Gaskell, 22, has found chances limited in 2013, while Howarth was the only Reds player to feature in all 29 of their matches last season.
Saints coach Nathan Brown said: “At this stage of his career Lee needs to be playing more regularly and with chances limited at present it made sense for him to go out on loan.
“We’re looking forward to watching him develop and I’m sure he will do a good job for Salford.
“Stuart has shown in his time at Salford that he is a capable and experienced player and will prove more than adequate cover for a multitude of positions.
“He will be put straight into the Good Friday squad and we are confident he will do well.”
Ironically, Howarth could make his debut against the team where he started his career, having come through the Wigan academy.
He has also played in Super League for Wakefield, making 21 appearances for the Wildcats in 2011.