To make the salad, halve the avocados, remove the stone and peel away the skin.
Roughly cut the flesh into 1cm (0.5in) dice, and place in a large bowl.
Squeeze the juice of 1 lime over the avocados, and stir gently.
Peel the mangoes and dice the flesh off the stone.
Place all of the salad ingredients in a bowl, stir them together and season with sea salt before adding the avocados and mangoes.
Season the fish with salt, lightly dusting the filleted side with flour. Melt the butter in a frying pan. Once bubbling, place the fillets in the pan floured side down. Season skin with pepper.
Fry gently for 4-5 minutes, then turn fish in the pan and remove from heat. Leave to stand for a further 2-3 minutes.
Place salad on a plate and serve fish alongside.
Drizzle any remaining butter in the pan over the fish. Serve.