Notifying speeding sailors that regulations are in place to protect North Atlantic right whales has been effective in protecting the endangered whales from ship collisions, a new study has found.

In late 2008, the National Oceanic and Atmospheric Association instituted a ship strike reduction rule that requires vessels 65 feet or longer to lower their speeds to 10 knots or less in certain areas that are seasonally occupied by the North Atlantic right whale.

These areas include an area to the southwest of Martha’s Vineyard and Cape Cod Bay and waters east of Cape Cod. The rule is in effect for varying time periods depending on the area; the northeast zones are in effect roughly from Jan. 1 to July 31.

Right whales migrate seasonally from their breeding grounds off the coast of Florida, Georgia and South Carolina to plankton-rich ocean feeding grounds in New England and Canada.

The speed reduction rule was set to expire in December 2013, but the regulations were instead made permanent.

According to a study NOAA released last week, notifying mariners and issuing citations have been effective tools in assuring compliance with the regulation. NOAA scientists also report that they have not seen one right whale that has been struck by a large vessel in regulated areas since the regulation went into effect.

The study, led by NOAA, looked at how 8,009 vessels that made more than 200,000 trips between November 2008 and August 2013 complied with regulations. The study looked mostly at areas where North Atlantic right whales are known to travel.

Almost all the ships were notified of the speed restrictions, a NOAA press release said. A total of 26 owners or operators received citations and were fined.

The study found that compliance was low when the regulatory period began but improved over time, and those that received fines or citations improved their compliance. NOAA used informational letters, public summaries of vessel operations and direct at-sea radio contact to ensure compliance, the press release said. Cargo vessels had the most improved compliance rate.

“We’ve shown that notifying the mariners of their responsibilities, along with issuing citations when applicable, results in widespread compliance,” NOAA Fisheries Office of Protected Resources director Donna Wieting said in the press release.

NOAA said North Atlantic right whales are very vulnerable to ship collisions; the two biggest threats the mammals face are ship strikes and entanglement in fishing gear.

Right whales are also critically endangered. Scientists estimate that there are 450 of the whales alive today.