C195,
the DH8D may be throttled back significantly in cruise if desired. Reducing to Long range cruise (which is the minimum allowed setting at my company) at ISA will show a bit below 50% torque and 208kIAS; fuel flow will be about 900 to 950 kg/h (compared to about 68%, 246kIAS and 1200kg/h at maximum cruise rating). This results in a TAS of 310kts versus about 360kts at maximum rated power.
I would expect a DH8D to use something between 950 and 1.000kg on such a route when using minimum power for cruise, possibly some kg less when climbing at maximum rate after departure. This of course assumes the lack of a headwind, in which case a reduction of climb IAS and cruise torque is often highly contraproductive and will increase both flight time and total burn.