I sent an email a while back to wdfw regarding Lake Sammamish Cutthroat and just got a response back from the Regional Fisheries Biologist. In summary, keeping cutthroat won't hurt the cutthroat populations, but eating many of them is not advised. The Lake WA advisory for cutthroat is > 12" no more than 1 meal per month, < 12" no more than 3 meals per month. You can see the rest of the advisories here.
http://www.doh.wa.gov/ehp/oehas/EHA_fish_adv.htm Thank you for your e-mail regarding cutthroat in Lake Sammamish. Unfortunately, we do not have harvest information specific to cutthroat trout. However, based on work conducted by other researchers (e.g., University of Washington, Tribal Governments, Federal agencies, etc.) it appears that the cutthroat population in Lake Sammamish is robust and the current level of harvest probably isn't significantly effecting the population. Regarding consumption of cutthroat trout; we are not sure if the contaminant load of Lake Sammamish cutthroat has been tested. There is currently an advisory for consumption of cutthroat harvested in Lake Washington and I'd recommend adhering to that advisory for Lake Sammamish fish. For more information on the Lake Washington advisory contact the local State health department.