(1) Because the relationship between the swimming speed v(m/s) of salmon and the unit number q of fish's oxygen consumption can be expressed as a function v= 12log3Q 100,

So when Q=900, v = 12 log? 3900 100= 12log？ 39= 1 (m/s).

(2) When the swimming speed of salmon is 1.5m/s, let v= 1.5m/s, then 1.5 = 12log? 3Q 100, the solution is Q=2700 units.

Answer: (1) When a salmon consumes 900 units of oxygen, its swimming speed is1m/s. 。

(2) When the swimming speed of salmon is 1.5m/s, the unit number of oxygen consumption is 2700 units.