Fisheries | www.sheries.org 465
© 2019 American Fisheries Society
Disturbance in the
Cheryl A.Morgan | Cooperative Institute for Marine Resources Studies,Oregon State University, Hateld Marine Science Center,
2030 Southeast Marine Science Drive, Newport, OR 97365. Email: firstname.lastname@example.org
Brian R.Beckman | National Marine Fisheries Service,Northwest Fisheries Science Center,Environmental and Fisheries Sciences
Division, Seattle, WA
Laurie A.Weitkamp | National Marine Fisheries Service,Northwest Fisheries Science Center,Conservation Biology Division,
Kurt L.Fresh | National Marine Fisheries Service,Northwest Fisheries Science Center,Fish Ecology Division (retired), Seattle, WA
Fisheries | www.sheries.org 465
© 2019 American Fisheries Society
Photo credit: NOAA Fisheries/
Oregon State University
466 Fisheries | Vol. 44 • No. 10 • October 2019
An extended marine heat wave occurred across the North Pacic during 2014–2016, including the formation of the warm “Blob”
followed by a strong El Niño in 2016. Coincident with this marine heat wave, we documented unprecedented biological changes
in plankton and nekton in the Northern California Current (NCC) within pelagic surveys conducted over 20years (1998–2017).
The recent warm period was dominated by warmwater gelatinous invertebrates and shes, some of which were previously either
extremely rare or absent. Mixing of organisms originating from more southern or western regions with those previously present
in the NCC may have resulted in novel and unpredictable trophic interactions that produced some of the observed changes in
relative abundance. Continued long- term monitoring is needed to determine whether this is a temporary ecosystem disturbance
or a fundamental change in the very productive NCC upwelling region.
The Northern California Current (NCC) ecosystem (from
the Canadian border to Cape Blanco, Oregon) has undergone
a great deal of oceanic variability over the past 20years, in-
cluding a strong El Niño in 1998, a strong La Niña in 1999, a
Pacic Decadal Oscillation (PDO) regime shift during 1998–
2002 (Peterson and Schwing 2003), and a much- delayed spring/
summer upwelling period in 2005 (Lindley etal. 2009). These
oscillations between warm and cool periods have resulted in
shifts in abundance of many commercially important species,
including squid, hake, rocksh, and juvenile salmonids.
In fall 2014, an extreme warming of coastal waters oc-
curred as a large parcel of anomalously warm water—the so-
called “blob”—moved eastward and caused a sudden increase
in coastal temperatures (Bond etal. 2015). The warm Blob
formed in the Gulf of Alaska during the winter of 2013–2014
and generally persisted in the Northeast Pacic through 2016,
although brief periods of cooling occurred during May–June
2015 following strong equatorward winds and upwelling
(Peterson et al. 2015, 2017). The blob was immediately fol-
lowed by a strong El Niño event in 2015–2016 (Jacox etal.
2016). These oceanographic phenomena resulted in a pro-
longed marine heat wave throughout the NCC during 2014–
2016 (Di Lorenzo and Mantua 2016; Gentemann etal. 2017).
This heat wave resulted in shifts in the occurrence and abun-
dance of a broad range of taxa, including copepods (Peterson
et al. 2017), ichthyoplankton (Auth etal. 2017; Daly et al.
2017), squid (Sakuma et al. 2016), gelatinous invertebrates,
krill and shrimp (Sakuma et al. 2016; Peterson et al. 2017;
Brodeur etal., 2019), and shes (Leising etal. 2015; Sakuma
etal. 2016). Trophic shifts were also evident in juvenile salmon
diets (Daly etal. 2017).
We collected physical and biological data, including plank-
ton and pelagic nekton, on the same coastal grid from central
Oregon to the Washington–British Columbia border over a
20- year period from 1998 to 2017. This allowed us to devel-
op an oceanographic and biological baseline for the pelagic
ecosystem of the NCC. We documented unique abundance
variations within our 20- year time series, with effects at all tro-
phic levels. Unlike other recent publications, our data indicate
that biological disturbances continued through 2017, after
cessation of surface manifestations of the blob. This report
describes effects of the recent marine heat wave on the NCC
pelagic ecosystem and the status of the post- Blob NCC eco-
system. Because of impacts on larval and juvenile shes, we
expect marine heat wave effects to continue for several more
We obtained information from surveys conducted over
the continental shelf, 1.9–56.0km (1–30 nautical mi) offshore
of Washington and Oregon, USA, in late June 1998–2017.
During each survey, we sampled ve to seven xed stations
along each of ve to eight transect lines perpendicular to the
shore between the northern tip of Washington (48°13.7’N)
and Newport, Oregon (44°40.0’N; Figure 1). In this paper,
we summarize sampling and analysis methods used for these
surveys, but more detailed descriptions of these methods are
provided by Brodeur etal. (2005), Morgan etal. (2005), and
Peterson etal. (2010).
At each station, we sampled temperature, chlorophyll- a
concentration, zooplankton, and nekton. Temperature was
measured with a conductivity–temperature–depth instru-
ment to within 5m of the bottom or a depth of 200 m, and
chlorophyll- a samples were collected at a depth of 3 m using
a Niskin bottle. Temperatures for each station were aver-
aged over the top 20m of the water column that the trawl
sampled. Zooplankton collections were made with either a
1.0- m- diameter ring net (1999–2000) or a 0.6- m- diameter
bongo net (2001–2016), both of which were tted with 335-
μm mesh and a General Oceanics owmeter to estimate the
water volume ltered. Plankton nets were shed by letting out
60 m of cable and immediately retrieved at 30m/min while
being towed at 3.704km/h (2 knots). The maximum depth
Figure 1. Locations of Oregon–Washington coastal stations
included in the analysis for plankton (white) and pelagic nek-
ton (white and yellow).
Fisheries | www.sheries.org 467
shed was 20–30 m. We did not include plankton samples
from 1998 and 2017 in our results, as samples were taken at
only a few stations in 1998 and those from 2017 have not yet
Fish and invertebrate nekton were sampled using a Nordic
264 rope trawl (Nor’Eastern Trawl Systems, Bainbridge
Island, Washington) towed to sample the upper 20m of the
water column for 15–30min at approximately 6.5km/h. Only
stations that were sampled during the day, over the continen-
tal shelf (≤200- m water depth), and in at least 10 of the study
years were included in our analyses. We did not include jelly-
sh data from 1998, since jellysh occurrence was not reliably
recorded. We report only on species that exhibited signicant
changes during the blob period compared to previous years.
Our report consists of simple estimates of abundance
for the biological organisms of interest. Our evaluation of
interannual variation in abundance is also simple. We start-
ed by generating an overall mean abundance (grand mean
[GM]) and variance (SD [grand]) based on the average of 20
individual annual means (AMs; 1998–2017; see below). For
each year of sampling, we then determined the number of
SDs (grand)between the AM and the GM. All calculations
were performed using Statgraphics Centurion version 17.1
(StatPoint Technologies, Inc., Warrenton, Virginia). We evalu-
ated the abundance of organisms found in each year in refer-
ence to the number of SDs between the GM and the AM, and
we designated these yearly abundance estimates as follows:
typical (AM<1 SD from the GM), notable (AM>1 SD to 2
SDs from the GM), exceptional (AM>2 SDs to 3 SDs from
the GM), or extreme (AM>3 SDs from the GM).
Abundance was calculated differently for zooplankton
and nekton. Total abundance of each zooplankton species
caught in each haul was calculated using counts and water
volume ltered, converting to biomass by using length- to-
mass regressions and literature values (Morgan etal. 2005),
and then standardizing to units of milligrams of carbon per
cubic meter (mg C/m3). Total abundance of each nekton
species caught in each haul was either (1) determined direct-
ly from a total count of individuals or (2) estimated from
the total weight caught, based on the number of individuals
in a weighed subsample of that haul. Trawl catches of each
species at each station were standardized to linear densi-
ty by dividing station catch by the distance of the tow, as
determined by a Global Positioning System receiver. After
standardizing for distance, densities were log10(x+1) trans-
formed (log10[number/km+ 1]) to make the data easier to
visualize, interpret, and compare.
We used large- scale indices of ocean conditions, including
the PDO and the Oceanic Niño Index (ONI), to place local-
scale phenomena within a larger- scale mechanistic picture
and to provide a framework in which to examine physical phe-
nomena and lagged biological responses (Mantua etal. 1997;
Fisher etal. 2015; Peterson etal. 2017). Positive PDO values
were associated with relatively warm ocean conditions in our
region. Similarly, positive ONI values—indicative of El Niño
events on the equator—were also often associated with warm-
ing of the NCC. For our study, the PDO was reported as an
average of May and June values for each year (data available
from the Joint Institute for the Study of the Atmosphere and
Ocean, University of Washington: http://jisao.washington.
edu/pdo/PDO.latest.txt), and the ONI was reported as an
average of November–January and December–February val-
ues for each year (data available from the National Weather
Service’s Climate Prediction Center: origin.cpc.ncep.noaa.
RESULTS AND DISCUSSION
Physical Conditions in the Northern California Current
Temperatures in the NCC have been unusually warm since
2014 (Bond etal. 2015; Peterson etal. 2015). This was reect-
ed by the strongly positive PDO during 2014–2016, which
was the longest period of positive PDO in our time series
(48 months; January 2014–December 2017; Figure 2), and
by the highly positive 2016 ONI value, which reected the ex-
tremely strong El Niño at the equator (data from the National
Weather Service’s Climate Prediction Center: http://origin.cpc.
v5.php). Despite overall warmer temperatures documented in
the NCC due to the warm Blob (Bond etal. 2015; Peterson
etal. 2015), the upper 20- m temperatures in June during our
2014–2016 surveys were not unusually high; this was due to
short periods of upwelling prior to the surveys (data available
from the National Marine Fisheries Service’s Pacic Fisheries
Environmental Laboratory: https://www.pfeg.noaa.gov/prod-
NA.html; Figure 2). However, the complete monthly time
series in this region from 2014 to 2016 did show that tempera-
tures in the upper water column were elevated (Leising etal.
2015; McClatchie et al. 2016; Peterson et al. 2017). Finally,
while physical oceanographic indicators suggested a return
to neutral ocean conditions in summer 2017 (PDO; Peterson
etal. 2017), temperatures in our survey area were still high.
Biological Patterns of Change
In 2014, we observed biological changes coinciding with de-
velopment of the offshore blob and a positive PDO (Figure2).
For example, in June 2014, the chlorophyll- a concentration was
rated as exceptional and was one of the three highest values in
the time series. Similarly, Peterson etal. (2017) also observed
high chlorophyll- a concentrations in June 2014 during more
frequent sampling off Newport, Oregon. Among the animals
sampled, both California market squid Doryteuthis opalescens
and furcilia- stage larval North Pacic krill Euphausia pacica
had notable deviations in abundance and were more numerous
than in the previous 15years (Figure2).
In 2015, the abundances of more species deviated mark-
edly from their 20- year mean values (Figure2; Table1). The
deviation in biomass abundance of North Pacic krill furcilia-
stage larvae was exceptional, and for Pacic sand crab Emerita
analoga zoeal- stage larvae, the deviation was notable. Both
species were much more abundant than they had previously
been in the time series. Abundances of all three common jel-
lysh species changed markedly but differed in their direction
of change. The deviation in abundance of the normally scarce
water jellysh Aequorea spp. was exceptional, and it became
the most abundant jellysh in our catches. In contrast, the gen-
erally most common jellysh, the Pacic sea nettle Chrysaora
fuscescens, had notably lower abundances and was nearly ab-
sent from our samples. The deviation in abundance of egg- yolk
jellysh Phacellophora camtschatica was notably high, and this
species became more abundant than in previous years. Finally,
the abundances of three nektonic species increased. Although
only the California market squid was characterized by a no-
table deviation in abundance, Pacic Pompano Peprilus simil-
limus and Jack Mackerel Trachurus symmetricus abundances
were higher than in any of the 8 previous years.
468 Fisheries | Vol. 44 • No. 10 • October 2019
In 2016, 13 species had notable to extreme deviations in
abundance (Figure2; Table1), which occurred during the pe-
riod spanning the blob and following a winter with strongly
positive sea surface height anomalies and strong poleward ow
(Peterson etal. 2017). Two zooplankton species—Pacic sand
crab (zoeae) and North Pacic krill (furciliae)—had exception-
al deviations in abundance. Pacic sand crab zoeal biomass
was higher than in any previous year, while North Pacic krill
furcilia biomass was higher than in all previous years except
2015. Two jellysh species—the water jellysh and Pacic sea
nettle—had exceptional deviations in abundance, whereas the
egg- yolk jellysh had an extreme deviation. Egg- yolk jelly-
sh numbers were higher in 2016 than in any previous year;
water jellysh numbers were higher than in all previous years
except 2015; and Pacic sea nettle numbers were lower than
in all but two previous years (2000 and 2014). Three nektonic
species had notable deviations in abundance: California mar-
ket squid, Pacic Chub Mackerel, and yearling Coho Salmon
Oncorhynchus kisutch. Four nektonic species had extreme de-
viations: juvenile rocksh Sebastes spp., Pacic Pompano,
young- of- the- year (age- 0) Pacic Hake Merluccius productus,
and yearling Chinook Salmon O. tshawytscha. One nektonic
species—the Jack Mackerel—had an exceptional deviation.
California market squid, yearling Coho Salmon, and yearling
Chinook Salmon declined in abundance, whereas the other ve
nektonic species were more abundant than in any previous year.
In 2017, the chlorophyll- a concentration had a notable de-
viation, representing the lowest chlorophyll- a value obtained
during the 20- year time series. Five species had notable to ex-
treme deviations in abundance. The most surprising extreme
Figure2. Variables included in the analysis: large- scale physical indices (teal), average temperature (°C) in the top 20m (red),
chlorophyll- a concentration (μg/L; green), biomass of two plankton species (mg carbon/m3; purple), and surface trawl catches
(log10[number/km+1]) of jellysh (cyan), pyrosomes (pink), squid (orange), and sh (blue). Circles indicate the June average for
each year; bars represent±1 SE. The right y- axis and the corresponding horizontal lines indicate the number of SDs from the
grand mean (dark- red short dash=±1 SD; dark- red long dash=±2 SDs; light- gray long dash=3–6 SDs). The three warm periods
(1998, 2005, and 2014–2016; described in this paper) are shaded in light gray. The plots of Pacic Chub Mackerel and Pacic Hake
are total catch, with the smaller insets showing only young- of- the- year (YOY; i.e., age 0) catches for those species. The age- 0
(YOY) insets follow the same format as other plots, but year shading and SD labels are not shown.
Fisheries | www.sheries.org 469
deviation was the rst- ever occurrence of the colonial gelat-
inous tunicate Pyrosoma atlanticum, which was extremely
abundant throughout our entire survey area. Two other nek-
tonic species, yearling Coho Salmon and yearling Chinook
Salmon, had notable deviations in abundance and declined
to the lowest numbers obtained during the 20- year time se-
ries. Two additional nektonic species—the Pacic Pompano
and Jack Mackerel—had exceptional deviations in abundance,
with Pacic Pompano numbers being the second- highest ob-
served and Jack Mackerel numbers being the highest observed
during the 20- year time series.
Potential Mechanisms Leading to Changed Abundance
Multiple physical and ecological mechanisms are likely re-
sponsible for the variations in abundance documented among
many species (Table2). Although the survey was not designed
to determine the mechanisms that caused these variations, we
can make inferences based on three ecological and organis-
mal traits. First, plankton drift passively; as such, when water
masses are transported from south to north or from west
to east, the distribution of planktonic organisms changes.
Second, nekton can actively swim against currents and can
thus change their distribution in response to local tempera-
tures and seek out thermally preferred water masses. Third,
changes in abundance may be in response to changes in local
processes that regulate population abundances (e.g., repro-
duction and predation). These mechanisms are not mutual-
ly exclusive and probably do not represent a complete list of
possible processes. Moreover, in most cases, more than one
mechanism likely led to the patterns of change we observed
Planktonic water jellysh, egg- yolk jellysh, and Pacic
sand crab larvae are normally associated with warmer waters
to the south of our study area and/or offshore (Shenker 1984;
Suchman and Brodeur 2005). High abundances of these spe-
cies in our catches from 2014 to 2016 suggest northward and/
or eastward transport, corresponding with warmer southern
or offshore waters moving onshore (Gentemann etal. 2017).
Other planktonic species, such as copepods, have demonstrat-
ed similar patterns of unusual advection from southern and
offshore waters into the waters off central Oregon during this
same time period (Peterson etal. 2017). Northward shifts in
the distribution of these species have been also reported during
other El Niño events (Pearcy and Schoener 1987; Pearcy 2002;
Brodeur etal. 2005).
Thermal preferences, paired with spatial changes in water
temperature, may result in active migration by some species
from south to north or from west to east. For instance, the
California market squid, Pacic Pompano, Jack Mackerel,
and Pacic Chub Mackerel Scomber japonicus are normally
found in warmer southern waters and were observed in high
abundances during the warm water years since 2014. Other
studies have documented similar changes in the distribution
of these species during previous strong El Niño years (Pearcy
and Schoener 1987; Pearcy 2002; Brodeur etal. 2005).
We sampled only the top 20m of the water column with
the trawl and plankton nets during this survey. Therefore, we
cannot exclude the possibility that changes in abundance of
some organisms captured by our gear were due to changes in
their vertical distribution within our study area rather than
horizontal transport or active migration into the study area
from other locations. For example, some sea nettle species are
known to undergo diel vertical migration, although this be-
havior has not been documented for the species in our region
(Suchman and Brodeur 2005; Suchman etal. 2012), and juve-
nile Chinook Salmon may move deeper in the water column
Table1. Number of standard deviations (SDs) by which the annual mean (AM) was above or below the grand mean (GM) for each variable or spe-
cies examined, 2014–2017 (notable: AM>1 SD to 2 SDs from the GM; exceptional: AM>2 SDs to 3 SDs from the GM; extreme: AM>3 SDs from
the GM). Red indicates positive SDs; blue indicates negative SDs. “NA” indicates that data for the variable were not available in the specied
Variable or species 2014 2015 2016 2017
Oceanic Niño Index +2
Pacic Decadal Oscillation +1 +1 +2
Temperature, top 20m
Chlorophyll a+2 −1
North Pacic krill Euphausia pacica +2 +2 NA
Pacic sand crab Emerita analoga +1 +2 NA
Water jellysh Aequorea sp. +2 +2
Pacic sea nettle Chrysaora fuscescens −1 −1
Egg- yolk jellysh Phacellophora camtschatica +1 +3
Colonial gelatinous tunicate Pyrosoma atlanticum +4
California market squid Doryteuthis opalescens +1 +1
Juvenile rocksh Sebastes spp. +4
Pacic Pompano Peprilus simillimus +3 +2
Yearling Coho Salmon Oncorhynchus kisutch −1
Yearling Chinook Salmon O. tshawytscha −1
Jack Mackerel Trachurus symmetricus +2 +3
Pacic Chub Mackerel Scomber japonicus (age 0) +4
Pacic Chub Mackerel +1
Pacic Hake Merluccius productus (age 0) +4
470 Fisheries | Vol. 44 • No. 10 • October 2019
in response to warmer surface water (Orsi and Wertheimer
1995). However, we currently lack the data to directly test for
changes in depth distribution.
Information from other studies suggests that local pro-
cesses rather than different migration patterns may have been
responsible for the low abundance of juvenile Coho Salmon
and Chinook Salmon in our catches during 2017. Juvenile
Coho Salmon are not known to change depth preference in
response to warm water (Orsi and Wertheimer 1995; Beamish
etal. 2007, 2018), yet abundance trends for this species were
similar to those for juvenile Chinook Salmon in our study.
In contrast to the low catches in our coastal samples, which
mostly consist of Columbia River sh (Van Doornik etal.
2007; Teel etal. 2015), abundances of both juvenile Coho
Salmon and Chinook Salmon in the Columbia River during
2017 were at least average based on Bonneville Dam smolt
counts (the source of most of the juvenile salmon in our
survey; Fish Passage Center 2017) as well as estuary purse
seine smolt catches (L.A.W., unpublished). We also conduct
a separate survey in May, as smolts are entering the ocean
and before any potential changes in northward migratory ten-
dency could change their abundance. Our catches of juvenile
salmon of both species in May 2017 were quite low relative
to previous May survey catches (Morgan etal. 2017), which
have been conducted since 1999 (Jacobson etal. 2012; Teel
In contrast to Coho Salmon and Chinook Salmon, the
notable and extreme abundance increases in Pacic sand crab
larvae that were observed in 2015 and 2016, respectively, were
likely due to both local processes and northward transport.
Adult Pacic sand crabs live in the wash zone of sandy beach-
es, spawn in summer and fall, and produce larvae that are
planktonic for approximately 4months (Johnson 1939; Efford
1970, 1976). Larval Pacic sand crabs in our catches had a
bimodal age distribution caused by the presence of both early
(zoeal stage I [ZI]) and late- stage (ZV) larvae, with both stages
sometimes present in the same sample. We never found any
intermediate- stage (ZII–ZIV) larvae. We assume that ZI lar-
vae represented local production of eggs, as these larvae were
too young to have undergone long- range transport. The pres-
ence of older, ZV larvae, coupled with the absence of ZII–ZIV
larvae, indicates that the ZV larvae were transported from the
south, as was suggested to have occurred during other warm
periods, such as the El Niño of 1997–1998 and the warm peri-
od of 2004–2005 (Sorte etal. 2001; Figure2).
The rst observation of age- 0 Pacic Hake in our survey
occurred in June 2016. During February 2016, Auth et al.
(2017) found larval Pacic Hake at every station from 64.82
to 194.46 km (from 35 to 105 nautical mi) off the coast of
Newport, Oregon, 4months prior to and well offshore of our
sampling. This indicates that age- 0 Pacic Hake were relatively
abundant off the Oregon and Washington coasts in 2016. Since
this species usually spawns further south (i.e., off California;
Ressler etal. 2007), the presence of age- 0 Pacic Hake sug-
gests that spawning may have shifted northward. Similarly,
increased abundance of age- 0 Pacic Chub Mackerel in our
June 2016 survey may have been due to a northward shift in
adult distribution and spawning (Auth etal. 2017).
Comparisons with Other Studies
Since different ocean sampling studies may have dissimi-
lar objectives and methods, using results from these studies to
create a coherent picture of the NCC during the recent ma-
rine heat wave is much like the classic parable of blind people
studying an elephant: each person touches a different part of
the animal and thus describes a different creature. We suggest
that common trends across studies may reect large- scale pat-
terns, whereas differences among studies may simply be due to
differences in local distribution, sampling design, or method-
ology; alternatively, they may reect real differences.
Table2. Description of the persistence of a given species within our 20- year survey (continuous, sporadic, or novel during the marine heat wave
of 2014–2017) and change in abundance during the marine heat wave (increase or decrease). Also provided are a description of whether the
organism drifts with currents (plankton) or can swim against currents (nekton), inferred changes in spatial distribution during the marine heat
wave, and whether changes in abundance during the marine heat wave might be attributed to local ecological processes. A question mark indi-
cates that changes in abundance might be due to a change in depth distribution, but we had no data with which to test that possibility.
Inferred distribution change
Euphausia pacica (larvae) Continuous Increase Plankton ✓
Pacic sand crab (larvae) Sporadic Increase Plankton ✓ ✓
Water jellysh Continuous Increase Plankton ✓ ✓
Pacic sea nettle Continuous Decrease Plankton ?✓
Egg- yolk jellysh Continuous Increase Plankton ✓ ✓
Pyrosoma atlanticum Novel Increase Plankton ✓ ✓ ✓
California market squid Continuous Increase Nekton ✓
Juvenile rocksh Continuous Increase Nekton ✓
Pacic Pompano Sporadic Increase Nekton ✓
Yearling Coho Salmon Continuous Decrease Nekton ?✓
Yearling Chinook Salmon Continuous Decrease Nekton ?✓
Jack Mackerel Continuous Increase Nekton ✓ ✓
Pacic Chub Mackerel (age 0) Sporadic Increase Nekton ✓
Pacic Chub Mackerel Sporadic Increase Nekton ✓ ✓
Pacic Hake (age 0) Novel Increase Nekton ✓ ✓
Fisheries | www.sheries.org 471
Increased abundances of species such as the California
market squid, age- 0 Pacic Hake, age- 0 rocksh, and pyro-
somes were observed off the California coast before similar
changes occurred in our more northern survey region (Sakuma
etal. 2016; Brodeur etal., 2019). Warmwater anomalies rst
occurred in southern California coastal waters during spring
2014 and were subsequently detected farther north later in that
year (Gentemann etal. 2017). Similarly, northerly occurrences
of more southern species were observed rst in California and
then later to the north in our survey area.
Several studies in the NCC have reported very low abun-
dances of adult euphausiids during the past few years (Sakuma
et al. 2016; Peterson et al. 2017; Brodeur et al., 2019). In
strong contrast, we found an anomalously high biomass of
E.pacica furcilia larvae during our study in 2014–2016. In
addition, we counted but do not report on several other lar-
val stages of crustaceans in the same plankton samples. We
found that abundances of an earlier larval stage (calyptopis)
of E.pacica were also the highest ever observed during this
same time period, and larvae of another common euphausi-
id (Thysanoessa spinifera) as well as shrimp (Caridea) larvae
had similarly high abundance patterns during this time peri-
od (C.A.M., unpublished). Given the short larval duration
of E. pacica (20–35 d from hatching to early furcilia stag-
es; Bi etal. 2011), adult euphausiids must have been present
to release eggs in the NCC. Therefore, the presence of larval
euphausiids and the absence of adult euphausiids might have
been the result of adults moving to cooler waters, either deep-
er or farther offshore.
The extraordinary increase in age- 0 rocksh (4 SDs above
the mean) in our 2016 catches was a coastwide event, docu-
mented from California (McClatchie et al. 2016) to Alaskan
waters (Strasburger et al. 2018). This suggests that whatever
factors caused the increase in age- 0 rocksh operated over an
extremely large area. However, the juveniles of the more than
70 species of northeast Pacic rocksh are extremely difcult
to distinguish (Love etal. 2002); therefore, we could not doc-
ument which species were involved, and we did not attempt
to identify the mechanism(s) responsible for the increase.
Continued assessment of older, easier- to- identify rocksh
may provide more focus to our current observation.
Pyrosomes were extremely abundant in our 2017 catches,
while other gelatinous species returned to more typical abun-
dance levels (Figure2). In 2014, other surveys encountered
low numbers of pyrosomes further south of our study area as
well as offshore (Wells etal. 2017; Brodeur etal. 2018, 2019).
By 2015, the surveys captured pyrosomes at least as far north
as Willapa Bay, Washington, but well off the continental shelf.
Pyrosomes were also caught for the rst time, and in high
numbers, within Alaskan waters during the winter of 2016–
2017 and through summer 2017 (NOAA- AFSC 2017; Brodeur
etal. 2018). This dramatic expansion in range and abundance
clearly represents favorable conditions for pyrosomes and sug-
gests that their exceptionally high and widespread abundance
was not solely due to changes in water transport.
Consequences of Species Abundance Changes
Understanding the consequences of extreme changes in
species abundance in the NCC is challenging. Ruzicka et al.
(2012) explored changes in abundances of different trophic
groups in the NCC and used modeling to predict how these
changes would impact energy ows through the food web.
Many of the taxonomic groups they identied as important
nodes of energy ow (Figure3, boxes) are ones we found to
have undergone large increases (e.g., water jellysh, euphau-
siids, California market squid, Pacic Chub Mackerel, Jack
Figure3. Energy ow pathways between major functional groups in the Northern California Current food web (modied by J.
Ruzicka from Figure6a in Ruzicka etal. 2012). Box size is proportional to group production rates (whl=whales; msc=miscella-
neous; plgc=pelagic; mesoplgc=mesopelagic; bnthc=benthic; epibnthc=epibenthic; juv=juvenile; macro- Z=macrozooplank-
ton; micro- Z=microzooplankton; invrt=invertebrate; carn=carnivorous; susp=suspension- feeding; phyto=phytoplankton).
Red shading indicates species identied in this paper that have greatly increased or decreased during the recent marine heat
472 Fisheries | Vol. 44 • No. 10 • October 2019
Mackerel, and Pacic Hake) or decreases (e.g., Pacic sea net-
tles, juvenile Chinook Salmon, and juvenile Coho Salmon) in
abundance. However, our survey focused on the upper water
column during the day and did not sample all of the species
included in the food web analysis.
Decreased Pacic sea nettle abundance during 2015–2017
coincided with increased abundance of zooplankton prey spe-
cies. Sea nettles are known to feed on early stage euphausiids
(Suchman etal. 2008), so the decline in Pacic sea nettles may
have resulted in the high abundance of larval euphausiids in
2015 and 2016. The high juvenile rocksh abundance in 2016
may have been partly inuenced by the very low numbers of
Pacic sea nettles in 2015 due to both decreased predation on
larval rocksh in 2015 as well as decreased competition for
food between Pacic sea nettles and larval rocksh.
The sudden presence and extremely high abundance of
pyrosomes may be the best example of an ecosystem con-
sequence. Pyrosomes were not a component of the Ruzicka
etal. (2012) ecosystem analysis, as these organisms had never
been observed in the NCC (Welch 2017; Brodeur etal. 2018).
P. atlanticum was found to be an extremely effective grazer,
with clearance rates among the highest recorded for any
pelagic grazer (Perissinotto etal. 2007). The high abundance
of pyrosomes could explain the extremely low chlorophyll- a
concentrations we observed in 2017 and could have caused a
reduction in energy ow to higher trophic levels. If this organ-
ism remains abundant in subsequent years, it could produce
lasting effects upon the NCC ecosystem by outcompeting oth-
er lter feeders, which in turn might reduce the food supply to
organisms higher in the food web.
Finally, changes in abundance of various juvenile sh
species, including Pacic Hake, rocksh, Coho Salmon, and
Chinook Salmon, will affect top predators, such as sharks,
pinnipeds, toothed whales, and humans. We believe that the
increased abundances of age- 0 Pacic Hake and Pacic Chub
Mackerel in our 2016 samples were probably due to shifts in
adult spawning distribution (Auth etal. 2017) and thus may not
be indicative of increased abundances on a broad, regional scale.
If this is true, we do not expect the adult abundances of these
species to greatly increase in the future. In contrast, we think
that the very high abundance of juvenile rocksh in our 2016
samples and the very low abundances of yearling Coho and
Chinook Salmon in our 2017 samples represent real changes in
abundance that will likely affect adult recruitment. Low catches
of juvenile salmon in our June surveys have already been asso-
ciated with poor adult returns (Burke etal. 2013; Peterson etal.
2014), so we anticipate poor returns of Coho Salmon to the
Columbia River in 2018 and poor returns of Chinook Salmon
in 2019. The high abundance of juvenile rocksh in 2016 was
an extraordinary event, spanning at least 2,500km of coastline
along the west coast of North America. Although Ralston etal.
(2013) suggested that pelagic abundance of juvenile rocksh is
a good indicator of adult recruitment in central California, the
actual consequences of high juvenile rocksh abundance in
2016 remain to be seen in future years.
We have documented recent dramatic changes in abun-
dance of sh and invertebrates in the surface waters of the
NCC since 2014. These changes likely reect changes in phys-
ical processes and ecological mechanisms (Table2). Some of
what we observed was due to a shift of organisms from south
to north and from west to east, whereas other changes may be
the result of alterations in biological processes for organisms
that have not changed their distributions. It is notable that
we have not seen a complete changeover of species within the
NCC ecosystem—rather, we have seen the novel occurrence
of some organisms mixed with other species that are normally
present (Table2). Mixing of organisms from different regions
may result in novel trophic interactions with unpredictable re-
sults (Naiman et al. 2012). We are particularly interested in
potential continued ecological effects of the occurrence and
abundance of pyrosomes in the NCC during 2017 and beyond.
The value of this paper lies not only in the specic results
we described, but also in its role as a reminder of the impor-
tance of obtaining and maintaining long- term baselines to
measure biological change (McClatchie etal. 2014). We have
already described clear ecosystem- scale change in response
to large- scale climatic changes (the Blob and El Niño). The
National Marine Fisheries Service’s current emphasis on eco-
system management will only be successful if robust eld sur-
veys of those ecosystems continue (Levin etal. 2009).
We dedicate this paper in memory of Dr. Robert (Bob) L.
Emmett (1955–2015) and Dr. William (Bill) T. Peterson (1942–
2017), who conceived of this work, were amazing mentors and
dear friends, were lled with enthusiasm for life and science,
and inspired us as scientists and as human beings. We greatly
appreciate the many people who contributed to this project
over the years, including the captains and crews who operated
vessels, especially the FV Frosti, and the many scientists who
collected and processed samples. We especially thank Paul
Bentley, Cindy Bucher, Brian Burke, Ed Casillas, Elizabeth
Daly, Joe Fisher, Troy Guy, Susan Hinton, Kym Jacobson, Jesse
Lamb, Jim Ruzicka, and Jen Zamon. Funding for this study
was provided by the Bonneville Power Administration (Project
1998- 014- 00) and the National Oceanic and Atmospheric
Administration Fisheries. Constructive comments from Brian
Burke, Jennifer Fisher, Kym Jacobson, David Teel, and three
anonymous reviewers greatly improved the manuscript. There
is no conict of interest declared in this article.
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