Urinary phosphorus (P) excretion in freshwater rainbow trout in a metabolic chamber (Sugiura, 1998). Urine was continuously and quantitatively collected from a fish placed in a metabolic chamber of Smith (1967), using a catheter and small open-top vials positioned on a rotating disk. The fish was force-fed once every 24 hours, receiving 1% of its body weight (on a dry basis) from Day 1 to Day 6, using a glass plunger. The diet composition (dry weight basis) was: 35% egg white, 10% gelatin, 14% dextrin, 20% fish oil, 4% vitamin-mineral mix, 2% amino acid mix, and 14% cellulose, with additional 3.51% KH₂PO₄ and 4.21% CaCO₃. The total P content was 0.93%, and the total Ca content was 1.89%. Balance summary: Fish body weight: 366 g; Total P fed: 29.1 mg 24 h⁻¹; Total P excreted in feces: 2.29 mg 24 h⁻¹; Urine output: 13.0% of body weight 24 h⁻¹; Total P excreted in urine: 13.7 mg 24 h⁻¹; Total P retained by fish: 13.1 mg 24 h⁻¹ (0.374% of dry diet).