastal waters.
"Our findings show that the fisheries collapse was not driven by fishing pressure alone," said Igal Berenshtein, head of the Marine Ecology and Ocean Health Laboratory at the University of Haifa, and the study's lead author. "The prolonged drought reduced river discharge and nutrient input to the Gulf, weakening phytoplankton production and primary productivity at the base of the food web. That disruption cascaded through the ecosystem, ultimately reducing fish biomass and fisheries yields."
The study documented a roughly 42 percent drop in total fish biomass and a 34 percent decline in fisheries catch following the drought period. Nearly 90 percent of species groups examined showed decreases in biomass.
The Gulf ecosystem depends heavily on nutrients delivered by the Mississippi River to sustain commercially important species. One of the hardest-hit species was Gulf menhaden, a key forage fish that supports the region's largest fishery by landings and provides essential prey for predators such as mackerel, tuna, sharks, marine mammals and seabirds.
"Our results demonstrate how climate extremes on land can directly affect marine food production," Kirtman said. "As droughts become more frequent and intense under climate change, the risks to seafood supply and coastal economies increase."
Using a Gulf-wide ecosystem model, researchers projected that under high greenhouse gas emission scenarios, fisheries biomass could decline by approximately 60 percent by mid-century and more than 70 percent by the end of the century if severe drought conditions persist.
The findings highlight growing food security concerns. The Gulf supports one of the nation's most productive fisheries, supplying seafood to domestic and international markets.
"Managing fisheries in a changing climate will require accounting for shifts in temperature, rainfall, river flow, nutrient delivery, and ecosystem productivity," Kirtman added. "Adaptive strategies that incorporate climate variability will be essential to sustaining fisheries over the long term."
The study titled " Historical depletion and future drought-driven risks to Gulf of Mexico fisheries production " was published February 9, 2026 in the journal Nature Communications. Funding for the study was provided by RESTORE grant # NA17NOS4510098 and Gulf Research Program of the National Academies of Sciences, Engineering, and Medicine under award number 10000883
The authors include Berenshtein, Kirtman, Kim de Mutsert of the Division of Coastal Sciences at the University of Southern Mississippi, and David D. Chagaris from the Nature Coast Biological Station at the University of Florida.
About the University of Miami and Rosenstiel School of Marine, Atmospheric and Earth Science
The University of Miami is a private research university and academic health system with a distinct geographic capacity to connect institutions, individuals, and ideas across the hemisphere and around the world. The University's vibrant academic community comprises 12 schools and colleges serving more than 19,000 undergraduate and graduate students in more than 180 majors and programs. Located within one of the most dynamic and multicultural cities in the world, the University is building new bridges across geographic, cultural, and intellectual borders, bringing a passion for scholarly excellence, a spirit of innovation, and a commitment to tackling the challenges facing our world. The University of Miami is a member of the prestigious Association of American Universities (AAU).
Founded in 1943, the Rosenstiel School of Marine, Atmospheric, and Earth Science is one of the world's premier research institutions in the continental United States. The School's basic and applied research programs seek to improve understanding and prediction of Earth's geological, oceanic, and atmospheric systems by focusing on four key pillars:
*Saving lives through better forecasting of extreme weather and seismic events.
*Feeding the world by developing sustainable wild fisheries and aquaculture programs.
*Unlocking ocean secrets through research on climate, weather, energy and medicine.
*Preserving marine species, including endangered sharks and other fish, as well as protecting and restoring threatened coral reefs. www.earth.miami.edu .
