timing of spring phytoplankton blooms in southern Alaska and coastal British
Columbia has been correlated to the productivity of pink salmon in a recent
study sought to connect biological conditions in the ocean, specifically
phytoplankton, when juvenile salmon arrive, with the productivity, defined as
adults produced per spawner, of 27 stocks of returning adult pink salmon. Due
to the similarity of the migration and where the fish feed in the water column
when in saltwater, the researchers believe the findings very likely apply to
sockeye salmon, with a weaker link to chum salmon, as well.
the correlation between the timing of the spring bloom and the productivity of
the salmon is opposite depending on the location of where the bloom occurs
along an east-west line that splits southeast Alaska and the sea off British
study provides evidence that an earlier spring bloom is associated with higher
productivity for pink salmon stocks in Alaska and lower productivity for
British Columbia stocks,” said Michael Malick, a PhD candidate in the School of
Resource Management at Simon Fraser University in Vancouver, British Columbia.
the productivity for the southern stocks off British Columbia is strongest when
the bloom is later, the study says. It is widely thought that the first year a
juvenile salmon is in the ocean is a critical period that has a strong
influence on salmon abundance when they return to spawn as adults.
the timing of this spring bloom in the ocean helps to explain the variability
in returns of the salmon to their native streams to spawn, according to the
phytoplankton phenology to salmon productivity along a north/south gradient in
the Northeast Pacific Ocean,” was published online Jan. 7, 2015, in the
Canadian Journal of Fisheries and Aquatic Sciences (http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2014-0298#.VNQKrp3F9qU).
with Malick, authors are Randall Peterman, professor emeritus, and Sean Cox, associate
professor, both in the School of Resource Management at Simon Fraser
University; and Franz Mueter, associate professor, School of Fisheries and
Ocean Sciences, University of Alaska Fairbanks.
salmon of any type don’t feed directly on phytoplankton when they enter the
ocean, the spring bloom represents the base of the marine food chain and is an
important driver of groups higher on the food chain, such as zooplankton, which
pink and other species of salmon do feed on in the coastal environment, Malick
several reasons we discuss in the paper, it is likely that our results are
transferable to chum and sockeye salmon, which tend to have similar diets and
similar responses to changes in ocean conditions as pink salmon,” he said.
“It’s not clear how our results would transfer to chinook and coho salmon
though, which tend to have different diets (they tend to eat more fish)
compared to pink salmon in coastal environments.”
spring bloom in the coastal Northeast Pacific Ocean is driven by both
large-scale climate patterns and regional and local-scale physical
environmental conditions, the study says.
example, the bloom in the Gulf of Alaska is “correlated with the onset of water
column stability” and that is partly controlled by the strength of the Aleutian
low pressure system. But the bloom is also driven by local conditions, such as
sea surface temperature and sea surface salinity, in addition to being the
result of freshwater runoff in the spring.
this area, an earlier spring bloom is generally a more intense bloom and the
timing and phytoplankton biomass “are strongly correlated with yield and
productivity of certain marine populations,” the study says.
early bloom in the northern area tends to happen in warmer, wetter years
associated with the Aleutian low, higher zooplankton mass and increased salmon
an earlier spring bloom is also associated with water column stability in the
south, the stability is driven by thermal warming and reduced
upwelling-favorable winds, also associated with the Aleutian low, the study
says. However, these conditions are also associated “with increased predator
abundances, reduced zooplankton biomass, and decreased salmon productivity,”
the study says.
to the spring bloom timing caused by natural climate variability or by climate
change could potentially cause latitudinal shifts in salmon productivity,
according to the study.
is generally recognized that a warming climate will lead to an earlier onset of
spring conditions, including earlier timing of peak zooplankton biomass and
outmigration of pink salmon,” the study says. If the two aren’t in sync, then
it could lead to a northward latitudinal shift in pink salmon productivity.
added that the timing of the spring bloom has been shown to be sensitive to
changes in climate in some areas. That combined with the study results
“suggests that climate change could have important implications for Pacific
salmon if a warming climate causes systematic shifts in the timing of the
major result of this research is that the timing of ecological events, such as
the spring bloom, [is] important when trying to understand variability in
Pacific salmon returns. While this outcome is unlikely to have a direct
influence on the current management of wild Pacific salmon, it may have
relevance for salmon hatchery management where release timing can be altered,”
Malick said. “However, our focus in this study was on wild salmon, which limits
our ability to provide recommendations for hatchery practices.”