Fines would go towards the Katmai Conservancy, a non-profit that looks after the running of the park.
The incident which happened in Autumn 2018 caused outrage and the men were eventually identified by the National Park Service Investigative Services, with help of the web camera footage which had been broadcasting online.
"The conduct of these three individuals not only endangered other visitors and wildlife officers at Brooks Falls, they also potentially endangered the life of the bears," said Attorney S. Lane Tucker for Alaska.
Had the indecent resulted in death or injury, Tucker argued it would have huge impact on tourism to the area and the animals would have to be destroyed.
The National Park Service were alerted to the incident by viewers of their 'bear cam' which was being broadcast live to YouTube. The men were later also identified on CCTV at a local bar, according to a NPS spokesperson.
"These individuals behaved carelessly and put themselves at great risk. Brown bears are fierce, territorial predators, especially when concentrated in order to feed on migrating salmon," said Mark Sturm, superintendent of Katmai National Park and Preserve. "Things could have easily ended very badly."