I could fish you could fish he could fish we could fish you could fish they could fish
V-ing form
I could be fishing you could be fishing he could be fishing we could be fishing you could be fishing they could be fishing
Perfect
I could have fished you could have fished he could have fished we could have fished you could have fished they could have fished
V-ing perfect
I could have been fishing you could have been fishing he could have been fishing we could have been fishing you could have been fishing they could have been fishing
Negation
Simple form
I couldn't fish you couldn't fish he couldn't fish we couldn't fish you couldn't fish they couldn't fish
V-ing form
I couldn't be fishing you couldn't be fishing he couldn't be fishing we couldn't be fishing you couldn't be fishing they couldn't be fishing
Perfect
I couldn't have fished you couldn't have fished he couldn't have fished we couldn't have fished you couldn't have fished they couldn't have fished
V-ing perfect
I couldn't have been fishing you couldn't have been fishing he couldn't have been fishing we couldn't have been fishing you couldn't have been fishing they couldn't have been fishing
Interrogative form
Simple form
could I fish? could you fish? could he fish? could we fish? could you fish? could they fish?
V-ing form
could I be fishing? could you be fishing? could he be fishing? could we be fishing? could you be fishing? could they be fishing?
Perfect
could I have fished? could you have fished? could he have fished? could we have fished? could you have fished? could they have fished?
V-ing perfect
could I have been fishing? could you have been fishing? could he have been fishing? could we have been fishing? could you have been fishing? could they have been fishing?
Interro-negative form
Simple form
couldn't I fish? couldn't you fish? couldn't he fish? couldn't we fish? couldn't you fish? couldn't they fish?
V-ing form
couldn't I be fishing? couldn't you be fishing? couldn't he be fishing? couldn't we be fishing? couldn't you be fishing? couldn't they be fishing?
Perfect
couldn't I have fished? couldn't you have fished? couldn't he have fished? couldn't we have fished? couldn't you have fished? couldn't they have fished?
V-ing perfect
couldn't I have been fishing? couldn't you have been fishing? couldn't he have been fishing? couldn't we have been fishing? couldn't you have been fishing? couldn't they have been fishing?