Norwich has bypassed Groton as the biggest city in southeastern Connecticut, and Hispanics have replaced blacks as the largest minority group in the region, according to U.S. Census numbers released Thursday.

Norwich grew at a brisk 12.1 percent pace during the past decade, thanks to its proximity to the Mohegan Sun and Foxwoods Resort casinos, taking its place as the most populous city in the region, with 40,493 residents. Many of New London County's northern towns followed suit, with Lyme, Bozrah, Griswold and Colchester growing by double digits in the past decade.

"This reflects defense downsizing and the casino population moving north," said John Markowicz, executive director of the SouthEastern Connecticut Enterprise Region, a business development group. "Population will migrate to where the jobs are."

Groton, which grew only a half-percent between 2000 and 2010, came in as the second-largest municipality in the region, with a population of 40,115. Groton Town Manager Mark Oefinger could not be reached to comment, but Norwich Mayor Peter Nystrom saw the Rose City's relatively strong growth as tied to a more extensive housing stock and lower rental rates than in Groton.

The region's other city, New London, also showed a positive trend, growing 7.6 percent during the decade. Its population now numbers 27,620, new Census figures show.

"I think that bodes well for our region when two of its three urban communities experience that much growth," said James S. Butler, executive director of the Southeastern Connecticut Council of Governments.

Much of New London County's population growth has been spurred by the influx of minorities, according to the latest Census figures, with Asians and Hispanics recording the most noteworthy increases. Those identifying themselves as white fell from 87 percent a decade ago to 82.2 percent today.

Hispanics, who accounted for 5.1 percent of New London County's population a decade ago, have grown to 8.5 percent of the total. African-Americans' slice of the population pie increased from 5.3 percent to 5.8 percent but didn't keep up with the rising tide of Hispanics.

And Asians may be catching up with both minority groups. The Asian population that a decade ago accounted for 2 percent of the Census totals in New London County now makes up 4.2 percent.

"After 9/11, there was a lot of outmigration from New York City," Markowicz said.

In Norwich, for instance, Asians constitute 7.7 percent of the population; a decade ago, they accounted for 2.1 percent of the city's total. While the Asian population nearly quadrupled in Norwich, Hispanics more than doubled their relative presence, from 6.1 percent to 12.6 percent, and the black population made a major move as well, from 6.8 percent to 10.4 percent of the total.

"We are the bedroom community for our two neighboring casinos," Nystrom said.

Asians registered a significant increase in New London, but Hispanics in the city made even greater strides, going from 19.7 percent of the population a decade ago to 28.3 percent in the most recent Census. Blacks actually lost ground to other groups, going from 18.6 percent of the New London population in the previous Census to 15.3 percent in the most recent figures.

Lyme population jumps

Among the region's towns, only Lebanon and Old Saybrook lost population, according to U.S. Census figures. New London County's overall growth of 5.8 percent surpassed that of the state, which registered a 4.9 percent increase.

The wealthy enclave of Lyme emerged as the fastest-growing town in New London County between 2000 and 2010, according to the Census, with a 19.3 percent increase in population. The Census found about 400 more people in Lyme last year than had lived there 10 years before.

"If they're here, I don't know where they are," said Lyme First Selectman Ralph Eno, who disputed the Census findings. "If you counted horses and dogs, maybe that would account for it."

Rural Lebanon was the only town to lose significant population, declining by about 1,600 residents, or 18 percent. The shoreline town of Old Saybrook, which is in Middlesex County, lost 1.2 percent of its population over the past decade.

l.howard@theday.com