Charles Assimakopoulos, an owner, trainer, and breeder whose Yasou Stable Trust was a dominant presence on the New England racing scene for decades, died April 22 in Fitchburg, Mass., following a long illness. He was 83.As an owner, Assimakopoulos racked up 12 meet titles at Suffolk Downs in Massachusetts, and four at Rockingham Park in New Hampshire. He was also perennially among the top trainers at both tracks.Among his best runners was Prolanzier, whom Assimakopoulos owned and trained through 32 wins in 92 starts, from ages 3 to 11, for earnings of $485,459. Prolanzier, a Florida-bred, won nine stakes races at Suffolk and Rockingham, including two editions each of the Topsider Stakes, Waquoit Stakes, and Private Terms Stakes, all at Suffolk.Assimakopoulos also started the career of eventual Grade 2 winner Gander, racing him through the summer of his 4-year-old season for owner Gatsas Thoroughbreds before the horse was relocated to the barn of trainer John Terranova. Under Assimakopoulos’s watch, Gander became champion New York-bred 3-year-old of 1999, and he was the trainer of record for the first half of Gander’s campaign as the state’s horse of the year in 2000.Other runners of note owned and trained by Assimakopoulos include multiple stakes winners Co Art and Kayla’s a Gem.In total, Yasou Stable Trust won 531 races for earnings of $6,647,507. As a trainer, Assimakopoulos compiled 1,633 wins from 1979 and earned $17,661,238.Assimakopoulos was named to the New England Turf Writers Association Hall of Fame in 2010 as an owner and breeder. He retired from training in 2015.Assimakopoulos is survived by sons John and James Assimakopoulos, daughter Lisa MacAloney, six grandchildren, and a great-grandchild. John Assimakopoulos was a longtime assistant for his father’s training operation, and he now hangs his own shingle in Florida.Visiting hours for Assimakopoulos will be held May 20 at Lavery Chartrand Alario Funeral Home in Fitchburg from 4-6 p.m. Eastern.