Diadromous fish

Very few freshwater fishes occur in Iceland, or only 7, and all are either diadromous (that is, can both live in fresh water and in the ocean) or have diadromous origins. This is of course because Iceland has been an island for a long time and classical freshwater fishes, such as carps and freshwater catfishes (not related at all to the marine catfishes found around Iceland), found in mainland Europe and North America cannot cross the marine barrier. However, diadromous fishes spend part of their life cycle in the ocean and can therefore cross it.

Diadromous fishes are further separated into anadromous and catadromous. Anadromous fish live as adults in the sea but breed in fresh waters, usually the juveniles also stay there. Catadromous fishes are the opposite; adults live in fresh waters but migrate back to the ocean to breed.

The best known anadromous species in Icelandic waters are the three salmonids, Atlantic salmon, brown trout and Arctic char, all described separately. The other four species are the three-spine sticklebacks (Gasterosteus aculeatus), small but very common fishes all around Iceland, both in shallow marine waters and in freshwater. The European eel (Anguilla anguilla) and the American eel (Anguilla rostrata) are catadromous and are both found in Iceland, the European eel being fairly common, especially in the southern lowlands. Finally, the flounder (Platichthys flesus) is a very recent arrival in Iceland.

These species are not of much commercial interest, except that eels are sometimes fished in traps for local consumption and the flounder might be fished if it becomes more abundant. Some lakes have been stocked with rainbow trout (Oncorhyncus mykiss), but they have not been known to spawn successfully in the wild. Pink salmon (Oncorhyncus gorbuscha) are occasionally fished in Icelandic rivers, but these are most certainly stray fishes from northern Russian rivers that have been stocked with this species. Rainbow trout and pink salmon both originate in the North Pacific.

The fisheries for the freshwater species are fundamentally different, as the freshwater fisheries are mostly managed by the private sector, the owners of the land, while marine fisheries are administered by the government. The utilization of the resources is also fundamentally different today; from the ocean, it is the products from the fishery that yield the value, while in freshwater fisheries it is the fishery itself, the catch is almost a nice bonus.

Editor