After considerable research, it can be revealed that the fisheries agencies around the world have been lying to us about Salmon and Tuna.
They have maintained that the two are separate species, but this is in fact a lie.
Tuna are adult Salmon.
Salmon live in rivers, and when they reach a certain age go and live in the sea. Like lamb is more expensive than mutton, juvenile tuna (or salmon, as they prefer us to call it) is more expensive than adult tuna. Most people have noticed that tuna and salmon are interchangeable in recipes and both are so called 'dark' fish. The evidence is overwhelming.
In addition, anchovies and sardines are two other stages of this fish's life cycle.
If the fisheries people have been hiding this fact from us for so long, it suggests that the conspiracy runs deeper. Does your local chippy charge more for cod than haddock? Well, they are the same fish! Like pork and bacon are both from pigs, cod and haddock are different cuts off the same fish, what the industry calls internally coddock. The scraggy ends of coddock are termed Monk Fish. The coddock is the pig of the sea, as it also provides us with pollock and whitebait.
At the risk of incurring the wrath of the Fisheries Agency, a secret shadowy organisation that rules the world with an iron grip, it can finally be revealed that there are only two species of edible fish, the tuna and the coddock.