Hatchery fish

Jacking is probably the most obvious example of epigenetics. Changes in epigenetics have been seen in Columbia river chinook hatcheries for some time. Some years see very large proportion of jacks (3 year old fish) making up some runs, and more recently mini-Jacks (2 year old fish) making up significant numbers of fish in some hatcheries, mini-Jacks are uncommon in wild runs. The mini-jacks were correlated with higher body weight and size of smolts.
 
Some people say all the hatcheries did was mask the huge decline in 1970 with our wild stocks.

Lots of mini jacks in the Chilliwack system, 2 pound chinooks. A 3 year old chinook is quite big and pretty hard to tell from a 4 year old.

As for another small system i fish in the lower main for Coho the avg hatchery chinook is like 4-5 pounds and it seems like the wilds are always much bigger 5-8 pounds.
 
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