ASMFC In The News
Republished from the Chesapeake Bay Journal
A widely publicized study pointing to a shortage of Atlantic menhaden as the cause of osprey nest failures in the Chesapeake Bay has come under fire from a trio of Virginia fisheries scientists.
The study, published in January by researchers with the College of William & Mary’s Center for Conservation Biology, linked a drastic decline in osprey reproduction in Virginia’s Mobjack Bay with a drop in the availability of menhaden, the migratory fish that once made up the bulk of the birds’ diet. They said ospreys are having fewer young and more chicks are dying in the nest for lack of food than in decades past. They suggested that the commercial menhaden harvest be limited to sustain ospreys, also known as fish hawks.
That research report, written by center director Bryan Watts and five co-authors, gave credence to complaints by conservationists and sports anglers about large-scale commercial menhaden harvests in the Bay. Those groups have long contended that a Virginia-based fishing fleet operated by Omega Protein has been depleting menhaden stocks in the Chesapeake, depriving Atlantic striped bass and other fish of a vital source of forage.
The commercial menhaden harvest in the Bay has been capped since 2006 at 51,000 metric tons, but conservationists and recreational anglers argue that the cap does not leave enough of the fish in the Chesapeake to sustain species that feed on them. Lacking firm evidence, they have failed so far to convince fishery managers to ban or further reduce large-scale commercial menhaden harvests in the Bay.
Prompted in part by the center’s study saying ospreys are suffering from a menhaden shortage, the Atlantic States Marine Fisheries Commission, which regulates near-shore fishing from Maine to Florida, formed a work group in September to weigh new “precautionary” harvest limits.
In October, though, Frontiers in Marine Science, the same journal that published the osprey paper, carried a critique of it by Professor Robert LaTour and two other researchers at the Virginia Institute of Marine Science, another division of William & Mary.
LaTour and his colleagues — associate research scientist James Gartland and assistant research scientist Gina Ralph — faulted the data and statistical methods used in the center’s study. They disputed the conclusion that ospreys’ nesting woes could be attributed to a decline in the menhaden population.
They wrote that “while we share concerns about the demographic and foraging trends of osprey in Mobjack Bay, the analyses presented in [the study] do not establish a clear relationship with menhaden abundance and availability.”
LaTour said he felt compelled to take issue with the study because its conclusions had been widely shared and fishery managers were being pressed to act based on it.
“Once you release results as [Watts] did with press releases, you can’t really unring the bell,” LaTour said.
The VIMS scientists don’t challenge the center’s findings that osprey reproduction has declined, but they disagree with the way the bird biologists assessed trends in the number of menhaden frequenting Mobjack Bay. There aren’t any surveys of menhaden there that go back to the 1970s, when the Center for Conservation Biology began tracking osprey nesting. So, the center’s researchers used a coastwide index of menhaden abundance that was based on surveys conducted by multiple states over that time period. The critics contend that the coastwide index couldn’t accurately reflect localized variations in menhaden populations.
Watts acknowledged that a coastwide menhaden population index was not the best yardstick of abundance in Mobjack Bay.
“I didn’t like it, either,” he said. But with no long-term surveys of menhaden in Mobjack that go back that far, Watts continued, “I felt like we were using the best data available.”
Watts said he doesn’t disagree with some of the criticism from the VIMS scientists. But, notwithstanding the flaws they cited in the statistical analysis, Watts insisted that the center’s field observations of osprey nests over time had shown that the adult birds were catching fewer menhaden to feed their chicks and fewer young birds were surviving.
“Scientists disagree all the time,” he said. “But when you back away from the details here, it really doesn’t change [the fact that] osprey chicks are starving in the nest because there aren’t enough menhaden to support them.” While osprey do feed on other fish, he said, few are as nutritionally rich as menhaden.
Watts broadened the center’s osprey study beyond Mobjack Bay in 2024, working with scientists from the U.S. Geological Survey to follow breeding in 12 locations around the Chesapeake. That fieldwork found similarly poor reproduction in 10 sites along the Bay’s mainstem, where menhaden typically can be found, while osprey pairs produced more young in two freshwater areas where they feed on different fish.
LaTour said he doesn’t doubt that there are fewer menhaden in the Bay for ospreys to feed on, but he said the evidence is lacking to pin that on the Omega Protein fishing fleet. He suspects instead that there’s been a change in the distribution of menhaden in the Chesapeake. He noted there have been likely climate-induced shifts seen in the distribution of other fish populations along the Atlantic coast.
On one thing, LaTour and Watts completely agree — the need for more focused data on menhaden abundance in the Chesapeake. At the request of Virginia lawmakers, LaTour and other VIMS scientists drew up a plan in 2023 for conducting such a study, but the General Assembly put off deciding until 2025 whether to fund it.
Omega Protein, which also participated in the planning for the study, said it had no hand in blocking legislative action. At a processing plant in Reedville, VA, the Canada-based company converts menhaden caught in the Bay and along the mid-Atlantic coast into pet food and nutritional supplements. Omega has long enjoyed legislative support, and it has resisted any further catch restrictions, citing a 2022 finding by the Atlantic States commission that the coastwide menhaden population is not overfished.
Industry defenders of Omega point out that Maryland’s annual survey of juvenile fish found more young menhaden in the upper Bay in each of the last two years than have been seen since 1990. Those little fish, spawned in the ocean, spend most of their first year in the Bay but head back to sea in the fall, returning as adults the following spring. Ospreys tend to prey on fish larger than those “young of year” visitors, studies have shown.
The Atlantic States commission workgroup that is studying whether new menhaden harvest limits are warranted in the Bay or elsewhere reported in late October that it likely would need until spring to conclude its deliberations.
“They’re searching for science-based information to allow them to formulate those recommendations,” LaTour said, “but the reality is that information is a long way away.”
Watts vowed to keep digging to find out what is happening with the Bay’s ospreys. He said he plans to expand the field study further in 2025.
“One thread doesn’t make a tapestry,” he said. “You can’t see the whole picture.” But if researchers keep collecting data, Watts concluded, “the picture will become clearer over time.”