Rockfish are thriving in the Chesapeake Bay, a Maryland state agency reported yesterday, an encouraging sign for the ecosystem's health amid reports of its decline.

Biologists from the Maryland Department of Natural Resources counted 2,348 newly spawned rockfish in samples taken at 22 sites around the bay this summer. An average of 17.8 fish were caught in each sweep of a 100-foot seine net, six more than the average during the five decades the state has measured the population.

It's encouraging news, especially given recent reports that portions of the bay might be dying. The Chesapeake Bay Program reported this month that 5 percent of the bay was anoxic this summer, so depleted of oxygen that it was lethal to almost all fish. That was the highest level reported in 20 years of record-keeping. Despite evidence of the expanding "dead zone," anecdotal reports from fishermen suggest that rockfish are abundant.

"It's probably been the best fishing in two or three years," said Paul Puher, a naval engineer who fishes the South River with his sons near his home in Davidsonville. "We just had fish and some great white wine the other day."

Don Cosden, a regional coordinator in the fisheries unit of the state agency, said the success of the rockfish is "one indicator that the bay is not dead, certainly." He said it is a sign that the low oxygen level in portions of the bay "probably affects some species more than others." Cosden cited a successful curb on commercial and recreational fishing as one reason for the increased population.

Maryland biologists have monitored the spawning success of rockfish and other species in portions of the bay annually since 1954. The index covers four major spawning systems: the Choptank, Potomac and Nanticoke rivers and the Upper Bay. Scientists visit each site monthly from July to September, the period after the spring spawning season, collecting fish in nets. The most rockfish collected in a net was 50.8, in 2001. The fewest was 1.2, in 1981, according to state data.

The fish population tends to vary widely in the four spawning areas. This year, scientists found many fish in the Upper Bay and in the Potomac River and comparatively few in the Nanticoke.

The survey also documents spawning success in several other fish species. The American shad population, for example, was high for a sixth consecutive year. White perch reproduction was average.