Each generation removed begins to take on more physical and biological characteristics of the parent strain.
"The backcrossing problem is a big reason why it is hard to distinguish splake from brook trout. Second- and third-generation backcrossed splake can look nearly exactly like brook trout (or lake trout). We don't know which ponds splake will be able to reproduce in successfully, so we have to assume that they can reproduce in every pond," Preall said.
Therefore, any pond in which splake are identified is immediately ineligible for the state brook trout record, he noted.
The only true way to determine if a splake has infiltrated the gene pool is to open the fish and count the worm-like appendages - known as pyloric caecae - that hang from the fish's intestine.
Most native brook trout will have 25-35 pyloric caecae. Get more than 55 and the state will not recognize the fish as a brook trout - more than 65, and the fish is considered a splake. Lakers have around 95.
The count on my fish came in at around 65. Another fish I carried out the same day that was 4 pounds, 10 ounces had 61 pyloric caecae - making it also ineligible for a brook trout certification.
The system, however, is a bit subjective - especially if fish are actually third-, or fourth-generation "backcrosses."
Preall said an angler would have a legitimate argument a fish with a 55-65 pyloric caecae count is indeed a brook trout. And, it has been noted as the generations become removed, the pyloric caecae count does decrease, making the strain closer to a certifiable brook trout.
So, at some point, a "backcross" could in theory be certified a record, provided a splake had not been identified in the pond it came from and its pyloric caecae count falls below the 55 standard set by the state.