Hal Clement posited schools of "pseudolife" fish processing seawater to extract gold/platinum and harvested by tenders in his short story "The Mechanic" --- it,

Hal Clement posited schools of "pseudolife" fish processing seawater to extract gold/platinum and harvested by tenders in his short story "The Mechanic" --- it, "Raindrop" and "Halo" are still relevant today and highly recommended.