Fraser Valley Stream Nutrient Enrichment
The loss of aquatic productivity has resulted from dam impoundment, riparian logging, and reduction in
salmonid escapement. Salmonid species spend the largest portion of their adult life developing in salt water
environments before returning to their natal freshwater streams to spawn and die. This life cycle provides an
ecologically important process of delivering marine-derived nutrients to the freshwater aquatic and terrestrial
ecosystems, providing links between ecosystems, playing an important role in maintaining ecosystem health,
and having significant implications for conservation and biodiversity of freshwater flora and fauna.
The recent downturn in ocean productivity and survival has resulted in reduced salmon escapement. This loss of
essential aquatic nutrients (nitrogen and phosphorous) in the form of salmon carcasses, has particular
consequences on juvenile salmonid survival that rear for 1 to 4 years in freshwater ecosystems. Adequate levels
of these limiting nutrients are needed by lower trophic-level organism, which then relay the nutrients up the
food chain; periphyton (algae) growth increases, increasing insect growth and abundance, which are then fed
upon by juvenile fish. Their survival is strongly affected by the concentrations of these nutrients because faster
growing or larger juveniles more successfully overwinter during major fall-winter flood events, thus increasing
smolt production, marine survival and ultimately escapement.
To compensate for low freshwater productivity, BCCF fisheries technicians, with the assistance from various
volunteer groups, added slow-release fertilizer to 6 nutrient-poor streams in the Fraser Valley. Bi-weekly
monitoring of field parameters, water chemistry, and algal accumulation was performed throughout the
summer growing season and juvenile fish assessment was performed in the fall. Results of the project showed
there was an average increase of 212% in algal growth and fish that were 76.6% heavier in fertilizer reaches
compared to unfertilized reaches.