THERE ARE NO "MOST IMPORTANT" FISH IN THE SEA

 

Seventeen years ago, author H. Bruce Franklin published a book.  It was titled The Most Important Fish in the Sea:  Menhaden and America, and it caught the public’s attention.  A blurb advertising the book declares, in part, that

“…Today, one company—Omega Protein—has a monopoly on the menhaden ‘reduction industry.’  Every year, it sweeps billions of fish from the sea, grinds them up, and turns them into animal feed, fertilizer, and oil used in everything from linoleum to health food supplements.

“The massive harvest wouldn’t be such a problem if menhaden were only good for making lipstick and soap.  But they are crucial to the diet of bigger fish and they filter the waters of the Atlantic and Gulf coasts, playing an essential dual role in marine ecology perhaps unmatched anywhere on the planet.  As their numbers have plummeted, fish and birds dependent on them have been decimated, toxic algae have begun to choke our bays and seas.  In Franklin’s vibrant prose, the decline of a once ubiquitous fish becomes an adventure story, an exploration of the U.S. political economy, a groundbreaking history of America’s emerging ecological consciousness, and an inspiring vision of a growing alliance between environmentalists and recreational anglers.”

The book was very well written.  A lot of people read it, and a lot of people believed everything that Franklin wrote, even though he had no scientific background at all.  His academic degree was in English, which he first taught as an assistant professor, later associate professor, at Stanford University.  He was also something of a radical, who helped to set up a European network of deserters from the U.S. military during the Viet Nam war, founded a group that later became the Revolutionary Communist Party, and was ultimately fired from Stamford after inciting students to shut down the school’s computer facility and encouraging them to “resist police efforts.”

Both his lack of scientific training and his radical background arguably colored his book which, in my view, contained a few factual errors and definitely had anti-corporate undertones.  But those flaws seem to have only made some of his readers more fervent, and helped to create what I might deem “The Cult of the Menhaden,” a group of people who truly believe that menhaden really are “the most important fish in the sea,” and who are inclined to blame any decline in fish, bird, or marine mammal populations on a menhaden shortage, and then blame such alleged shortage in the menhaden reduction fishery, even though the last stock assessment, released three years ago, found that the Atlantic menhaden population is above the target reference point, and an October 2024 assessment revealed that the Gulf menhaden stock was also doing well.

Now, a new study recently concluded by The University of Southern Mississippi, which was funded by the Science Center for Marine Fisheries, may finally help at least some of those people place menhaden in their proper ecological context, which is best described in the header of the school’s press release announcing the study's findings:

“What Do Gulf Predators Really Eat?  Groundbreaking Study Finds Menhaden Play a Smaller Role Than Expected.”

That conclusion probably doesn’t come as a surprise to fishermen who’ve spent much time on the water, and realize that predators can’t choose to be picky.  Most are opportunists that will feed on whatever might be around at the time, whether that forage is mullet, river herring, Atlantic herring, pilchards, bay anchovies, various species of shad, shrimp, mackerel, juvenile weakfish or bluefish, menhaden, or anything else. 

Menhaden, with their big, splashy, surface-hugging schools are often the most obvious baitfish, particularly on the inshroe grounds, and fish feeding on menhaden can be extremely easy to catch, but neither of those things has any real bearing on menhaden’s actual importance as forage.

Yet, fueled by “the most important fish in the sea” distortions and the continuing availability of foundation and other grants that support well-publicized anti-menhaden industry campaigns, far too many people have come to believe that menhaden have a disproportionately large impact on coastal ecosystems

The University of Southern Mississippi study will hopefully bring a few more facts—and hopefully a bit of rationality—to what has become an emotion-driven menhaden debate.

What the Mississippi scientists did was take a long look at what fish in the Gulf of Mexico were actually eating.  They employed a two-pronged approach, which combined the analysis of hundreds of stomach-content studies dating back as far as the 1950s with stable isotope analysis of fish’s tissue samples, which provide a definitive look at what fish are eating.

The press release described isotope analysis this way:

“Stable isotopes are heavier forms of elements, like carbon and nitrogen, that are present in all species and at all points in the food web.  Because these isotopes do not decay, they accumulate in predator species in different proportions, depending on the diet of the predator.  By analyzing the levels of stable carbon and nitrogen isotopes in predator species, the study authors are able to determine what types of diet sources the predators generally rely on, as well as what trophic level they predominantly feed on.  This technique offers a much broader view of predator diets than stomach content analysis alone.

“’When an animal eats a prey item, there is a differential uptake in the carbon and the nitrogen,’ said Dr. Kevin Dillon, another author of the study and a Associate Professor at the University of Southern Mississippi’s Gulf Coast Research Laboratory.  ‘So, we can measure those small differences to try to piece this together and look at each organism’s trophic position within that food web.  So, we’re able to tell from a fish’s isotopic signature whether the fish was eating phytoplankton or if it was eating another fish that had eaten phytoplankton.’”

So, what did the study reveal about the importance of menhaden in the Gulf food web?

“’We looked at some 30-plus predator species, many of them exceptionally well-studied.  We did not find any single species where we would say Gulf menhaden were the most important fish in their diet,’ said Dr. Robert Leaf, one of the authors of the study and Director of the School of Ocean Science and Engineering at the University of Southern Mississippi.

“’When you look at the information that we have, what we find is that Gulf menhaden are a prey item—certainly they play a role in the trophic dynamics of predators—but not to the extent of other prey items, which are also very important—in fact, more important,’ Dr. Leaf continued…

“The scientists found that species like red drum, summer [sic] flounder, and spotted sea trout are general, opportunistic feeders that do not rely solely on a single prey species.  Instead, their diets vary depending on factors such as seasons, prey availability, and other climactic conditions.

“Species like Gulf menhaden are important parts of the diet, but there is no single prey species that these predators overwhelmingly rely on.  There is no ‘most important’ prey species in the Gulf.  [emphasis added]”

The Cult of the Menhaden, and particularly its ministers and ecclesiastics—that is, public relations flaks and consultants—who are paid to proselytize and spread the faith, will undoubtedly reject the study’s conclusions, as cults always reject truths that conflict with dogma.

And it is always possible that the study’s conclusions won’t be transferrable to the Atlantic menhaden that inhabit waters off the East Coast; Atlantic coast ecostems and habitats aren’t the same as those in the Gulf, and many East Coast species engage in much longer seasonal migrations than are typical of spotted sea trout or drum.  It’s not inconceivable that menhaden are more important there.

But anyone who has ambushed striped bass in coastal creeks, when the fish follow spring alewife runs; who has fished the August “whitebait” runs at Montauk; who has frozen their hands in the post-Thanksgiving cold, when bass blitzed on Atlantic herring, understand that striped bass, like the predators in the Gulf, are opportunistic predators.  Anyone who has ever cut open a bass, to find a gut filled with flounder, blackfish (tautog), black sea bass, scup, mantis shrimp, squid, mackerel, crabs, or a host of other creatures knows that the fish’s diet extends far beyond menhaden.

And anyone who has gutted a bluefish, weakfish, summer flounder, or just about any other East Coast predator knows that they are also not fussy eaters, but opportunistic predators that will feed on whatever is slow enough to catch and small enough to fit between their jaws.

So, there’s a pretty good chance that the findings of the Gulf study will be relevant to the East Coast as well.

None of this means that the menhaden isn’t important.  To the contrary, the menhaden is unquestionably an important forage fish, one of a number of important forage fish on the Atlantic and Gulf coasts.

None of this means that menhaden can’t, in certain places and at certain times, be the dominant forage species, and that a local decline in menhaden abundance can’t harm local ecosystems, although there remains insufficient evidence to say, with anything approaching certainty, that such harm really occurs.

And none of this means that menhaden shouldn’t be carefully managed, that conservative quotas shouldn’t be imposed, or that scientists shouldn’t expend serious effort looking into the question of localized depletion, and whether it really exists.

All of those things matter, and should be pursued.

But the results of the University of Southern Mississippi menhaden study debunk the notion that menhaden are “the most important fish in the sea,” and sharply undercut the Cult of the Menhaden’s dogma.  And it is more than past time to put such dogma aside and, whether managing menhaden or any other fish, allow good science and good data, rather than myth and emotion, prevail.