Well In terms of an exchange rate management policy, the Central Bank of Nigeria CBN has ONLY 2 main policy choices.
1. Devalue the Naira ie black market rate
Or
2. Defend the Naira ie Interbank rate
Defend means CBN gives out foreign reserves to banks to fund imports at official or subsidised rates, well below black market rate.
If exports fall, and CBN wants Naira to stay "strong", CBN taps reserves to fund Import/Export Window more and meet commitments
So ....devalue or defend?