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This study captured evidence of the direct effects of
HABs on wild juvenile salmon in the Strait of Georgia.
From the 2014-2017 Cowichan Bay juvenile salmon
study, we observed reduced feeding in juvenile salmon
(empty stomachs in >50% of fish caught) and changes
in their diet during high algae biomass events; evidence
of gill damage confirmed by specific histopathology
following high levels of mechanically harmful diatoms;
and liver and brain damage, and signs of starvation
during moderate toxic algae levels. During the 2014
Heterosigma akashiwo bloom in Cowichan Bay, we
observed lethargic behaviour in chinook and a dramatic
increase in post tagging (PIT tags) mortality during purse
seine activities.
High resolution Citizen Science monitoring confirmed
the absence of major Heterosigma akashiwo blooms
in the Strait during 2015-2017. This is an unexpected
result as over 15 years prior, H. akashiwo bloomed in
the Strait every year. However, blooms of H. akashiwo
were recorded in 2014 during the pilot juvenile salmon
studies in Cowichan Bay and in 2018 by the PSF Citizen
Science Program. These contrasting results could help in
determining the possible role of H. akashiwo blooms on
overall juvenile salmon survival in the Strait.
Preliminary results based on the Citizen Science sampling
of phytoplankton and zooplankton in the Malaspina
Strait area indicate that biomass of large calanoid
copepods and euphausiids was significantly positively
correlated to the relative abundance of diatoms. These
analyses of the important links between phytoplankton
and zooplankton communities are ongoing.
SIGNIFICANCE
Thousands of water samples were collected over 2015-
2018, and we now have unprecedented, high-resolution
data on phytoplankton dynamics in the Strait of Georgia.
Multi-year data on harmful algae species and their
environmental preferences are being analyzed.
Preliminary results indicate a strong link between
HABs and environmental conditions of the Strait.
SSMSP has provided the first documented evidence
of the direct effects of HABs on juvenile salmon
in the Strait of Georgia. We observed effects of harmful
algae on juvenile salmon in Cowichan Bay in 2014-2016
and the effects were similar to those confirmed from
pen-reared salmon worldwide.
See our Facebook site:
" Phytoplankton-Citizen
Science Program".
Figure 1. Occurrence of two harmful algal species as related to environmental conditions of salinity and water temperature.
Graphs provided by Svetlana Esenkulova, PSF.
Rhizosolenia setigera
Salinity
(ppt)
Alexandrium spp.
35
30
25
20
15
10
5 10 15 20 25
Water Temperature (C)
Salinity
(ppt)
35
30
25
20
15
10
5 10 15 20 25
Water Temperature (C)
Figure 2. Noctiluca scintillans bloom from southern Vancouver
Island, May 2018. Blooms produce ammonia and cause hypoxia.
Credit: Dr. M. Costa UVic.
