I was looking for info on the life cycle of jacks and couldn't find much. The best I got was an e-mail reply from WDFW. I wish I would have saved it, anyway it was on the lines of jacks are males returning and maturing 1-3 years before the others of the same year class and they think the reason is so there will always be some males to fertalize the eggs in case there was a disaster with the normally returning year class. Chinook have the most jacks, coho have fewer and other salmon species have few to none. The jacks die after attemting to spawn, the normal year class larger males will run them off the redds.
The way I read the regs for that area is the only jacks you can keep would be coho .