Ships operated by the world’s largest cruise companies were the scene of 237 alleged serious crimes in the past two and a half years, according to data obtained by the Miami Herald.

Those statistics, which will be posted on the websites of the participating cruise lines starting Thursday, are a much higher number than the public has previously seen. Because the U.S. Coast Guard publishes information only about crimes closed by the FBI, the incidents between 2011 and the first half of this year revealed in government reports totaled 44.

But the cruise companies — Royal Caribbean Cruises, Carnival Corp. and Norwegian Cruise Line — decided to voluntarily release the information for their eight North American brands, announcing the plan during a U.S. Senate Committee on Commerce, Science & Transportation hearing focused on the cruise industry last week.

The day before the hearing, committee chairman Jay Rockefeller, D-W. Va., had introduced a bill that would require the information be made available to the public.

“With the growing criticism about how effectively the government website is communicating our onboard rates, it just made good sense to try and take the argument out of the realm of ‘Gee, we wish we knew’ and really share very openly what the incident rates are,” said Gary Bald, a senior vice president at Royal Caribbean Cruises who oversees safety and security.

He added: “I’ve been a little bit frustrated with the message that seems to get play out there that we have such an out-of-control problem on our ships — and it’s really not true.”

The lines are posting the total number of alleged incidents — reported by passengers or crew — in each of the categories that are specified in the 2010 Cruise Vessel Security and Safety Act. Those include sexual assault, theft greater than $10,000, tampering with the vessel, assault with serious injuries, kidnapping, missing U.S. nationals, suspicious death or homicide. The cruise lines are reporting rapes and other sexual assaults in two separate categories, though the government uses only a single category.

Kendall Carver, chairman of the International Cruise Victims Association, said the voluntary reporting “may be a big step or a small step forward.”

“We would hope that it’s a complete report, but I think the government still needs to pass the laws so that cruise lines are forced to do it,” said Carver, who has been pushing for greater transparency about cruise ship crime for years.

He said he also wants cruise lines to publicly release reports of all alleged crimes, not just the categories laid out in the CVSSA.

The annual totals of the most serious crimes — 99 in 2011, 88 in 2012 and 50 so far this year — are relatively small, given the nearly 17 million passengers North American cruise lines carry. Allegations of rape were the most common, with 70 total cases reported. There were 58 alleged reports of other sexual assaults, 50 thefts and 39 assaults with serious injury.

Royal Caribbean International, Celebrity Cruises, Azamara Club Cruises and Norwegian Cruise Line will each release individual data going back to late 2010. For the same time period, Carnival Corp. is posting combined totals for its four North America-based brands, which carry more than seven million passengers a year: Carnival Cruise Lines, Princess Cruises, Holland America Line, and Seabourn Cruise Line. Carnival released a draft version of its numbers on Wednesday to the Miami Herald.

Tom Dow, who heads up government affairs for Carnival Corp., said the company is following its practice of consolidating financial results rather than releasing information for individual lines.

“We think that it will provide a clear picture which reinforces what we think most people already understand,” he said. “As it turns out, a great number of these allegations are either not taken up for investigation or are otherwise resolved.”

Michael McGarry, senior vice president of public affairs for the Cruise Lines International Association, said the trade group will also post the statistics and expects other member lines in North America “will voluntarily add to CLIA’s aggregation soon.”

Adequate information was not available to calculate the crime rate per 100,000 passengers for cruise ships — which is how the FBI tracks crime statistics under the Uniform Crime Reporting protocol on land — with the new data from the cruise lines.

But a report by James Alan Fox, a Northeastern University criminologist who crunched data for the Cruise Lines International Association, looked at rates from 2010-2012 for 15 cruise lines owned by the three major cruise companies. The report, which representatives from Carnival and CLIA both referenced in interviews Wednesday, says the rate of rape per 100,000 people was 5.9, while the rate of other sexual assaults was 8.7 and the rate of assaults with serious injury per 100,000 people was 3.8.

In the U.S. for that time period, he wrote, the crime rate for forcible rape was 27.1 per 100,000; other sex offense was 97.2 and aggravated assault was 248.9.

Fox said in an interview Wednesday that several factors contribute to a safer environment aboard cruise ships, including older and well-heeled demographics; the inability of offenders to escape at sea; screening for crew and passengers and the presence of surveillance cameras on board.

“So despite the fact that you have lots of people with free time and access to alcohol and sometimes in crowded spaces, these other factors of self-selection and screening as well as security measures go a long way toward making sure that cruising is safe,” he said.

Ross Klein, a professor at Memorial University of Newfoundland who studies the cruise industry, called Fox’s report “smoke and mirrors” because it did not highlight rates of crime on specific cruise lines, did not specify which lines were included and failed to define rape or sexual assault.

While Klein said he believes the release of data by the cruise lines is an “important move,” he said additional transparency will be key.

“The question becomes whether the numbers they put out, whether they’re going to be open to having them audited by anybody and how reliable they are,” he said.

In a statement Wednesday, Rockefeller pledged to keep up the pressure on cruise lines.

“Details matter and that’s what I’ll be examining when cruise lines start posting their internal crime data. While I’m skeptical about self-regulation that’s only the result of serious public scrutiny, it’s possible some cruise lines have gotten the message that we expect a level of transparency from the industry that’s been sorely lacking,” he said.

“But if we’re really going to make a difference for consumers, I believe it’s going to take legislative action to make sure this industry is required to give consumers the information they need and deserve when they’re making a decision about taking a cruise.”

Carolyn Spencer Brown, editor in chief of the website CruiseCritic.com, said some members of the site have said they’re happy to have more information, while others seem unaware that crime is an issue at all. She said she believes greater transparency is a positive.

“Information is power — as a consumer, I like to be able to do my research,” she said. “As a cruise traveler and somebody who’s covered the industry for 15 years, I can’t imagine being afraid or nervous. But the more information out there, I think the healthier we all are.”

The Florida Center for Investigative Reporting contributed to this story.