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THE IMPORTANCE OF HERRING AND OTHER
FORAGE FISH TO PACIFIC SALMON
QUESTIONS ADDRESSED DATA CONCLUSIONS
Determine an index of herring
recruitment and prey availability
to salmon and other predators.
Explore factors affecting herring
distribution and survival.
Determine the relationship
between recruitment of herring
and marine survival of Coho
and Chinook Salmon.
1992-2019 DFO juvenile Pacific
Herring and Nearshore Pelagic
Ecosystem Survey.
DFO trawl survey data including
stomach content data for juvenile
Coho and Chinook.
Year-round hook and line observa-
tions of Chinook and Coho diets
from Salish Sea Anglers.
Diet, size and growth of juvenile
Chinook caught by microtrolling
in the Gulf Islands.
Condition of juvenile herring in the
Strait has been high since 2007.
Length-weight residuals (condition)
increased during 1997-2012 and were
positive in 2005 and 2007-2017.
During the Salish Sea Marine Survival
Project, only the largest juvenile
Chinook appeared to be capable of
feeding on age-0 herring.
Feeding on herring appears related
to higher growth over the first
summer/fall, which may improve
winter survival
Anchovy have been abundant in the
Strait and have provided an alternate
food source since 2014.
BACKGROUND
Healthy forage fish populations are crucial for Coho and
Chinook which switch from feeding on invertebrates to fish
during their first summer at sea. Abundant forage fish may
also help reduce predation pressure on juvenile salmon
because other fish, marine mammals and birds consume
forage fish too. The forage fish community of the Salish Sea
is dominated by Pacific Herring, Pacific Sand Lance, and
various species of smelt. Anchovy have also been abundant
periodically, including since 2014 (the period of the Salish
Sea Marine Survival project).
In the Strait of Georgia (SOG), both juvenile Chinook
and Coho Salmon switch to feeding on herring during their
first summer. The relationship is complex: while abundant
Pacific Herring may inhibit juvenile Chinook Salmon growth
through competition, larger juvenile Chinook Salmon may
experience enhanced growth when Pacific Herring small
enough to utilize as prey are abundant. Understanding the
factors affecting the recruitment dynamics and growth of
herring in the SOG may be key to understanding the vari-
ability in the marine survival of Coho and Chinook Salmon in
the SOG.
The main objectives of this program were to estimate the
relative abundance and distribution of juvenile herring and
other pelagic fish in the Strait of Georgia, create an index
of potential prey availability to Coho and Chinook, and
determine why the forage fish community varies over time
and space.
