NEW SHARON – Hand-fed brook trout raised in Maine’s hatcheries have become too domesticated by wild standards, prompting efforts by biologists to develop a hardier, more resilient stock.

The ability of the hatchery fish to survive and reproduce healthy offspring has been weakened further because too few brood fish were used to produce eggs, narrowing the gene pool.

“We were looking for a way to replace the domesticated short-lived trout,” said Forrest Bonney, a biologist with the Department of Inland Fisheries and Wildlife.

To address that problem, biologists have turned to Maine’s natural wild stock.

To obtain naturally hardy genetic material, they took brown trout eggs from fish at river outlets with no previous record of ever having been stocked before.

Beginning in 1995, eggs were stripped from the trout of Sourdnahunk Lake in Piscataquis County and in 1996 they were taken from the Kennebago River in Franklin County.

A hundred female and 100 male brook trout from each of the two locations, over a three-year period, established two new hatchery strains. Their offspring were released into eight lakes in Franklin, Oxford, Kennebec, Cumberland and Washington counties.

Both the Kennebago and the Sourdnahunk were released in equal numbers together and for the past four years have been studied, using comparisons between the two and the so-called domesticated strains.

In McIntire Pond in New Sharon and other lakes, Bonney has been testing the new breeds of brook trout. Upon release, their fins were clipped to identify their strains and age.

Overall, Bonney said, the two strains of wild trout have lived to 2 and 3 years so far. That’s much closer to the wild trout’s natural age of 4, compared with domesticated stock that usually survive up to a year.

But he noted that the wild ones grow at a much slower rate during their first year. And he said there is some concern that anglers, used to yanking out the more abundant, faster-growing young ones, may be less than enthusiastic over the wild ones at first.

After four years of comparative study between the Kennebago and Sourdnahunk strains, the indications are that the Kennebago is the hardier of the two.

Bonney will return a few more times this fall to McIntire Pond to complete his study here before turning his attention to the more than 200 other lakes in his region.