Research that touches on menhaden in the Chesapeake Bay has long been contentious, because it helps inform how officials choose to regulate the controversial fishery.
The latest disagreement is playing out in scientific literature. Three scientists at William & Mary’s Virginia Institute of Marine Science, which conducts research for state regulators, recently published a formal critique of a study linking declines in the local osprey population to the menhaden industry.
The study they critiqued came from another arm of William & Mary: the Center for Conservation Biology, which studies birds.
The center has monitored ospreys for years. Director Bryan Watts said they’ve now seen the birds struggling to reproduce for more than a decade.
His team published a study earlier this year recording the lowest number of osprey chicks since the 1970s. They said the baby birds are dying of starvation, and posit that’s because there aren’t enough menhaden for them to eat.
In their new critique of that study, the VIMS scientists say there’s simply not enough data to make that claim.
“It may turn out that the linkage is real, and I'm certainly willing to admit that, but right now I just don't feel like we can say that,” said Rob Latour, a professor who has long studied menhaden.
Latour said he respects his William & Mary colleagues’ research on osprey, and VIMS is also concerned about the struggling population.
But he felt compelled to write the commentary after seeing members of the public use the study to ask for changes in policy.
“There was so much pressure being put on industry and policymakers to make decisions, and the scientific basis for doing that was not very solid at all,” he said. “So the point of the commentary was to give an alternative perspective.”
Menhaden are a keystone species in the bay, a nutrient-dense food source for species including osprey and striped bass.
The menhaden reduction industry — of which only one company, Omega Protein, is left in Virginia — harvests the fish to turn into fish oil for products like supplements and pet food.
There is a long-running battle in Virginia over how to manage the fishery – and the lack of data about the species is now front and center.
Many environmental groups and recreational anglers have been pushing Virginia to ban industrial menhaden fishing in the Chesapeake Bay, claiming overharvesting is impacting the ecosystem.
Omega Protein, which runs a plant in Reedville, says there’s no evidence backing up those concerns, pointing to federal surveys finding the overall East Coast menhaden population is healthy.
But critics say the coastwide data could obscure a decline happening specifically in the Chesapeake Bay, and want research to find out.
A bill to do so was tabled by Virginia’s General Assembly at the most recent session.
Watts, the osprey researcher, agrees that more data is needed to support his work. But he feels in order to get to the bottom of the issue and save osprey, they have to use what is currently available in the meantime.
Latour disagrees.
“Once you establish a linkage and claim that there is this causal mechanism, you can't unring that bell,” he said. “To me, the prudent thing is to follow what the science says and stop where the science is uncertain.”
Latour said menhaden are uniquely difficult to study because they “do not lend themselves well to traditional fishery survey gear.” Scientists have to use expensive equipment like spotter planes, large vessels and underwater acoustic monitoring.
Researchers need to get a lot more information to assess whether the fish are struggling in the bay – and how much the industry is to blame versus other causes, he said. Warming waters due to climate change, for example, have begun driving some fish populations north.
Watts said his team is working to systematically eliminate other factors that could be behind the birds’ decline.
“As we continue to collect data the preponderance of evidence gets louder and louder and the picture becomes more clear,” he said. “It’s pretty clear in terms of what the osprey have to say, that menhaden are not in sufficient numbers to support the current population. And to me, that's unequivocal at this point.”
But “scientists disagree all the time, and there’s nothing wrong with that.”
