My itinerary
As my family's stay was far too short (9 days) for a complete tour of this great country, we decided to confine ourselves to the southern part. Departing from Oslo, we headed west to Bergen and its fjords. Then, by leaps and bounds, we reached our starting point along the south coast, passing through Stavanger and Kristiansand.

Regulations
While fishing is an institution in Norway, it is no less regulated. For the sea, no permit is required, but there are legal catch sizes.
For freshwater fishing, however, you'll need a fishing permit, which sometimes differs from river to river or body of water to body of water. You can obtain information at a tourist office, a fishing store or at the water's edge (especially on salmon runs), where there are regular signs and sometimes even QR codes to pay for your day.

Sea fishing
Inshore fishing is special in Norway, as fjords and even rocky coasts give direct access to the deep, and it's not uncommon to cast in 30 meters of water from the shore.
I was very surprised (perhaps not informed enough!) to find that there was no tidal range and very little current. However, there are marked spots which you should identify to maximize your chances of catching a fish.
The easiest way is to observe the coastline and imagine that this relief extends underwater. In this way, each point deflects the little current that exists, but above all is synonymous with a change in depth, which is always conducive to the presence of fish. In addition, target the narrowest areas, notably between bridge piers or passages between islands. Once again, the existing weak current will be channeled and bring its share of food.
From the shore, catches are plentiful when you find the right spot. You can reasonably bet on catching fish ranging from 1 to 3 kg, or even more for those with a bit of luck.
You'll catch mackerel, of course, but also pollack, coalfish, cod and even a small halibut if you're touched by grace!

Freshwater fishing
As with the sea, freshwater fishing opportunities in Norway are endless. The country is dotted with rivers and lakes that are home to perch, pike, trout and, above all, the emblematic salmon. If there's one species you should try to catch during your stay, it's this one, because let's face it, in France, opportunities are pretty limited...
For perch and pike, the easiest way is to prospect reed beds and water lily beds.
In the river, for trout and salmon, alternate accelerating currents, calm waters sheltered by rocks and long flats. For salmon, be attentive and observant, you'll be able to observe them jumping. All you have to do is insist, vary your presentations and cross your fingers, but rest assured your chances of catching them are certain!