A new study published in Ecological Applications demonstrates that commercial fisheries function much like an investment portfolio: diversity brings stability. The research shows that when different fish species in the Chesapeake Bay peak at different times, a dynamic known as "asynchrony," the overall fishery becomes more resilient and watermen are better protected from boom-and-bust cycles.
The research was led by former University of Virginia Ph.D. student and Virginia Sea Grant Fellow Sean Hardison and was based on data compiled by William & Mary's Batten School of Coastal & Marine Sciences and VIMS' Chesapeake Bay Multispecies Monitoring and Assessment Program (CHesMMAP) from 2002 to 2018, in addition to recorded values of commercial landings as documented by the Virginia Marine Resources Commission and Maryland Department of Natural Resources. The work brought together an interdisciplinary team of ecologists, economists and fisheries scientists from UVA, the Batten School & VIMS, the University of North Carolina at Chapel Hill, the University of Maryland Center for Environmental Science and Canada's Pacific Biological Station.
"The findings speak to how commercial fisheries benefit from natural fluctuations in the ecosystem, but also how these natural influences are mediated by factors like market prices and management practices," said Hardison, who is now a postdoctoral researcher at the University of Alaska Fairbanks. "The concept is similar to finance strategies that mitigate risk through a diversified portfolio of investments."
CHESMMAP monitors populations of juvenile-to-adult fishes from the head of Chesapeake bay at Poole's Island, Maryland, to the mouth of the Bay just outside the Chesapeake Bay Bridge Tunnel in Virginia. It is unique in that it tracks multiple fish species simultaneously, providing critical data that supports sustainable fisheries management and deepens understanding of the Bay's interconnected ecosystem. The researchers were interested in understanding the impacts of seasonal asynchrony among the bay's various commercially fished species on the quantity and economic value of fishers' landings, as well as the effects of different management practices between the states.
Different states, different dynamics
In Maryland, the commercial striped bass fishery is closed for part of the year to protect spawning stocks. That closure disrupted the natural asynchrony between fish populations and harvests, since striped bass dominate the commercial portfolio. While the closure encouraged watermen to target other species, which temporarily increased stability in landings, it did not stabilize revenue because the economic value of striped bass is far greater than other species in the fishery.
In Virginia, where no such closure exists, natural asynchrony initially provided a stabilizing effect. However, as the abundance of key species such as Atlantic croaker and spot declined between 2002 and 2018, harvests became less asynchronous and more volatile.
Hardison's former mentor and study coauthor Max Castorani, an associate professor in the Department of Environmental Sciences at UVA, said the findings illustrate how relying too heavily on a few high-value species such as striped bass can make a fishery portfolio unstable.
"Biodiversity doesn't just make ecosystems healthier, it makes them steadier over time," Castorani said. "It spreads risk and acts like insurance when certain fish are in short supply."
Christopher Patrick, an associate professor and ecologist at the Batten School & VIMS, added, "The most stable system would be one where you've got a lot of different species and they're all equally valuable. When you get an asymmetric value distribution, it kind of falls apart. This is what happens in Maryland to some extent."
One practical avenue for diversification highlighted in the study is the continuing development of a commercial fishery for invasive blue catfish in the Chesapeake Bay. While prices have historically been modest, the research suggests that even small price increases could spur significant additional harvest and market participation.
Broader significance
The study emphasizes the importance of viewing fisheries through both ecological and economic lenses. While biodiversity naturally contributes to stability, factors such as regulations, markets and fishing practices can amplify, or weaken, that benefit.
While the study focused on the Chesapeake Bay, the nation's largest and most economically important estuary, its findings can be applied broadly to fisheries around the world.
"Fisheries portfolios benefit from natural fluctuations in the ecosystem, but those benefits are mediated by management and human behavior" Hardison said. "Our research shows the ecological and economic benefits of biodiversity."
To read the study's full manuscript, visit Ecological Applications .
