Seeing Red and Finding Fraudulent Fish

Peter B. Marko wanted his marine biology graduate students to be able to do DNA fingerprinting of tissues. So, he gave them the assignment of analyzing 22 samples of red snapper meat from fish retailers in eight states. The students extracted DNA from each piece of fish, copied it so there would be enough material to analyze, then matched the DNA in each batch against an archived map of the genes from a confirmed member of the species, Lutjanus campechanus.

Marko had expected his class to turn up a mislabeled fish or two, maybe. “But we were really shocked to find that three-quarters of the fish weren’t red snapper,” he told Science News Online. Although the Western Atlantic hosts a number of related snappers, U.S. law prohibits the marketing of any fish other than L. campechanus as red snapper.

In the July 15 Nature, the researchers report that on the basis of DNA analyses, five of the frauds appear to be related species—vermilion and lane snappers, probably from the Western Atlantic, and crimson snapper from the Indo West Pacific. However, Marko notes, for roughly a third of the analyzed fish, “we really can’t identify their species at all”— their DNA has never been logged into any of the libraries of genes in commercially important fish.

“That worries us,” Marko says, “because it might mean that there are fish being caught, sold, and consumed that we know very little about—and that aren’t being monitored carefully.” The problem is compounded by the facts that fish stocks around the world are in danger and the demand for seafood is steadily increasing (SN: 7/26/03, p. 59: Catch Zero).

Marko says his new findings suggest that true red-snapper stocks might have been so depleted that fleets are now surreptitiously substituting other species for this high-value reef fish. This could have “serious conservation implications,” Marko says. If red snapper stocks are more depleted than regulators realize, then this species may need extra protection from fishing—something fleet owners might not want to acknowledge.

However, the new data could reflect fraud not at the fisheries level, but among fish wholesalers or retailers. Grocers or their suppliers could be mislabeling substitutes for the increasingly costly and hard-to-get red snappers. This risks sending consumers and government officials dangerous signals about the health of the fishery, says Marko. As the campaign to give swordfish a break pointed out a few years ago (see A Grilling Analysis), a fishery sometimes needs a chance to rebound.

Reduced swordfish consumption from 1998 to 2000 indeed contributed to the recovery of North Atlantic swordfish populations, notes Ellen K. Pikitch, executive director of the Pew Institute for Ocean Science at the University of Miami’s Rosenstiel School. She says that the swordfish recovery “is one of the few success stories in fisheries management.”

Holistic oversight

The problem with red snapper, notes Joey Ritchie Brookhart of the Seafood Choices Alliance in Washington, D.C., is that the species is “overfished.” The federal government has imposed fishing regulations to help the species recover, she notes, “but what’s also happening is that juvenile red snapper are being taken as bycatch in some of the shrimp fisheries.”

This is a case, she told Science News Online, in which “you’re trying to do your best and yet another [fished species] is potentially obstructing the recovery of red snapper.”

Three organizations—the Blue Ocean Institute, Environmental Defense, and the Monterey Bay Aquarium—have put together recommended lists of fish that diners should “enjoy” or “avoid.” Red snapper is on the latter.

According to a statement from the Monterey Bay Aquarium, “There has been an overall decline in snapper populations, since these fishes are generally caught faster than they can reproduce. . . . International snapper fisheries generally have poor management plans, if they have management plans at all. For these reasons, red and vermilion snapper and imported snapper of all varieties are on our ‘avoid’ list.”

Traditionally, Pikitch observes, governments have managed fish populations species by species. This approach ignores the fact that species don’t live alone, but as parts of large, interrelated ecosystems. As stocks of one species diminish, commercial fleets turn to—and sometimes overharvest—other populations, which may be what’s happening in the red snapper fishery of the Western Atlantic.

In the July 16 Science, Pikitch and her coauthors argue for overhauling fisheries management to account for this interrelatedness of marine organisms. For many years, Pikitch notes, the North Atlantic swordfish long-line fishery caught, killed, and wasted six sharks for every swordfish it hauled in.

Even though the sharks were considered “junk fish” with little or no commercial value, they were more devastated by fishing than prized swordfish were. The reason is that, whereas male swordfish mature in a year and females by age 5, sharks don’t typically mature until age 10, 15, or 20 (SN: 5/1/99, p. 280).

Moreover, the typical female swordfish broadcasts tens of thousands of eggs into the water at a time, and hundreds of fertilized eggs can hatch within a year. A shark, in contrast, typically produces just two to six live pups at a time, with gestation lasting up to 2 years.

The devastation of sharks in the North Atlantic is a classic example of the toll of bycatch. At a minimum, bycatch amounts to huge quantities of aquatic protein accidentally being destroyed. At worst, it can compromise the very survival of vulnerable fish communities, notes Pikitch.

As an example of the latter, she points to the case of the common skate (Raja batis) in the Irish Sea. Skates, which resemble rays, are essentially flattened sharks with wings. The graceful common skate took its name from its former abundance in European waters. With few natural predators, the species can take a full decade to reach sexual maturity, by which time it tips the scales at some 100 pounds.

Although fishing fleets had never targeted the common skate, the large animal often ended up as bycatch for trawlers seeking other bottom-dwelling fish, such as sole and mackerel. Eventually, as trawling off Ireland killed skates faster than they could reproduce, the species “ended up disappearing from an entire sea,” Pikitch says. It was gone from the Irish Sea by the 1970s.

The lesson of all such stories, she and her colleagues argue in the new Science paper, is that fishing should be managed within the context of an entire ecosystem—paying special attention to the most vulnerable species within it. Even if they have no commercial value, such species could play an integral role in the marine food web and so need to be preserved.