Well I missed two days of blogging - apologies to all of you out there waiting with bated breath for the next instalment. It's a sad one too. the story of the massive decline in wild salmon populations, caused almost exclusively by man.
West coast (of the USA) salmon have declined dramatically in the last three decades. There is no single factor one can point to given the complexity of their life cycle and the ecosystem in which they reside. It is only possible to highlight factors which have significantly affected their status.
Water storage, withdrawl, conveyance and diversions for agriculture and hydroelectric power have greatly reduced accesible habitat. Modification of river flows has altered water temperatures. Physical features such as dams, turbines and sluices have resulted in increased mortality for adults on their way up river and juveniles on their way down.
Land use such as industrial logging, road construction, urban development, mining and recreation have altered fish habitat quality and quantity. It is estimated than in the last two hundred years the lower 48 states have lost 53% of their wetland habitats.
Salmon have been and continue to be an important target species for recreational fishing througout their range. During periods of decreasing habitat recreational fishing has a much larger impact.
The introduction of non-native species and habitat modification has also increased predator populations. Terns and cormorants, sea lions and harbour seals are examples of potential predators.
In an attempt to mitigate the decline in salmon stocks extensive hatchery programmes have been implemented. While some of these appear to have been succesful, the impact on wild stocks is not well understood. Competition, genetic changes and disease transmission may impact the production and survival of wild salmon.
So - we don't really know what's happenning nor do we know what to do about it. Another example of man's inveterate desire to alter and mould nature to try and conform it to our will. It isn't ultimately going to work is it?