Shell Trade Threatens Chambered Nautilus, Agency Says

Palau nautilus from side. Palau, Micronesia. (Photo credit: Lee R. Berger)

WASHINGTON (CN) – Noting that “hundreds of thousands” of nautilus shells are traded yearly, the National Marine Fisheries Service has proposed the chambered nautilus for Endangered Species Act listing. The listing proposal is in response to a petition filed by the Center for Biological Diversity last year.

“This is great news, particularly given this administration’s recent string of listing denials. The chambered nautilus needs protection from the international shell trade,” CBD’s oceans program director Miyoko Sakashita said. “The Endangered Species Act offers the best chance this ancient creature has of avoiding extinction.”

The agency says it is proposing to list the nautilus as a threatened species under the ESA due to the relentless pressure on the species from the international shell trade, which covets the nautilus’ unusual large coiled shell for collectors and for use in jewelry and trinkets, causing the species to decline in fished areas to the point of local extinction in some cases.

Overharvesting is complicated by the nautilus’ own life history factors. Nautiluses are related to squid and other octopods, and have been traced back relatively unchanged for 500 million years in the fossil records. They are long-lived animals that may not become reproductively mature until they are 17 years old, and produce only 10-20 eggs per year with a 1-year incubation period. Therefore, the species is slow to adapt and does not bounce back quickly even when fishing is stopped.

The agency also considers the species to be an “extreme habitat specialist” because it cannot tolerate temperatures above “approximately 25°C [77°F] or depths exceeding around 750-800 meters. At depths greater than 800 m, the hydrostatic pressure will cause the shell of the nautilus to implode, thereby killing the animal,” the agency noted. It is not an open water species, and is found instead near reef slopes and along the ocean bottom, usually at depths between 100-500 meters. These constraints, exacerbated by warming ocean waters, also contribute to the isolation of populations.

Certain illegal reef fishing practices also affect the nautilus’ habitat. In the Philippines, Indonesia and Malaysia, prime nautilus territory, reefs are blasted with explosives and poisoned with cyanide. Though these practices are aimed at harvesting reef species in shallow water, the nautiluses are indirectly affected due to changes in the coral reef community structure, loss of fish biomass, and a decrease in food, the agency said.

Since the agency’s 90-day finding on the CBD’s petition, new information regarding the effect of ocean acidification on shell formation have lead the agency to conclude that the effects of acidification are highly variable among shell-producing species, and since there are no available studies specific to the chambered nautilus regarding ocean acidification, the agency has downplayed this as a significant threat. Other threats may include pollution from underwater mining, predation from sharks, triggerfish and octopuses, lack of regulations and enforcement, and climate change.

The agency considers the shell trade to be the primary threat to the nautiluses. In recent years, the harvest of large shells has noticeably declined, more shells from younger specimens are being sold, and the source of the shells has continuously shifted due to depletions. Of the 20 nations where nautiluses are known to occur, about half have targeted historic or current fisheries, comprising three-quarters of the known range, and most with uncertain regulation, the agency said. Of even higher concern is the illegal trade.

Chambered nautiluses are being proposed for threatened status under the ESA. The difference between endangered status and threatened status is a matter of time, with endangered status being granted to species that are in danger of imminent extinction, and threatened status being granted to species that are in danger of extinction within the foreseeable future. The term “foreseeable future” is defined by the listing agencies (NMFS for marine species and U.S. Fish and Wildlife Service for land-based species) on a species by species basis. In the case of the nautilus, the NMFS has set that time frame at 40 years, due to many factors, including the species’ own generational longevity.

The agency finds that critical habitat is not determinable at this time, but may publish a habitat determination for U.S. waters, such as American Samoa, in the future only if further information makes that determination feasible.

Comments are requested within 60 days of the publication of the listing proposal, currently scheduled for Oct. 23.

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