The immediate alternative that came to my mind is trucking. I have a relative who pivoted from factory work into trucking and working with heavy machinery in his 50's, after the factory jobs dried up. Though he definitely had hard times, it is certainly doable and beats dying or getting crippled working for pennies.
Though far from a cushy job, trucking seems comparable to fishing (e.g. you're away from home for a long periods, doesn't require much education) without the danger and backbreaking nature of the work.