Blend half the pineapple cubes in an electric blender, strain, keep the juice aside.
Dissolve the turmeric powder, red chili powder, fennel powder and ginger paste in a little water, keep aside.
Marinate the fish with a little turmeric and salt, keep aside.
Heat oil in a pan, shallow fry the fish, keep aside. (If the fish is very fresh, do not bother frying it.)
To the same oil, add the crushed cardamom, fennel seeds, bay leaves and green chillies, allow the spices to splutter.
Add the spice paste, saute for a couple of minutes till oil starts to release from the masala.
Lower the flame, gently pour in the pineapple juice, throw in the remaining pineapple cubes, cook for 3-4 minutes.
Add 1/2 a cup of warm water, gently place the fish in the curry. Add some more ginger paste and/or fennel powder if needed. Cook for a further 3-4 minutes.
Adjust seasonings. Serve hot with rice.