Chuck Morris, a musician best known as the percussionist for the band Lotus, and his son, Charley, have both been missing for nearly a week after they disappeared during a kayaking trip in Arkansas. 

Morris, 47, and his son vanished on Beaver Lake, a reservoir in the northwestern corner of the state, and were initially reported missing last Thursday, CBS Colorado reported. Authorities at the Benton County Sheriff’s Office enlisted help from local wildlife department officials as well as volunteer rescuers from the Cajun Coast Search and Rescue Team, who used boats to survey the expansive lake that covers more than 31,000 acres.

Chuck Morris of Lotus performs on stage at the Okeechobee Music & Arts Festival, Day 3, on March 5, 2016 in Okeechobee, Florida.

Photo by FilmMagic/FilmMagic for Okeechobee

By Tuesday, other members of Lotus, an electronic jam band based partly out of Denver and Philadelphia, said that Morris and his son were feared dead, and what began as a search and rescue effort had pivoted to focus on recovery.

“We were all hoping for a miracle, but at this point, the search for Chuck & Charley has moved to a recovery. With help from K9 teams, there is a probable location on the lake, but logistical challenges including temp, weather, and depth have prevented a recovery thus far,” the band wrote in a message shared to Twitter.

“It is unknown how long these efforts may take,” the message continued. “While we are deeply grieving, we plan to celebrate Chuck and Charley’s lives, our memories with them, and what they meant to so many people.”

A spokesperson for the Benton County Sheriff’s Office confirmed that responders had shifted to a recovery mission and “scaled back” resources in comments to CBS News on Wednesday morning.

“As of today we have scaled back the recovery operation today and only utilizing a few boats with k9 units attached,” said Lt. Shannon Jenkins, the public information officer for the sheriff, in an email. “Going forward, we will have our lake division scan the area regularly in hope to provide closure for the family.”

Members of the Cajun Coast Search and Rescue Team said in a Facebook live video shared on Tuesday that an estimated 30 people from the sheriff’s office and wildlife fishery were involved in the surveying effort earlier that day. They also said that trained K9 dogs had appeared to show interest in one section of the lake that could help them “come up with something conclusive” as search operations continued, but noted that efforts to locate Morris and his son had been hampered by severe weather conditions on the lake.

“We spent several hours on the water today and I can tell you that every obstacle that mother nature could throw at us, with the exception of rain, was thrown at us today,” said Tony Wade, director of operations for Cajun Coast Search and Rescue, specifically noting powerful winds and the lake’s tumultuous currents.

“This lake is a serious challenge to search but we’re doing everything we can,” Wade told CBS Colorado on Tuesday, adding that water temperatures in Beaver Lake were in the 30s and 40s over the last few days. It is impossible to survive for more than a couple of hours while submerged in water that cold.

“You’d instantly go into shock,” Wade said. “This is 100% a recovery.”