The basics for our vision The Natural River.
There are about 8000 eggs in a 5 Kg hen salmon. During the development from egg to smolt there are many bottlenecks, like emerging from the gravel, enough food, winter survival, temperature for the different stages, predators, etc. We can say that 1 % survive from egg to smolt. A hen fish will then produce ca 80 smolt. In the sea the survival of the smolt varies from 1 to 10 %, a return of 0.8 fish in bad years and 8 for good years. The number of returning salmon varies with sea conditions around the carrying capacity of the river. A fair return can be good in bad sea condition but bad in good conditions. In the long run 2 are replaced by 2, the ones that reproduce are replaced. If too many salmon survived the river would be overcrowded, the river can’t support the numbers.
Many eggs are wasted. Clearly this is meant to be, but why. One answer is the different habitats that the salmon must pass through to return, river, fjord and sea. It requires skills that are different year to year, due to changing conditions. A salmon can’t contain all the possibilities to survive but there can be many individuals that together have the required abilities. The river train the different individuals or genes so that some will have the required skills to complete the life history. Some possibilities survive a year but next year a different set of skills may be required. The salmon do not know in beforehand what is coming and produce all the required genes and develop them in the river, thus the numbers. It is called Biological Diversity.
The salmon show plasticity and tries to adapt by passing on some memory of the present. If we change its habitat the salmon will develop other or fewer skills, pass the memory on to the offspring and lose possibilities to survive. One example is the hatchery where the salmon adapt to that environment. Another is optimized water power production of rivers which changes the river habitat. The management of salmon is to protect and restore the salmons Biological Diversity.
How do we give the salmon skills to survive its lifecycle. First, we recognize that the management of the river effects the salmon survival in the sea. We manage the river by removing obstacles for natural processes. By introducing new processes we will introduce new lack of diversity, increase natural processes and Biological Diversity will increase.