Massive exports could not stop an 81 per cent slump in first-half profits for Fortescue Metals Group (FMG).

Australia's third-biggest iron ore miner has recorded a first-half profit that is just a fifth of last year's result, bringing in $US331 million in the period.

The drastic drop was despite a massive lift in production and shipments.

The fall in profit came from a 17 per cent slip in revenue to $US4.86 billion, while a 53 per cent rise in iron ore shipments did not do enough to balance the books.

The future for FMG appears to hold only cuts and austerity, as spot iron ore prices have roughly halved in the last year from $US125 per dry metric tonne to $US65 per tonne at Chinese ports.

Fortescue has announced it will cut its capital expenditure by half - down to $US650 million - in response to poor prices.