Lake WA Trib Salmon smolt/jack in Dec.?

[fisherben]

Hello forumers! This might be somewhat of a late issue, however this certain fish has been on my mind for months and I have never been exactly sure of what it was. Consequently, I have decided to find out once and for all! Back in mid-December (Dec.16 to be exact) my friend and I decided to go on a short catch-and-release fishing trip to one of the small northwestern tributaries of Lake Washington. We fished only a few hundred feet upstream of the mouth, using small spinners and were really surprised to catch something other than a cutthroat at the first pool. When the fish hit it immediately jumped clean out of the water and did a little tail walk after that. Once the fish was in the net we knew it was not the usual coastal cutthroat. Nothing about the fish's short fight was alike to a cutthroat. The majority of its fight was aerials and not much of any runs. It was about 10 inches long and very bright and silvery (much brighter than a cutthroat), with small, circular spots. The fish was in fact so bright that at first we believed it to be a kokanee, however we quickly decided that it could not be. Don't worry, the fish was safely released! For a little while I contemplated whether it was a chinook or coho, and all signs indicate the latter. It has a white gum line, small, circular spots (not large and irregular like a chinook), and the shallow-forked tail of a coho. Of course my identification can never be 100%, but I think I'm pretty spot on. The main question I have is HOW old is this fish, and WHY was it in fresh, moving water at this time of the year? I understand that many adult coho remain in the rivers here well into January, however there is NO WAY this could be a fully grown fish! It's only 10 inches! I'm stuck in between either an extremely small jack coho that came into the system very late, or a very large coho smolt that would be leaving the system in the spring of 2013. You would expect that by this size, this fish would be out in the salt water! Out of curiosity this has been bothering me for quite some time, and I would really appreciate an answer! For future reference, what is the time range of the coho run in Lake Washington?, and how big and old are the coho smolts when they usually leave the system for the ocean? What is the min/max size for a jack?
Thank you guys so much! You're awesome!

[G-Man]

Contrary to what you may think, young coho spend at least a year in fresh water before migrating to the salt. The fish you caught was most likely chasing the fry of other fish that can be found throughout the Lake Washington system. Once these fish hit the salt and find food they grow quickly. A tagged 9 lb coho I picked up last summer had been released from the Quilcene hatchery in the spring of the previous year. As your fish still has its adipose fin, it is a good bet that it didn't come from the Issaquah hatchery like most of the juvenile fish we have been catching of late. Adult coho hit the Lake Washington system from summer through late December. Juvenile coho typically rear in the river/lake until at least the following spring after hatching. Their size strictly depends on how much food is available to them and some years are better than others. Lake Washington has a fairly dense intermediate sized food source in stickelback and smelt and some of the fish never migrate to the salt.

One thing you and other readers should take note of, with the exception of the Samammish Slough and the Cedar River, the remaining tributaries, in the Lake Washington system that the State opens during the summer months, are for anglers under the age of 15 only. If you are unlucky enough to cross paths with the King County Sheriff that patrols the lake, he's a real peach to deal with and doesn't give warnings.

[fisherben]

Thanks for the info on the fish! I never knew that the coho could get that big in so little time. Normally I usually don't pay attention to the catch regs when I C&R since I release my fish(unharmed), however now that I am aware of the age restrictions and seasons for those creeks I will keep that in mind! Thanks G-man!!