Effects of phytoplankton blooms on juvenile salmon in Cowichan Bay in 2014 and 2015.

As part of the Salish Sea Marine Survival Project, a pioneer research was initiated to study the effects of phytoplankton dynamics on wild juvenile salmon. During a 2 year observation period in Cowichan Bay we found strong evidence of phytoplankton blooms having impact on juvenile salmon. During high biomass blooms, Chinook salmon significantly reduced feeding with a two fold increase in the proportion of empty stomachs. Change in the behavior of Chinook salmon and a 25 fold increase in post pit-tagging mortality was also associated with a bloom of Heterosigma akashiwo. High concentrations of mechanically harmful Chaetoceros convolutus and C. concavicorne appeared to cause lesions and necrosis in salmon gills. These observations suggest that algal blooms and/or their absence in coastal waters could have profound impacts on juvenile salmon survival