PROVINCETOWN — With the count of North Atlantic right whale sightings in Cape Cod Bay down to zero Thursday, the end-of-season findings by the Center for Coastal Studies indicate what could be new realities: More animals are showing up each year, and the length of time they’re staying in the bay is longer.

“There are two trajectories,” said Charles “Stormy” Mayo, the center’s right whale ecology program director. “Our trajectory is going up while the total number of right whales is going down, fairly steeply.”

The center has studied the right whales in the bay for several decades, currently with airplane surveys for population counts and boat surveys to identify food densities in the water. The data collected is used, in part, to help the state Division of Marine Fisheries place and lift restrictions in the bay on trap gear fishing and vessel speeds.

The right whales — now considered at risk of extinction in the coming decades along the Atlantic coast due to deaths and injuries from being caught in fishing rope and hit by ships — have a current population of around 411. They typically arrive to feed in Cape Cod Bay in late winter and leave by the end of April, along an annual migratory path that stretches from Florida to Canada.

So far, the center has confirmed 267 individual right whales seen by either plane or boat for the current season, making that roughly 65 percent of the estimated total population. Considering the complete range of the whales' migration along the East Coast, the concentration in the relatively small area known as Cape Cod Bay is "remarkable," Mayo said.

The count of 267, too, is likely an underestimate given that bad weather kept the plane on the ground for two weeks this year, he said.

The other change implicit in the center's report is that the whales are arriving earlier than before and staying longer, Mayo said.

“This year we had bona fide sightings in early December, and some observations suggested they were here in November,” he said.

The length of time the right whales are in Cape Cod Bay affects both the speed that commercial vessels can travel and when commercial lobstermen can set their traps and fish. This year, when vessel speed limits would have been lifted as of May 1 in the bay along with bans on lobster traps, the ongoing presence of right whales led state officials to extend restrictions more than a week into May. That extension beyond May 1 led South Shore commercial lobstermen to hold a rally the morning of May 9 at the Plymouth town dock, but then the state lifted the ban later that day after the Center for Coastal Studies reported one whale sighted in the bay.

"The food collapsed pretty much about a week ago," Mayo said of the boat survey results.

Since then the weather hasn’t been the most accommodating, "but it seems as though most of the guys have been getting gear out,” said David Casoni, a commercial lobsterman based in Sandwich, on Sunday.

At the rally in Plymouth, with the annual trap gear ban from February through April in Cape Cod Bay, the lobstermen said it felt as though they were already way behind their competitors, such as lobstermen north of Marshfield, who had been able to lobster without restrictions.

About 200 commercial lobstermen are affected by the annual ban in Cape Cod.

“I’m not sure they’re arriving earlier,” Casoni said of the right whales. More predictably, the lobstermen say they might see the right whales at the end of March and in April, and a week or two, in the past few years, he said.

“They still aren’t here in January, and I don’t know if they find any in February,” Casoni said.

Typically, the lobstermen need a month to put their traps in the water in the early part of the year, and they then fish through November or so, and then take another month to bring their traps back out of the water.

The peak day for right whale sightings was April 7, with 129 individual whales seen on one aerial flight, according to the center's data.

Scientists and right whale conservationists want to both prevent deaths and boost births in efforts to stop a population decline that has been traced back to 2010, given a new statistical model unveiled in 2017. With the recorded deaths of 17 animals in U.S. and Canadian waters, and no recorded births in the following birthing season, and then another three recorded deaths in 2018, the National Oceanic and Atmospheric Administration announced an unusual mortality event, or UME, for the North Atlantic right whale, which releases more money for study and research. So far there have been no recorded deaths of right whales this year, according to federal sources.

Part of the center’s research this season was surveying areas adjacent to Cape Cod Bay to determine if right whales are congregating for extended periods of time prior to entering the bay, but Mayo said that so far that has not proven correct. That type of data can help marine mammal conservationists and federal regulators determine how much time the animals may be exposed to risks such as ship strikes and rope entanglement, Mayo said.

“This tells us that the offshore areas are transit areas,” he said.

— Follow Mary Ann Bragg on Twitter: @maryannbraggCCT.