DURHAM, NC – To reduce commercial fishing’s impacts on ecosystems and fisheries productivity, many experts in recent years have advocated for increased selectivity in the size and species of fish that can be harvested.

But a new “Policy Forum” analysis published today in Science by an international team of researchers suggests it may be time to rethink this approach.

Utilizing a ‘balanced harvest’ approach to fishing – in which moderate levels of mortalities are distributed proportionately over the widest possible range of species, stocks and sizes in an ecosystem – could mitigate adverse effects and address food security better than increased selectivity, the researchers argue.

“Increasing evidence suggests traditional selective fishing approaches might not protect ecosystems and fisheries as intended, and may in fact make them more vulnerable to large changes in structure and function,” says Daniel Dunn, a PhD student in the Marine Geospatial Ecology Lab at 91’s Nicholas School of the Environment.

Dunn, who is stationed at the 91 Marine Lab in Beaufort, N.C., is one of 18 authors of the new analysis.

In theory, increased selectivity helps prevents growth overfishing – the loss of future yields if juveniles before they are allowed to reproduce – and reduces by-catch of non-targeted species.  But by synthesizing data across ecosystem models from 30 fisheries worldwide, the researchers found that these benefits occur only at levels of fishing mortalities so low that yield in the fishery is not economically sustainable.

In contrast, they found compelling evidence that when fishing is spread over more functional groups and sizes, yields are higher and harmful impacts, such biomass depletions and extinctions of local populations, are lower across a broad percentage of system removals – or roughly, total catch as a proportion of total biomass.

“Balanced harvesting is a selective approach to fishing, but it broadens the selectivity perspective from scales of fishing operations and stocks to the integrated scale of ecosystem productivity and impacts,” Dunn says.

In their analysis, the researchers propose that ecosystem modeling could help determine appropriate patterns of fishing mortality and selectivity, allowing managers to set sustainable limits for catch sizes and total removals – including discards, not just landings.  In a system where each component of the ecosystem is utilized in appropriate amount, by-catch of non-targeted fish species would become part of the management strategy.  Market incentives could be developed to promote the increased use of these traditionally less-utilized species as animal feed or for human consumption.

Issues regarding the potential benefits and implementation of balanced harvesting remain, the researchers write, “However, consideration of food security and minimizing ecosystem impacts suggests that the time has come to take action.”

In addition to Dunn, authors of the new article are from the International Union for Conservation of Nature Commission on Ecosystem Management’s Fisheries Expert Group (Belgium); the IUCN Global Marine Program (Switzerland); the University of Bergen (Norway); the Department of Fisheries and Oceans (Canada); L’Institut Francais de Recherche pour l’Exploitation de la Mer (France); CSIRO Marine and Atmospheric Research (Australia); Tokyo University of Marine Sciences and Technology (Japan); the Danish National Institute of Aquatic Resources; FishFix (Belgium); the Bedford Institute of Oceanography (Canada); the Inter-American Tropical Tuna Commission (United States); International Institute for Applies systems Analysis (Austria); the Institute of Marine Research (Norway); the University of York (United Kingdom); the Fisheries Research Agency (Japan); and the Institute for Marine Resources and Ecosystems Studies (the Netherlands).