Place the chillies, garlic, salt, cumin and coriander in a pestle and mortar and pound until smooth.
Add enough olive oil to make a paste.
Heat 15 ml oil in a heavy-based frying pan.
Spread the smooth paste over the fish and fry, skin side up, for three to five minutes depending on the thickness of the fillets.
Turn and continue to fry until cooked through.
Serve on a bed of couscous with lime wedges. Add freshly chopped coriander to the couscous for a wonderful colour and flavour contrast.
The spice rub is equally delicious on chicken pieces cooked on the braai.