Okay, I was able to answer my question. I was incorrect. The movie "Andersonville" is based on diary of John Ransom (its online). The difference between Spragues experiences and Ransoms is the scope of the crimes by the gangs. Sprague called the gangs "Muggers" and Ransom called them "Raiders". Ransom never mentions the term "Fresh Fish" in his diary. Both men experienced military courts within the camps to keep order, except in Ransom's diary they put men to death at Andersonville, Sprague's courts could not. It is interesting that both men experienced such behavior by fellow POWs.