STEVENSON — William Haynes, one of roughly a dozen individuals implicated in 2017’s massive poaching investigation in Washington and Oregon, pleaded guilty Thursday morning to 15 charges related to illegally hunting big game with dogs and leaving the corpses to rot. Haynes, a Longview resident, will be sentenced on Feb. 28, but his plea in Skamania County Superior Court leaves only one major defendant in the Washington portion of the massive, high-profile case. For several minutes, Skamania County Superior Court Judge Randall Krog read off 15 charges spanning Haynes’ alleged illegal hunting activity from August 2015 and September 2016, each time asking Haynes for his plea.