– While it hasn’t become Cape Cod just yet, the number of whale sightings around New Jersey has increased substantially this year, suggesting that the state’s coastal waters are now clean enough to sustain humpbacks, finbacks and other species during the feeding season.

Since April, dozens of whales have been spotted from Sandy Hook to Cape May chasing down schools of small fish sometimes within a mile of New Jersey’s shoreline.

“They seem to be staying in the same area all season long, which is something we haven’t really seen before,” said Amy Bergeron, a marine biologist with the Cape May Whale Watch and Research Center, which runs tours along New Jersey’s southern coast. “Some are not even a mile out. We know they come here for the food, and you’re seeing huge batches of bait fish close to the shore.”

As of last week, the Cape May center had 37 whale sightings, compared with 15 through October last year. And Gotham Whale Watch, a group of “citizen scientists” who catalog marine mammals in New York and farther south, has reported 57 whale ­sightings so far, up from 43 in 2013.

The news has drawn thousands onto whale-watching boats hoping to see the majestic mammals gliding through the ocean and perhaps even glimpse a humpback leaping out of the water. It has also prompted authorities to issue alerts to boaters fearing whales are coming too close to shore.

Academics are treating the reports cautiously, since most of the sightings come from groups associated with local whale-watching boats. But some environmental officials and marine biologists say the reports should be taken ­seriously.

“It’s tough to definitively say there are more whales in an area without more baseline information,” said Jackie Toth Sullivan, a marine mammal scientist and adjunct professor at Richard Stockton College. “That being said, an increase certainly seems plausible given the amount of anecdotal reports coming in from boaters, whale-watching boats and beachgoers alike this season.”

Annual migration

Beginning in April, thousands of humpback whales usually pass New Jersey dozens of miles off the coast during their annual migration up the East Coast from their winter mating and birthing grounds in the West Indies. Many congregate around Cape Cod to feed on the abundant sea life near a large underwater plateau in Massachusetts Bay or head farther into the North Atlantic for food.

Cleaner waters affect the bottom of the food chain, allowing plankton to flourish closer to shore. That in turn provides a food source for small bait fish like menhaden. And whales like nothing more than to scoop a school of menhaden into their mouths for lunch.

Even though an estimated 23 billion gallons of raw sewage spills from hundreds of outfall pipes into New Jersey’s rivers and bays each year, the state’s coastal waters are considered the cleanest they have been in decades.

“Clean water means more fish and so you have a new feeding ground,” said Paul Sieswerda, founder of Gotham Whale. “You still have all these sewer pipes heading into the water, so it’s not perfect but it’s much improved. I remember the Styrofoam, the beer cans, the stuff that used to be so prevalent, and that’s no longer the case.”

Whales coming closer to shore also means the possibility of more boaters hitting them. After three strikes along the Eastern Seaboard last spring, the National Oceanic and Atmospheric Administration and New York environmental officials issued alerts to boaters to slow down and watch out for whales.