A total of 100 stingrays was recorded at the North Sound sandbar at the latest population count last week.
At the last count in July 2016, there were 107 rays at the site.
The figures are encouraging, said Guy Harvey, the artist and environmentalist who organizes the biannual stingray census through his ocean foundation.
Both counts show stingray numbers in three figures for the first time since 2008. Mr. Harvey believes the January count would have been as high as in July, but a combination of factors, including bad weather and the absence of some key, experienced volunteers, meant a few rays were missed.
The researchers count the rays by lifting them on to the boat, maneuvering them into a paddling pool set up on deck, taking measurements and checking tag numbers or fitting tags for new rays.
In the January census, 82 females and 18 males were counted. There were 10 new rays not previously recorded at the site, and 90 recaptured.
“We are really encouraged by the numbers,” Mr. Harvey said, “which have gone from the mid-70s to the high 90s and now into the hundreds over the past few years.
“The fact that we encountered 10 new rays that we hadn’t seen before shows how dynamic this system is. We have resident rays that have been there since the beginning. There are others that come and go.”
One of the rays had serious wounds, possibly from a boat propeller, when the crew visited the sandbar in December, but the wounds appeared to have completely healed when checked during the January census. Boat strikes remain a concern, and Mr. Harvey warns that a number of ongoing management issues at the sandbar have yet to be addressed.
He estimates that three or four rays are killed each year by boat propellers, particularly by boats maneuvering carelessly on days when the weather is rough.
Other issues including overcrowded tourist boats and concerns that some guides continue to lift rays out of the water for photo opportunities, despite warnings that it endangers the animals.
Mr. Harvey said those issues have persisted for a number of years and repeated calls have been made for the Department of Environment, the Port Authority and others to come together to put a management plan in place for the attraction.