Submitter: Mark Buecker
Community: Pitt Meadows
Date Submitted: January 5, 2011
The decline in salmon stocks in 2007 and 2008 is attributable to the increased temperature, dryness, erosion and turbidity resulting from the 2003 and 2004 wildfire seasons, some of the worst on record. Similarly, the very large salmon collapse in 1962 was caused by the 1958 fire season, the largest in BC's history. Evidence of the relationship between fire seasons and salmon declines is offered in the attached documents. Further research in the area of erosion and forest fires is necessary to protect aquatic ecosystems and, ultimately, salmon.
Turbidity From Large Wild Fire Seasons And Heavy Rain Events Are A Likely Cause Of The Pacific Sockeye Salmon Collapse
I did a presentation for my EVSC 401 class at SFU during the fall semester, on the Pacific Sockeye Salmon decline.
I found that the Fire seasons of 2003 and 2004 (some of the worst on record) were attributable to the declines in salmon stocks in 2007 and 2008 (see attachment “Relevant Parts Of My Presentation” for numbers). I also attributed the very large collapse in 1962 to the largest fire season in BC history of 1958.
The increased temperature, dryness (less refugia and reduced riparian cover over streams), and increase turbidity of the ash (ash is in my opinion is very angular and “sharp” to the gills of salmonids) is what caused the unexpected declines in these years.
The 2009 return of salmon can be attributed to the three turbidity events in late 2006 to 2007 late March. November 2006 was the worst turbidity event in Vancouver since the GVRD took over and caused a boil water advisory, also another occurred in December (these didn’t affect the salmon as they were not traveling to lakes or oceans at this time they travel usually in March). These two events might have weakened slopes and washed away less harmful debris (less sharp), revealing less weathered material (which is usually sharper).
But the most important occurred well the salmon smolts were leaving the lakes to the sea in late March. Smoltz are more vulnerable to turbidity than adults. Turbidity has many effects, some being increased susceptible to diseases, increased psychological issues, and break down of social structure (see attachment “Relevant Parts Of My Presentation” for numbers).
Examination of key years at the begging of the decline (1991,1992,1993,1994, see attachment “Additional Data” for numbers):
I noticed that when one would expect an increase in population, because favorable conditions were present (good population size for breeding), forest fires seem to explain why they do not and actually decline. The 1993 low forest fire season but still a decline could be for many reasons but might be that the fierce forest fire season of 1992 caused erosion problems the preceding year. There is some evidence of this which is, in the 1959 fire (after the very large 1958 season) season return in 1963 was down as well (lack of 1959 data prevents me from being assertive).
Although the declines in Pacific Sockeye Salmon might be explained in other ways, I’m pretty sure it’s the erosion factor that occurs after massive forest fires in combination with possible sharp ash reaching streams (also other erosion factors, such as heavy rain events).
If nothing else this helps to explain why projections for the 2007, 2008, and 2009 (2007 and 2008 because of large fire seasons 2009 because of heavy rain fall events) were so off. Also, the 2006 fire season was moderately high, but this is the whole province and over the entire year and therefore the timing and/or area burned might have negated effects on Pacific Sockeye Salmon in the Fraser River.
More studying must occur in the area of erosion (when are they likely, i.e. after a huge erosion event the next year erosion might decline or increase, we don’t know) and forest fires to better protect our aquatic ecosystems and ultimately our salmon.
I’ve attached relevant parts of my presentation (if explanation is needed I would be happy to explain).
I’ve attached also the most important articles I used in my research.
Thank you for reading,