Independent monitors hired by the National Oceanic and Atmospheric Administration to track catch limits and document endangered species interactions on U.S. fishing vessels are finding themselves in increasingly dangerous waters.

On Thursday, two nonprofits seeking to bolster protections for fisheries observers released statistics showing that the number of reported incidents of intimidation, harassment and assault on these workers more than doubled from 35 in 2013 to 84 in 2015.

The Association for Professional Observers and Public Employees for Environmental Responsibility also said that NOAA officials have done little to respond to the uptick in harassment.

In 2015, NOAA data showed that no enforcement action was taken despite a record number of assaults, and that more than half the cases remained open even though many months had passed since the incidents had been reported.

“For Fisheries Observer, NOAA means ‘No Assistance Available’ because they can expect no support if they are attacked or prevented from doing their jobs,” PEER Executive Director Jeff Ruch said in a press release. “NOAA views the fleets as its constituents and these independent monitors as necessary inconveniences.”

About 700 observers monitor fleets in 47 fisheries in U.S. waters, with about 60 of them assigned to NOAA’s Pacific Islands Regional Office to oversee longline tuna and swordfish vessels in Hawaii and American Samoa.

Their job is to document how many fish come aboard a vessel, and note any instance in which a protected species, such as a seal, sea turtle or dolphin, is killed. This data is then used to help agencies, such as NOAA and the Western Pacific Regional Fishery Management Council, manage fish populations.

Observers are also on board to make sure fishermen follow all the rules, such as checking what type of bait is used and making sure that hazardous waste doesn’t spill into the ocean. While observers are not law enforcement officials, what they see and what they report can lead to hefty fines and lower profits for fishermen.

As a result, observers are often looked at as tattle-tales by the very fishermen they’re asked to share cramped quarters with on the high seas for days, weeks and even months at a time. This can lead to tension between observers, captains and their crew.

Last year, the mysterious disappearance of American fisheries observer Keith Davis made national headlines when a Chinese vessel he was on reported him missing in international waters 500 miles off the coast of Peru. Many of his relatives and friends suspected he was the victim of foul play.

Davis, who had ties to Hawaii, worked as an observer for MRAG Americas and was well-known for his adherence to safety protocols. He was also a member of the Association for Professional Observers, where he helped develop an international bill of rights to protect observers.

The association now advocates for more safety measures for those in the profession, including outfitting observers with panic buttons and their own satellite phones so that they can contact officials should they get into trouble.

The association and PEER have long pushed for more accountability and oversight of the observer program to cut down on harassment, assaults and retaliation. But the nonprofits have criticized NOAA’s response, saying that any attempts at reform have been “half-baked.”

Elizabeth Mitchell, president of the Association for Professional Observers, was critical of a recent NOAA initiative to replace human monitors on fishing vessels with cameras and other technology.

“Three observers have been murdered in recent years, including my colleague, Keith Davis,” Mitchell said in Thursday’s press release. “Rather than enforcing observer protections, NOAA has joined with the fishing industry in a push to replace observers with cameras despite the absence of any reliability or accountability controls.”

UPDATE

NOAA responded Friday to the concerns raised by PEER and the Association for Professional Observers in a statement highlighting that the safety of at-sea monitors is a priority for the agency, and that any concerns should be addressed directly to the NOAA Office of Law Enforcement for investigation.

“We take seriously every report of violence, threats, or harassment against professional observers and we evaluate all complaints received.” said James Landon, who is director of the NOAA Office of Law Enforcement.

NOAA added that its ability to complete investigations in a timely manner is contingent on the evidence provided by observers and other witnesses.