Environmentalists and some Hawaii officials fear a federal agency’s proposed rule could roll back state laws that discourage the killing of sharks in the Pacific.

In most shark killings the creatures are hunted for their fins, a part that yields gelatinous cartilage for a soup delicacy that in Asian countries can command as much as $100 a bowl.

Environmentalists have likened the practice of lopping off sharks’ fins and tossing their carcasses back into the sea to the slaughter of African elephants for their ivory tusks.

Critics say the National Oceanic and Atmospheric Administration’s proposed rule would pre-empt stricter laws in Hawaii and nine other states and U.S. territories that ban the possession, distribution or sale of shark fins.

"The rule is unnecessary," state Land Board chairman William Aila said in an interview. "In our mind, there’s no reason for the federal pre-emption."

Authorized vessels currently are allowed to take fins off sharks in federal waters, but the fins may not exceed 5 percent of the total shark catch weight — details that can make enforcement difficult, officials acknowledge.

Under NOAA’s proposed rules mandated by Congress under the Shark Conservation Act of 2010, fishing vessels would be prohibited from removing the fins in federal waters and must unload their catches of sharks with fins intact at docks under U.S. jurisdiction.

The agency’s regional administrator, Michael Tosatto, said the proposed rule was designed to curb shark finning and its wasteful practice of discarding the carcass in the ocean.

Tosatto acknowledged his agency’s proposed rule could pre-empt states’ laws depending on the interpretation of the states’ shark-finning laws. He said his agency was in talks with various states, including Hawaii, trying to figure out a way to avoid pre-emption.

The deadline to comment on the proposed rules is July 8.

The Pew Charitable Trusts, a public-policy group, said it has launched a petition drive asking NOAA to prevent pre-emption in states and territories with shark fin bans, including Hawaii, California, Washington, Oregon, Illinois, Delaware, Maryland, Guam, American Samoa and the Commonwealth of the Northern Mariana Islands.

"Rolling back those fin trade bans would be a considerable setback," said Jill Hepp, Pew Trusts’ director of shark conservation.

"Those bans have had a positive impact. … It closed off these markets for fins in the world."

Hepp said trade in shark fins occurs worldwide and that Hong Kong is the largest shark fin market, representing about 50 percent of the global trade.

The Pew Trusts said 83 countries exported more than 22.7 million pounds of shark fin products to Hong Kong in 2011.

Researchers have estimated about 26 million to 70 million sharks per year are caught globally, according to the Western Pacific Regional Fishery Management Council.

Pew Trusts officials said the loss of sharks could cause irreversible damage to the ocean because as apex predators, sharks play an important role in maintaining a balance in the marine environment.

Of the 480 species of sharks around the world, information is insufficient to determine the status of 209 species but about 150 are at risk of extinction, Pew said.

No sharks are on the U.S. endangered species list, but several are being considered, including the dusky shark or Carcharhinus obscurus; great hammerhead shark or Sphyrna mokarran; great white shark or Carcharodon carcharias in the northeastern Pacific Ocean; sand tiger shark or Carcharias taurus; and scalloped hammerhead shark or Sphyrna lewini.

Paul Dalzell, senior scientist for the Western Pacific Regional Fishery Management Council, said it is quite likely overfishing of sharks for their fins is occurring. He said a couple of species of sharks, such as the silky shark and oceanic whitetip, seem to be declining in the Pacific.

Dalzell said sharks have been a bycatch, or unintended catch, of longliners based in Hawaii who are fishing for bigeye tuna and swordfish, and that shark catches represent less than 1 percent of the total fishing catch.

Hepp said what some people are missing is the lack of management that exists outside the U.S. jurisdiction, and the role of Hawaii and other states that have banned shark fins in reducing the market for them.

She said she’d like to see the proposed rule move forward without pre-empting state bans on shark finning.

State Sen. Clayton Hee, who pushed through the ban on shark finning in Hawaii, said he feels pre-emption would allow Hawaii and other coastal states to be a staging area for shark-finning vessels and overfishing.

"You don’t need to be a scientist to know the ocean is running out of fish," he said.

"If you go to Tamashiro Market, you see fish imports from New Zealand, because Hawaii cannot support itself by fishing."