A proposed rule banning steel wire leaders in Hawaii’s longline fishery to protect accidentally caught sharks is nearing implementation.

The National Marine Fisheries Service proposed the rule after the Western Pacific Regional Fishery Management Council voted last June to ban the use of wire leaders, which are used at the terminal ends of fishing lines near hooks. A final and enforceable rule could become effective within a few months.

Most of the 160 or so affected vessels in the Hawaii Longline Association’s fleet have already stopped using wire leaders and have switched to monofilament nylon after the association announced it would voluntarily make the switch in 2020.

Replacing wire leaders with monofilament leaders would more easily allow accidentally hooked animals, in particular oceanic whitetip sharks, to bite off hooks they are caught on before fishing crews pull them and fishing gear on board.

The use of monofilament leaders would also reduce the amount of so-called trailing gear still attached to sharks once they escape or are freed, which has been shown to increase their long-term survival rate.

Wire leaders, which can be stronger than the main fishing line and protect against breaking, used to be the preferred material because they protected against “fly backs,” when fishing lines under tension break and whip back toward fishing vessels.

“Although they reduce fly backs, wire leaders reduce the chances that sharks may bite off the line and release themselves before the crew retrieve the gear,” the NMFS said in its proposal. “We expect sharks that release themselves before the gear is retrieved to have reduced mortality relative to sharks that are released after being brought to the vessel.”

Eric Kingma, executive director for HLA, said that fly backs are real concerns with monofilament leaders, but different techniques and tools are being tested to ensure the safety of fishing crews.

The switch to monofilament leaders is expected to reduce oceanic whitetip catch and mortality by about 30%.

Oceanic whitetip sharks were listed as threatened under the Endangered Species Act in 2018. The primary threat to the species, which has experienced an 85%-90% drop in its Pacific Ocean population since the 1990s, is accidental bycatch, according to the National Oceanic and Atmospheric Administration.

The proposed rule would also require longline fishers in Hawaii and American Samoa to remove trailing gear from caught oceanic whitetip sharks and release them.

The NMFS took public comment for the proposed rule and said nearly all the comments have been in favor of the proposal.