ArticlePDF Available

Herring size-at-age variation in the North Pacific

Authors:

Figures

Hollowed, A.B., and Wooster, W.S. 1995.
Decadal-scale variations in the eastern
subarctic Pacific: II. Response of northeast
Pacific fish stocks. Can. Spec. Publ. Fish.
Aquat. Sci. 121: 373-385.
Mantua, N. J., Hare, S.R., Zhang, Y., Wallace,
J.M., and Francis, R.C. 1997. A Pacific
interdecadal climate oscillation with impacts
on salmon production. ,Bull. Am. Meteorol.
Soc. 78: 1069-1079.
Ware, D. M. 1992. Climate, predators and prey:
behaviour of a linked oscillating system. In
Kawasaki T., Tanaka S., Yoahiaki T., and
Taniguchi A. (eds). Long-term variability of
pelagic fish populations and their
environment. Pergamon Press, Sendai, Japan,
pp. 279-291.
Zebdi, A., and Collie, J. S. 1995. Effect of
climate on herring (Clupea pallasi) population
dynamics in the northeast Pacific Ocean. Can.
Spec. Publ. Fish. Aquat. Sci. 121: 277-290.
Herring size-at-age variation in the North Pacific
Jake Schweigert1, Fritz Funk2, Ken Oda and Tom Moore3
1 Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, BC, Canada. V9R 5K6 E-mail:
schweigertj@pac.dfo-mpo.gc.ca
2 Alaska Department of Fish and Game, P.O. Box 25526, Juneau, AK 99802-5526, U.S.A. E-mail:
fritz_funk@fishgame.state.ak.us
3 California Department of Fish and Game, Belmont and Bodega Bay, California, U.S.A.
Introduction
Herring have been one of the more important
components of the marine fisheries on the west
coast of North America over the past century.
Dramatic population fluctuations are common in
all stocks of herring but virtually all populations
from Alaska to California declined dramatically
and synchronously in the late 1960s and all have
subsequently recovered. Despite the impacts of a
significant harvest in most of these stocks, large
scale environmental forcing appears to have been
a significant factor in the observed population
fluctuations. However, it is unclear what
mechanisms were involved in affecting survival
over such a broad geographical scale. Long time
series of stock abundance estimates are not
available for most of these populations. Instead,
we investigated the available data on fish size and
growth, reviewing trends in weight-at-age,
condition factor, and growth increments of Pacific
herring from Alaska to California in relation to
environmental conditions or food supply to assess
whether these factors may have affected herring
survival in the North Pacific.
Methods
Pacific herring weight-at-age data were collated
for a number of stocks in the North Pacific (Fig.
30) ranging from the Bering Sea [Togiak] through
the Gulf of Alaska (Kodiak], Prince William
Sound [PWS]), SE Alaska [Sitka], British
Columbia (Queen Charlotte Islands [QCI], Prince
Rupert [PRD], Central Coast [CC], Strait of
Georgia [GS], west coast of Vancouver Island
[WCVI]), and California (San Francisco Bay
[SFB], Tomales Bay [TB]). Unfortunately, the
available data is sparse in many cases and
generally available for only limited time periods
restricting the type and extent of statistical
analyses possible. The time period investigated
for this study ranges from 1940-2000. For some
populations both length and weight at age data are
available and for those we examined changes in
condition factor. For all populations trends in
weight at age 4 were examined as well as trends in
the annual growth increment at age over time.
The condition factor was also calculated annually
for each age-class in each stock following Tesch
(1988), as:
3
at
at
tLength
Weight
CF =
47
Spratt (1987) has previously used similar methods
to examine growth variation in San Francisco Bay
herring following the strong 1982-83 El Niño.
The indices of environmental forcing that were
examined included the Pacific decadal oscillation
(PDO), atmospheric forcing index (AFI), the
Aleutian low pressure index (ALPI), the Pacific
circulation index (PCI) and the ENSO southern
oscillation index (SOI). All but the last index are
available from http://www.pac.dfo-mpo.gc.ca/sci/
sa-mfpd/english/clm_indx1.htm. The SOI index
was obtained from ftp://ftp.ncep.noaa.gov/pub/
cpc/wd52dg/data/indices/soi. Information on
plankton biomass is difficult to obtain since there
have been few long-term efforts to collect these
data. Recently, Hare and Mantua (2000) have
consolidated a large number of data series for the
period 1965-1997 and we have used their results
in this study.
Togiak Bay
Ko d ia k Pri nc e
William
Sound
Sitka
Queen
Charlotte
Islands
Pri nc e Rup e rt
Central
W. C . Va n c o u ve r Is .
Georgia
St ra i t
Berin g
Se a
Alaska
British
Columbia
California
Sa n Fra n c i sc o
Ba y
Tomales
Ba y
EBSZOO
CPZOO
EPZOO
CCZOO
Fig. 30 Map of the study area illustrating the
location of data sets for the analysis.
Results and discussion
Pacific herring generally exhibit a cline in size-at-
age from south to north, with fish in the Bering
Sea being far larger than fish from California.
Herring also mature at later ages as one progresses
from south to north. Therefore, comparison of
size, condition, and growth increment becomes
complicated as fish trade off growth for
reproduction once they are mature. Consequently,
we chose to examine trends in the average weight
of fish at age 4 throughout the study area
(Fig. 31). However, this is of limited utility as an
index of growing conditions because it represents
an integration by the fish of growing and feeding
conditions over the preceding four years. Fish
from the Bering Sea are much larger and
demonstrate greater fluctuation in size at age 4
than herring from any of the other areas. Sitka and
PWS indicate a long term decline in size since the
1940s. It should be noted that the pre-1970 data
from all areas represent fall reduction fisheries
whereas recent data are from spring roe fisheries
and so may reflect some loss of weight by fish
over the winter period. British Columbia stocks
and those from Sitka show a marked increase in
size at the time of the stock collapses in the early
1960s with a subsequent decline in the 1970s
which may reflect a density-dependent response
as the populations rebuilt. California stocks do
not show evidence of any trends except for
reductions in size during the 1982-83 and 1997-98
El Niño events.
The condition factor at age is presented in Figures
32 and 33. It represents an index of growing
conditions for herring the previous year.
However, it is possible that herring compensate
for reduced food availability by growing more
slowly in length while maintaining an average
condition. Thus, it may not be a good indicator of
growing conditions in the ocean except under
extreme circumstances such as a severe El Niño
which disrupted normal feeding patterns. British
Columbia herring stocks do not show any marked
trends in condition over time although the QCI,
CC, and WCVI suggest a slight increase in
condition from the 1950s through the 1990s.
48
1940 1950 1960 1970 1980 1990 2000
100 120 140 160 180 200
Weight at Age 4
100 120 140 160 180 200
TOGIAK
KODIAK
1940 1950 1960 1970 1980 1990 2000
60 80 100 120 140
Weight at Age 4
60 80 100 120 140
PWS
SITKA
1940 1950 1960 1970 1980 1990 2000
60 80 100 120 140
Weight at Age 4
60 80 100 120 140
QCI
PRD
CC
1940 1950 1960 1970 1980 1990 2000
60 80 100 120 140
Weight at Age 4
60 80 100 120 140
GS
WCVI
1940 1950 1960 1970 1980 1990 2000
60 80 100 120 140
Weight at Age 4
60 80 100 120 140
SF Bay
Tomales Bay
Fig. 31 Trends in weight-at-age 4 in Pacific herring from 1940-2000.
49
1940 1950 1960 1970 1980 1990 2000
1.1 1.3 1.5 1.7
1.1 1.3 1.5 1.7
Condition at Age
QCI
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
1.1 1.3 1.5 1.7
1.1 1.3 1.5 1.7
Condition at Age
PRD
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
1.1 1.3 1.5 1.7
1.1 1.3 1.5 1.7
Condition at Age
CC
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
1.1 1.3 1.5 1.7
1.1 1.3 1.5 1.7
Condition at Age
GS
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
1.1 1.3 1.5 1.7
1.1 1.3 1.5 1.7
Condition at Age
WC
Age 3
Age 4
Age 5
Age 6
Fig. 32 Condition factor at age for British Columbia herring from 1940-2000.
50
1940 1950 1960 1970 1980 1990 2000
1.1 1.3 1.5 1.7
1.1 1.3 1.5 1.7
Condition at Age
PWS
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
1.2 1.4 1.6 1.8
1.2 1.4 1.6 1.8
Condition at Age
SITKA
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
1.2 1.4 1.6 1.8
1.2 1.4 1.6 1.8
Condition at Age
SFB
Age 3
Age 4
Age 5
Age 6
1.2 1.4 1.6 1.8
1.2 1.4 1.6 1.8
Condition at Age
TB
Age 3
Age 4
Age 5
Age 6
Fig. 33 Condition factor at age for Alaska and California herring from 1940-2000.
51
1940 1950 1960 1970 1980 1990 2000
-50 0 50 100
-50 0 50 100
TOGIAK
Growth Inc at Age
Age 5
Age 6
Age 7
Age 8
1940 1950 1960 1970 1980 1990 2000
0204060
0204060
KODIAK
Growth Inc at Age
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
0204060
0204060
PWS
Growth Inc at Age
1940 1950 1960 1970 1980 1990 2000
-20 0 20 40 60
-20 0 20 40 60
SITKA
Growth Inc at Age
Fig. 34 Trends in the growth increment at age for Alaska herring stocks from 1940-2000.
1940 1950 1960 1970 1980 1990 2000
-20 0 20 40
-20 0 20 40
QCI
Growth Inc at Age
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
-20 0 20 40
-20 0 20 40
PRD
Growth Inc at Age
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
-20 0 20 40
-20 0 20 40
CC
Growth Inc at Age
Age 3
Age 4
Age 5
Age 6
Fig. 35 Trends in growth increment at age for northern BC herring stocks from 1940-2000.
53
1940 1950 1960 1970 1980 1990 2000
-20 0 20 40
-20 0 20 40
GS
Growth Inc at Age
Age 4
Age 5
Age 6
Age 7
1940 1950 1960 1970 1980 1990 2000
-20 0 20 40
-20 0 20 40
WCVI
Growth Inc at Age
Age 3
Age 4
Age 5
Age 6
1940 1950 1960 1970 1980 1990 2000
-20 0 20 40
-20 0 20 40
SFB
Growth Inc at Age
Age 2
Age 3
Age 4
Age 5
1940 1950 1960 1970 1980 1990 2000
-20 0 20 40
-20 0 20 40
TB
Growth Inc at Age
Age 3
Age 4
Age 5
Age 6
Fig. 36 Trends in the growth increment at age for southern BC and California herring stocks from
1940-2000.
54
1940 1950 1960 1970 1980 1990 2000
-3 -2 -1 0 1 2 3
Winter PDO
-3 -2 -1 0 1 2 3
1940 1950 1960 1970 1980 1990 2000
-3 -2 -1 0 1 2 3
AFI
-3 -2 -1 0 1 2 3
1940 1950 1960 1970 1980 1990 2000
-4-202468
ALPI
-4-202468
1940 1950 1960 1970 1980 1990 2000
-200 -100 0 100 200
PCI
-200 -100 0 100 200
1940 1950 1960 1970 1980 1990 2000
-2 -1 0 1 2
SOI
-2 -1 0 1 2
Fig. 37 Environmental indices for the North Pacific from 1940-2000.
55
All stocks also indicate a small decline in
condition in the mid- to late 1980s and again in the
late 1990s following the two strong ENSO events.
Results for Alaska and California are quite
variable with Sitka and PWS suggesting a marked
increase in condition from the 1940s through the
1960s although this may be a function of changes
in sampling locations. Both California stocks
suggest a very slight increase in condition factor
over time with sharp declines associated with the
1982-83 and 1997-98 ENSO events. Spratt (1987)
has previously reported the strong negative effects
of the 1982-83 El Niño on San Francisco Bay
herring condition factor and growth.
The growth increments at age for Pacific herring
stocks are presented in Figures 34-36 and are
perhaps the best indicator of growing conditions in
the previous year in each area. Togiak fish show
the largest growth increment coastwide which
includes a marked increase in the early 1990s
followed by a recent decline. PWS and Sitka
stocks do not demonstrate any long term trends in
growth increment although there are declines in
the mid-1980s and late 1990s which may
correspond to El Niño effects. British Columbia
stocks all show a decline in growth increment
from the early 1970s through the late 1990s. They
all show a marked decrease in 1997 and some in
the mid-1980s. The California stocks do not
indicate any clear trend in growth increment over
time but both show the effects of the 1982-83 El
Niño and SFB also the 1997-98 El Niño.
The environmental indices are presented in Figure
37 and demonstrate broadly similar patterns in
winter PDO, AFI, and ALPI based on a lowess
smoothed trend line. The PCI may be inversely
related to these indices but at a different frequency
since they are not quite in phase. The SOI index
appears to be inversely related to the first three
indices. A comparison of these indices with
herring weight at age 4, condition factor, and
growth increment does not indicate any strong
correlation but there is the suggestion of a loose
association between the trend in PDO and weight
at age 4, condition, and perhaps growth increment
since 1970.
Figure A9 from Hare and Mantua (2000) presents
the available zooplankton data for the North
Pacific and indicated a generally decreasing trend
in zooplankton biomass since the 1977 regime
shift (see Fig. A9 in their paper). This observation
is consistent with the observed declining trend in
herring growth increment in British Columbia but
surprisingly not in California. It is also consistent
with the trend of declining size at age 4 in British
Columbia and parts of Alaska. Although not
explicit in the plankton data, it is possible that
changes in species composition during El Niño
events are responsible for the marked decline in
growth observed during these time periods so that
overall plankton biomass remains relatively stable
but the preferred prey items for herring decline
markedly or are completely absent from the
normal feeding areas.
Pacific herring populations in the eastern Pacific
have experienced significant synchronous
fluctuations in abundance that appear to be related
to environmental forcing. We examined
biological characteristics associated with changes
in growth as a proxy for herring survival over the
available data record. Results indicate a complex
interaction between density dependent effects,
food supply, and environmental variation. During
the collapse of herring stocks throughout the
Pacific in the late 1960s growth of herring
increased dramatically, declining again as stock
rebuilt. During the period from 1977 to present
growth characteristics of many stocks in British
Columbia and Alaska have shown a decline which
is apparently a result of declining food availability.
Plankton availability is most probably driven by
changing environmental conditions that have at
least recently not been favourable for herring
growth in British Columbia and southern Alaska.
Superimposed on these relationships are the recent
strong ENSO episodes which have negatively
impacted herring growth through the area of their
effect. Overall, there appear to be threshold
effects related to population density, ocean
production and plankton availability, and sea
surface temperature mediated by ENSO that affect
the growth parameters of herring populations
throughout the North Pacific. Future studies
should be directed at defining the thresholds and
their effects on long-term herring production.
56
References
Hare, S.R., and Mantua, N.J. 2000. Empirical
evidence for North Pacific regime shifts in
1977 and 1989. Prog. Oceanography 47: 103-
145.
Spratt, J.D. 1987. Variation in the growth rate of
Pacific herring from San Francisco Bay,
California. Calif. Fish and Game 73: 132-138.
Tesch, F.W. 1988. Age and Growth. In W.E.
Ricker [ed.] Methods of assessment of fish
production in fresh waters’. IBP Handbook
No. 3. Blackwell Scientific Publications,
Oxford, pp. 93-123.
Implications of variation in euphausiid productivity for the growth,
production and resilience of Pacific herring (Clupea pallasi) from the
southwest coast of Vancouver Island
Ron W. Tanasichuk
Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, B.C. Canada. V9R 5K6. E-mail:
tanasichukr@pac.dfo-mpo.gc.ca
This presentation includes the results of a number
of studies which collectively suggest that the
recent order of magnitude reduction in euphausiid
production along the southwest coast of
Vancouver Island depressed the productivity and
resilience of the West Coast Vancouver Island
(WCVI) herring (Clupea pallasi) population.
We have been studying the oceanography of the
southwest coast of Vancouver Island since 1985 to
learn how the ocean affects fish productivity there.
Results of diet analyses show that euphausiids are
the dominant prey of the more abundant pelagic
fish species and that herring feed on them
exclusively. We have also been monitoring the
species and size composition of prey. Tanasichuk
(1999) showed that Pacific hake (Merluccius
productus), the dominant planktivore, selects
larger (>17 mm) euphausiids of one species
(Thysanoessa spinifera) regardless of how
euphausiid biomass varies. WCVI herring select
the same prey. Euphausiid population biology and
productivity along the WCVI have been monitored
since 1991 (Tanasichuk 1998). Figure 38 shows
that herring and hake prey biomass has varied by
an order of magnitude over the last 10 years. The
same degree of prey variation has also occurred
for coho salmon (Oncorhynchus kisutch).
The effect on herring productivity and resilience
appears to operate through influencing growth.
Tanasichuk (1997) examined the effect of
variations in year-class strength and
oceanographic conditions on the size of recruit
herring and the growth rates of adult fish. At that
time, data were available to 1996 only. He
suggested that the 1993 year-class was an outlier
because this year-class was the first to be
subjected to low T. spinifera biomass over its first
three years of life. All subsequent year-classes
have been outliers, over a period when T. spinifera
biomass remained depressed (Fig. 39). This
dataset suggests that the compensatory population-
0
100
200
300
400
0
1000
2000
3000
Year
1991 1992 1993 1994 1995 1996 19981997 1999 2000
>17 mm
9-12 mm
Median T. spinifera biomass (mg dry mass.mg -2 )
Fig. 38 Median biomass (mg dry mass/mg2) of
key prey for Pacific herring and Pacific hake (>17
mm T. spinifera) and coho salmon (9-12 mm T.
spinifera) over the summer feeding period.
57
... There were large, uncontrolled commercial fisheries on Prince William Sound (PWS) herring from 1904 until 1967 (Brown and Carls 1998) until the population size became reduced. During the 1960's, there were parallel herring population declines throughout the North Pacific (Schweigert 2002, Brown 2002. Monitoring of herring biomass in PWS began in the early 1970's, at which time the estimated biomass was about 30 metric tons . ...
... Clupeids, including Pacific herring, typically have "boom or bust" population cycles, even in unstressed populations (Schweigert 2002). Before the oil spill, strong year classes historically dominated the PWS spawning populations about every four years and the spawning population was dominated by the 1984 year class at the time of the spill (Brown and Carls 1998;. ...
... Hay et al. (2001) report the 2000 spawning biomass to be about 25,000 metric tons. Given Schweigert's (2002) weight of 100 g for age 4 herring from San Francisco Bay, this biomass corresponds to 250 million fish and a N e /N ratio of 3 x 10 -4 to 1.5 x 10 -6 . The N e /N ratio for San Francisco Bay is similar to that of PWS. ...
... WCVI, West Coast Vancouver Island; PWS, Prince William Sound; BS, Bering Sea. rates of ages 3–5 for comparative analyses (e.g., Schweigert et al., 2002 ). In order to detect shifts in the monthly temperature and zooplankton densities, we computed annual values of each. ...
... We also tried to compare our predicted herring responses to general responses of fish reported for each of the three regions. Long-term records of herring weights-at-age exist for PWS and WCVI (Schweigert et al., 2002). Given the time periods of the predicted shifts in growth rates and the availability of weights-at-age data, two direct comparisons were possible . ...
... –1989;Fig. 7a ) agreed with the lower average weight at age-4 observed in the field data for the same time periods (88.5 g versus 96.4 g). Additional direct model to data comparisons are difficult because of the time gaps in the observed weights-at-age data. Previous studies have also analyzed the long-term observed weights-at-age data for herring. Schweigert et al. (2002) analyzed weights-at-age data for 11 herring populations , including WCVI, PWS, and BS, and suggested that annual growth rates seemed to respond to ENSO events, with warmer waters having a negative effect on growth. He also suggested that herring growth has generally decreased since 1977 in many British Columbia and Alaska stocks, which ...
Article
The infrequent occurrence of climate regime shifts and the long-lived life history of many harvested fish species imply that quantitative understanding of the effects of climate shifts on fish will require long-term data spanning decades. We use the output of the 3-dimensional (3D) NEMURO nutrient–phytoplankton–zooplankton model applied to the Northern Pacific as input to a Pacific herring (Clupea pallasi) bioenergetics model, and predict herring weights-at-age and growth from 1948 to 2000 for the West Coast Vancouver Island (WCVI), Prince William Sound (PWS), and Bering Sea (BS) locations. The feeding parameters of the bioenergetics model were calibrated from steady-state predictions of herring weights-at-age at each location compared to observed mean weights-at-age. Herring weights-at-age were then simulated from 1948 to 2000 using the 3D-NEMURO generated time series of monthly temperature and zooplankton densities. Herring growth rates, annual temperature, and zooplankton density time series were analyzed statistically for coincident shifts in their mean values. We also simulated herring growth rates using the 1948–2000 time series and averaged (climatological) temperature and zooplankton densities to determine the relative importance of temperature and zooplankton to predicted herring growth responses. All three locations showed a shift in herring growth during the mid and late 1970s. Herring growth decreased in WCVI and PWS, and increased in BS; these changes were coincident with a warming of temperature and a decrease in predatory zooplankton density. Herring growth responses in PWS and BS were more complex than those predicted for WCVI, with additional shifts predicted besides the late 1970s shift. Interannual variation in zooplankton densities caused the herring growth response for WCVI. Temperature and zooplankton densities affected the herring growth responses in both Alaskan locations, with zooplankton dominating the response for PWS and temperature dominating the response for BS. We compare our simulated herring growth responses to observed responses, and discuss the advantages and drawbacks of using the output of broadly applied lower trophic model as input to fish models in order to examine long-term responses to regime shifts at multiple locations.
... As a result, herring growth (Fig. 4) in the eastern North Pacific, which was revealed as the first princi-704 pal component (Fig. 4). 705 The simulated growth increase in the middle of 1980s for WCVI 706 agreed with observations in the field data (Schweigert et al., 2002). 707 Similarly, the slow growth rate period predicted in PWS for 1992-708 1997 agreed with the lower average weight at age-4 observed in 709 the field data for the same time periods (88.5 g versus 96.4 g; 710 Schweigert et al., 2002). ...
... 705 The simulated growth increase in the middle of 1980s for WCVI 706 agreed with observations in the field data (Schweigert et al., 2002). 707 Similarly, the slow growth rate period predicted in PWS for 1992-708 1997 agreed with the lower average weight at age-4 observed in 709 the field data for the same time periods (88.5 g versus 96.4 g; 710 Schweigert et al., 2002). Unfortunately, comparable data for the 711 western North Pacific were not available. ...
... Similar patterns were seen in the Gulf of Alaska with higher productivity during positive phases of the Pacific Decadal Oscillation (warmer nearshore conditions) from 1902 to 1995 (Brown, 2002). However, some stocks show declines in production during El Niño events and the years of regime shifts depending on location (Mantua, 1997;Schweigert et al., 2002;Ito et al., 2015). Togiak herring, a stock from Bristol Bay in the eastern Bering Sea, showed increases in growth rates with warming, while southern stocks showed decreases in growth rates with warming (Ito et al., 2015). ...
Article
Full-text available
Climate change is altering the distribution and biomass of marine species in Arctic and sub-Arctic waters. In this study, we investigate the influence of sea temperature on the annual distribution and biomass of pelagic fishes in the eastern Bering Sea during late summer, 2002-2018. The distribution (easting, northing, and area occupied) and biomass of capelin, Pacific herring, juvenile chum salmon, juvenile pink salmon, juvenile sockeye salmon, and age-0 walleye pollock collected by surface trawl were estimated using a standardized geostatistical delta-generalized linear mixed modeling approach. Species showed varied responses to warming on a temporal scale. Warming corresponded with more northerly distributions for capelin and juvenile sockeye salmon, a more westerly distribution of juvenile sockeye salmon, and range expansions for juvenile chum and sockeye salmon. Warming corresponded to a decrease in the annual biomass of capelin and an increase in the biomass of herring, age-0 pollock, and juvenile sockeye salmon. The spatio-temporal covariation in sea temperature and the distribution was nonlinear for juvenile pink salmon and age-0 pollock, positive for juvenile chum salmon and juvenile pink salmon, and negative for capelin indicating different responses of the distribution of pelagic fishes to warming in the eastern Bering Sea during late summer. In warmer areas, we found that the catch rates were higher for juvenile pink salmon, lower for capelin, and not significantly different for juvenile chum salmon, herring, age-0 pollock, and juvenile sockeye salmon. Juvenile sockeye salmon, a southerly distributed species in the survey area, appeared most responsive to warming. In this study, sockeye salmon and pollock are the most commercially important species while chum salmon are important for subsistence fishing. These temperature related changes during early life history stages for survival may have impacts on the numbers of these fishes recruiting to the fisheries.
... Declining weight-at-age is observed in all five of the major stocks, and despite area closures over the last 10-years, has continued to occur in the HG and WCVI stocks. This trend has been observed in B.C. and U.S. waters, from California to Alaska (Schweigert et al. 2002), however the direct cause and influence of this decline should be investigated in the context of the assessment framework. ...
Technical Report
Full-text available
This document presents stock assessments for Pacific Herring (Clupea pallasii) in British Columbia waters using data current to 2013. Results of the work are intended to serve as advice over the short term to fishery managers and stakeholders on current stock status and likely impacts of different harvest options. As in previous work, an integrated combined-sex statistical catch-at-age model (ISCAM) was applied independently to each of seven stock areas and tuned to fishery-independent spawn index data, annual estimates of commercial catch since 1951, and age composition data from the commercial fishery and from the test fishery charter program. Assessments were done for five major stock areas: Haida Gwaii (HG), Prince Rupert District (PRD), Central Coast (CC), Strait of Georgia (SOG), and West Coast of Vancouver Island (WCVI), and two minor herring stock management areas: Haida Gwaii Area 2W, and WCVI Area 27. Results are summarized as stock reconstructions, status of spawning stock in 2013, and projected spawning biomass in 2014. The model estimated stock-recruitment parameters, time-varying natural mortality, catchability coefficients for the survey time series, and selectivity parameters for the commercial fishery and those survey series for which age data are available. Estimates of unfished equilibrium spawning biomass (SB0) arose from Beverton-Holt stock-recruitment relationships (within the assessment model), calculated using average trends in weight-at-age, natural mortality and recruitment. All calculations were made using the Bayesian Markov Chain Monte Carlo (MCMC) method to quantify the uncertainty associated with parameter estimation. Estimates of various quantities were calculated from these samples, and are presented as the 5 and 95% credible quantiles, with median values in parentheses. Calculated probabilities are based on joint posterior distributions. One-year spawning biomass projections for 2014 were performed for each major and minor stock area over a range of constant catches to estimate probabilities that spawning biomass and harvest rate metrics are below and above control points historically used in the management of Pacific Herring, as specified in the herring harvest control rule. The assessment shows current status of major stocks to have increased in 2013 over 2012 and the 2013 median posterior spawning biomass (SB2013) is estimated to be a greater proportion of estimated unfished equilibrium level (SB0) compared to previous years. Ratio estimates (and 90% credibility intervals) of SB2013 / SB0 by major stock area are as follows: HG = 0.80 (0.42-1.49); PRD = 0.49 (0.25-0.90); CC = 0.48 (0.29-0.78); SOG = 0.97 (0.62-1.48), and WCVI= 0.40 (0.23-0.66). For HG, CC and WCVI stocks, where there have been no commercial removals in recent years, the model predicted increases in spawning biomass and recruitment, and decreases in natural mortality in order to explain observed increases in herring spawn index. Common observations across all five major herring stocks include: increases in the spawn index and spawning biomass, most significantly for HG, SOG and CC; declining weight-at-age from mid-1980s to 2010, and apparent decreases in the instantaneous natural mortality rate. For the minor areas, the assessment shows that Area 2W spawning stock biomass has been decreasing since 2011, driven by a declining spawn index since 2010 and apparent increases in the instantaneous natural mortality. For Area 27, the assessment shows that the spawning stock biomass has been at a constant level over the past 10-years but instantaneous natural mortality has been decreasing. Ratio estimates (and 90% credibility intervals) of SB2013 / SB0 by minor stock area are: Area 2W =1.10 (0.45-2.33) and Area 27 = 0.55 (0.31-0.98). Uncertainty associated with truncated catch data (1972 – present) and an adjustment in the spawn index to account for lead-line changes (2003-2013) was explored through sensitivity runs of the major areas. Fitting the model to a truncated time series had varying effects between stock areas whereas adjustments to spawn widths had negligible influence on model output.
... Over the past 3 decades, older individuals have become less numerous in British Columbian and Washington stocks (Landis & Bryant 2010), average weight-at-age has declined by as much as ca. 25% for spawners in some stocks (Schweigert et al. 2002), and the temporal window over which spawning occurs has narrowed (Therriault et al. 2009). These observations indicate that climate sensitivity may have increased over time for Pacific herring but requires further study. ...
Article
Full-text available
We examined how local-and regional-scale environmental drivers affect patterns of abundance and recruitment in 2 abundant and ecologically significant forage fishes (Pacific herring Clupea pallasi and surf smelt Hypomesus pretiosus) in the Skagit River estuary (Puget Sound, Washington, USA). We identified associations between survey catch rates and environmental conditions at 2 scales: within-season distributional shifts in response to local environmental conditions, and inter-annual patterns of relative year class strength related to both local-and regional-scale drivers. Using monthly data that spanned a 9 yr period, we found that a small proportion (< 2%) of the total deviance in catch rates for both species was related to within-estuary variation in surface water temperature and salinity but that a larger fraction (7 and 12% for Pacific herring and surf smelt, respectively) was explained by interannual variation in recruitment strength. Annual abundance indices for both species were uncorrelated with cumulative river discharge and regional sea surface temperature but positively correlated with an index of cumulative coastal upwelling, suggesting a linkage between regional-scale environmental conditions and age-0 recruitment. Moreover, our annual age-0 Pacific herring time series was positively correlated with a similar time series from the Strait of Georgia (similar to 100 km north), further suggesting that age-0 recruitment in these populations is synchronized by regional upwelling as opposed to estuary-specific environmental forcing related to river flows. The present study isolates a potential key process governing age-0 forage fish abundance in this system and highlights the importance of simultaneously evaluating patterns of variability across multiple spatiotemporal scales in order to identify the primary pathways through which climate may impact estuarine populations.
... Over the past 3 decades, older individuals have become less numerous in British Columbian and Washington stocks (Landis & Bryant 2010), average weight-at-age has declined by as much as ca. 25% for spawners in some stocks (Schweigert et al. 2002), and the temporal window over which spawning occurs has narrowed (Therriault et al. 2009). These observations indicate that climate sensitivity may have increased over time for Pacific herring but requires further study. ...
Article
Full-text available
We examined how local- and regional-scale environmental drivers affect patterns of abundance and recruitment in 2 abundant and ecologically significant forage fishes (Pacific herring Clupea pallasi and surf smelt Hypomesus pretiosus) in the Skagit River estuary (Puget Sound, Washington, USA). We identified associations between survey catch rates and environmental conditions at 2 scales: within-season distributional shifts in response to local environmental conditions, and interannual patterns of relative year class strength related to both local- and regional-scale drivers. Using monthly data that spanned a 9 yr period, we found that a small proportion (<2%) of the total deviance in catch rates for both species was related to within-estuary variation in surface water temperature and salinity but that a larger fraction (7 and 12% for Pacific herring and surf smelt, respectively) was explained by interannual variation in recruitment strength. Annual abundance indices for both species were uncorrelated with cumulative river discharge and regional sea surface temperature but positively correlated with an index of cumulative coastal upwelling, suggesting a linkage between regional-scale environmental conditions and age-0 recruitment. Moreover, our annual age-0 Pacific herring time series was positively correlated with a similar time series from the Strait of Georgia (~100 km north), further suggesting that age-0 recruitment in these populations is synchronized by regional upwelling as opposed to estuary-specific environmental forcing related to river flows. The present study isolates a potential key process governing age-0 forage fish abundance in this system and highlights the importance of simultaneously evaluating patterns of variability across multiple spatiotemporal scales in order to identify the primary pathways through which climate may impact estuarine populations.
... When we compare the mean SP t /B t (production per biomass) vs. B t relationship for the reduction fishery with later years , all stocks have clearly shown a decrease in mean productivity at both low and high stock sizes. This decrease is explained at least partly by decreases in mean body weight at age (Tanasichuk 1997;Schweigert et al. 2002), but may also be related to loss of spatial stock structure; some spawning areas are no longer used (D. Hay, Fisheries and Oceans Canada, Pacific Biological Station, Hammond Bay Road, Nanaimo, British Columbia, Canada, personal communication). ...
Article
Surplus production rates predicted by simple biomass dynamics models are generally expected to follow a simple dome-shaped pattern as population size changes and to show similar trajectories during population decline and recovery. Age-structured models, however, predict substantially lower surplus production rates during population recovery than during decline because of reduced mean fecundity, unless recruitment compensation is very strong. Ecosystem models like Ecosim predict more complex patterns, with reduced production during recoveries due to both age-structure effects and cultivation-depensation effects related to changes in competitor and predator abundances. Production-driven recoveries, where surplus production per biomass is higher during recovery than decline, are predicted in cases where there has been substantial change in overall ecosystem productivity or community structure. 110 case examples illustrate that simple, repeatable relationships between stock size and production are uncommon, and the most common pattern is production-driven change in stock size, where changes in production rate apparently independent of stock size then drive stock increase or decrease. We conclude that nonstationarity in productivity needs to be considered as part of population rebuilding and that empirical estimates of surplus production may provide insight in this process.
... They concluded that these groupings reflected temporal synchrony and suggested that largescale oceanographic phenomena have a large influence. Schweigert et al. (2002) examined the mean weight at age of 4-year-olds and the condition factor and annual growth increments of 3-to 6-year-old herring for about 10 eastern North Pacific herring stocks for 1940-2000. They found the expected latitudinal patterns (e.g., older age of maturation in the north), instances of synchrony in growth among some but not all populations, and weak but suggestive correlations of growth with ocean climate indices such as the Pacific Decadal Oscillation. ...
Article
Full-text available
We used a nutrient-phytoplankton-zooplankton (NPZ) model coupled to a fish bioenergetics model to simulate the weight-at-age responses of Pacific herring Clupea pallasii to climate regimes. The NPZ model represents the daily dynamics of the lower trophic levels by simulating the uptake and recycling dynamics of nitrogen and silicon and the photosynthesis and grazing interactions of multiple functional groups of phytoplankton and zooplankton. The bioenergetics model simulates the number and mean weight of Pacific herring for each of 10 age-classes. Three zooplankton groups simulated in the NPZ model provide estimates of the prey used to determine the consumption component of the herring bioenergetics model. We used a spawner-recruit relationship to estimate the number of new age-1 individuals joining the herring population every year. The coupled models were applied to the coastal upwelling area off the west coast of Vancouver Island. Model simulations were performed to isolate the effects of each of four documented climate regimes on Pacific herring weights at age. The climate regimes differed in the environmental variables used in the spawner-recruit relationship as well as in the water temperature, mixed-layer depth, and nutrient influxing rate used by the NPZ model. In agreement with general opinion and with the Pacific herring data from the west coast of Vancouver Island, the model-predicted estimates of weight at age, recruitment, and spawning stock biomass were highest in regime 1 (1962-1976), intermediate in regime 2 (1977-1988), and lowest in regime 3 (1989-1999). Insufficient time has passed to adequately document the conditions and herring responses in regime 4 (1998-2002). The overall regime effect on weights at age was a mix of recruitment effects and lower trophic level effects that varied in direction and magnitude among the four regimes. Coupling bioenergetics models to physics and food web models is the next challenge in understanding and forecasting how climate change will affect fish growth and population dynamics.
Article
Timing of reproduction may be of crucial importance for fitness, particularly in environments that vary seasonally in food availability or predation risk. However, for animals with spatially separated feeding and breeding habitats, optimal reproductive timing may differ between parents and their offspring, leading to parent-offspring conflict. We assume that offspring have highest survival and fitness if they are spawned around a fixed date, and use state-dependent life-history theory to explore whether variation in conditions affecting only parents (food availability and survival) may influence optimal timing of reproduction. We apply the model to Pacific herring (Clupea palasii) in Puget Sound, USA, where 20 subpopulations spawn at different times of the year. Our model suggests that relatively small differences in adult food availability can lead to altered prioritization in the trade-off between maternal fecundity and what from the offspring’s perspective is the best time to be spawned. Our model also shows that observed among-population variability in reproductive timing may result from adults using different feeding grounds with divergent food dynamics, or from individual variation in condition caused by stochasticity at a single feeding ground. Identifying drivers of reproductive timing may improve predictions of recruitment, population dynamics, and responses to environmental change.
Article
Full-text available
It is now widely accepted that a climatic regime shift transpired in the North Pacific Ocean in the winter of 1976–77. This regime shift has had far reaching consequences for the large marine ecosystems of the North Pacific. Despite the strength and scope of the changes initiated by the shift, it was 10–15 years before it was fully recognized. Subsequent research has suggested that this event was not unique in the historical record but merely the latest in a succession of climatic regime shifts. In this study, we assembled 100 environmental time series, 31 climatic and 69 biological, to determine if there is evidence for common regime signals in the 1965–1997 period of record. Our analysis reproduces previously documented features of the 1977 regime shift, and identifies a further shift in 1989 in some components of the North Pacific ecosystem. The 1989 changes were neither as pervasive as the 1977 changes nor did they signal a simple return to pre-1977 conditions. A notable feature of the 1989 regime shift is the relative clarity that is found in biological records, which contrasts with the relative lack of clear changes expressed by indices of Pacific climate. Thus, the large marine ecosystems of the North Pacific and Bering Sea appear to filter climate variability strongly, and respond nonlinearly to environmental forcing. We conclude that monitoring North Pacific and Bering Sea ecosystems may allow for an earlier identification of regime shifts than is possible from monitoring climate data alone.
Variation in the growth rate of Pacific herring from San Francisco Bay
  • J D Spratt
Spratt, J.D. 1987. Variation in the growth rate of Pacific herring from San Francisco Bay, California. Calif. Fish and Game 73: 132-138.
Age and Growth Methods of assessment of fish production in fresh waters'. IBP Handbook No. 3
  • F W Tesch
Tesch, F.W. 1988. Age and Growth. In W.E. Ricker [ed.] Methods of assessment of fish production in fresh waters'. IBP Handbook No. 3. Blackwell Scientific Publications, Oxford, pp. 93-123.