More efficient way to cook fresh caught fish while camping
As you will have the freshest fish possible and only limited equipment and ingredients in your camp, why not choose a preparation that is in its simplicity highlighting the fish, needs almost no equipment and creates no trash:

Plank cooking, also known as Loimulohi.

The cleaned fish, filleted or butterflied, is nailed on a wooden plank, either with ordinary nails or wooden pegs. Then the whole board is either stood up vertically around a (blazing) fire, leaned forward towards the fire or placed over the embers, depending on your preferences.

You can use basically every untreated, non-poisonous wood, in the Pacific North West, cedar is traditionally used because of the aroma it imparts.