October 17, 09:10 (W2-9710)
Pacific salmon and steelhead: Life in a changing winter ocean
Katherine W. Myers1, James R. Irvine2, Elizabeth A. Logerwell3, Shigehiko Urawa4, Svetlana V.
Naydenko5, Alexander V. Zavolokin5 and Nancy D. Davis6
1
School of Aquatic & Fishery Sciences, University of Washington (Retired), Seattle, WA, USA
E-mail: kwmyers@uw.edu
2
Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, Canada
3
NOAA Alaska Fisheries Science Center, Seattle, WA, USA
4
Salmon Resources Division, Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Sapporo,
Japan
5
Pacific Scientific Research Fisheries Centre (TINRO-Centre), Vladivostok, Russia
6
North Pacific Anadromous Fish Commission, Vancouver, BC, Canada
How Pacific salmon and steelhead (Oncorhynchus spp.) respond to seasonal and interannual changes in
their marine environment is highly uncertain, in part due to limited information on ocean life history and
ecology, especially during winter. We provide an overview of what is known and needs to be known
about winter ocean life history and ecology of Oncorhynchus to address the central question of this
workshop: Where do Pacific salmon go in the winter and why, and how might this be affected by climate
change? Historical research programs (1950s-1980s) established the ‘stock concept’ of oceanic
distribution of Oncorhynchus, determined the dominant oceanographic features (currents, water masses,
temperature-salinity) in regions where Oncorhynchus migrate, and discovered that Oncorhynchus exhibit
broad seasonal (north-south) movements, with most Bering Sea salmon overwintering in areas south of
the Aleutian Islands chain during winter. In recent decades (1990s-2010s), new fisheries-oceanographic
survey methods, stock-identification techniques, remote sensing technologies, and analytical methods
have expanded understanding of winter ecology of Oncorhynchus, although empirical data are still very
limited. In general, we learned that the “why” of ocean distribution of Oncorhynchus is complex and
variable, depending on spatiotemporal scale and synergies among heredity, environment, population
dynamics (abundance and density-dependence), and phenotypic plasticity (ability of an individual fish to
alter its biochemisry, physiology, behavior, and life history in response to environmental stimuli and
cues). The development of quantitative multispecies, multistage models of ocean distribution of
Oncorhynchus would help to identify key factors influencing winter distribution and improve
understanding of potential climate change effects.
October 17, 09:40 (W2-9495)
Temporal and spatial variation in growth factors of Pacific Salmon
Hiromichi Ueno1, Moeko Otani1, Maki Noguchi Aita2, Michio J. Kishi1 and Masahide
Kaeriyama1
1
Hokkaido University, Sapporo, Japan. E-mail: ueno@fish.hokudai.ac.jp
2
JAMSTEC, Yokohama, Japan
Pacific salmon occupy an important role as a keystone species in the North Pacific ecosystem.
The abundance and survival of Pacific salmon vary at inter-annual to inter-decadal time-scales.
They are related to variations in the physical environment of the North Pacific, especially sea
surface temperature (SST), and many studies relate dominant patterns of SST variability in the
North Pacific with Pacific salmon production. However, ecosystems in the subarctic North
Pacific are also affected by more detailed oceanographic structures, e.g. mesoscale eddies,
haloclines, temperature inversions, etc. This talk will discuss the physical environment in the
subarctic North Pacific including these oceanographic structures especially in winter. We also
investigate temporal and spatial variation in growth factors (temperature-dependence function
and prey-density function for consumption) of Pacific salmon from the view point of
bioenergetics. Zooplankton density obtained NEMURO embedded in a 3-D physical model is
used for prey density and Empirical Orthogonal Function (EOF) analysis is conducted in the
subarctic North Pacific. The first EOF mode for the prey-density function is related to the Pacific
Decadal Oscillation.
October 17, 10:10 (W2-9439)
Is winter a critical period for Pacific salmon? A critical review of the “critical-period”
hypothesis
Marc Trudel1,2 and Jim Irvine1
1
Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, BC, Canada
E-mail: marc.trudel@dfo-mpo.gc.ca
2
Department of Biology, University of Victoria, Victoria, BC, Canada
In a seminal paper published one hundred years ago, Hjort hypothesized that for Norwegian
herring and cod stocks, year-class strength, defined as the abundance of a given cohort, was
determined during a critical period very early in the fishes’ life history. More recently, Beamish
and Mahnken applied the critical period concept to Pacific salmon, proposing two marine critical
periods: an early predation-based mortality that occurs during the first few weeks following
ocean entry, and a starvation-based mortality period during the first fall and winter at sea.
Because the susceptibility to predation and starvation is generally affected by size in fish, they
further hypothesized that size-dependent mortality would be apparent in Pacific salmon during
these critical periods. In this presentation, we review the research conducted on overwinter
mortality of Pacific salmon during their first year at sea. Our review shows there is mounting
evidence that overwinter mortality is size-selective in juvenile Pacific salmon. However, there is
little evidence to date that year class strength is regulated by overwinter mortality for Pacific
salmon. Further tests of the critical period hypothesis will require direct estimation of overwinter
mortality over at least several years.
October 17, 10:50 (W2-9496)
Russian research on winter dwelling of Pacific salmon in the central and western parts of
the Subarctic Front zone
Svetlana V. Naydenko
Pacific Scientific Research Fisheries Centre TINRO-Centre, Vladivostok, Russia
E-mail: naydenko@tinro.ru
Offshore waters of the North Pacific are the main ocean habitat of Pacific salmon during winter
and spring periods. To understand the factors that influence survival of salmon during winter and
spring in the open ocean, Russian research was conducted from 1986 to 1992 and in 2009, 2010
and 2011. It was established that the distribution of pink salmon and chum salmon is determined
by the shape of the landscape zone favorable for their dwelling in winter-spring, which depends
on the mode of the western Subarctic gyre in the Northwest Pacific, on the mode of the Subarctic
Front, and on the intensity of the ocean branches of the East-Kamchatka Current and the
Aleutian Current. In addition, the quantitative parameters of pink salmon distribution depend on
fluctuations in its abundance between odd and even years. The results of plankton, nekton and
trophological investigations indicate that there are sufficient forage reserves for salmon in the
open ocean in winter and spring periods and that there is a lack of rigid limitation of salmon
abundance by food. Analysis of the dynamics of the biochemical characteristics of juvenile
Pacific salmon muscle tissue during autumn migrations to the Sea of Okhotsk and winter
migrations to the northwestern part of the Pacific Ocean was done. As a result information about
seasonal energetic reversions in the organism of juvenile Pacific salmon and about their strategic
behavioral and biochemical adaptations in the course of the first year of life in the ocean was
obtained.
October 17, 11:10 (W2-9529)
Distribution of Pacific salmon in the North Pacific Ocean & adjacent seas, with particular
emphasis on winter
David W. Welch1, Yukimasa Ishida2, Kazuya Nagasawa3 and Sonia D. Batten4
1
Kintama Research Services, Nanaimo, BC, Canada. E-mail: david.welch@kintama.com
National Research Institute of Far Seas Fisheries, Shimizu, Shizuoka, Japan
3
School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan
4
Sir Alister Hardy Foundation for Ocean Science, Plymouth, UK
2
The marine behaviour of Pacific salmon is poorly understood. Several publications in the last
two decades have examined the thermal limits of salmon in the offshore. In this presentation we
re-visit the complete 40 year dataset compiled by Welch et al. covering the period 1956-1996
(N=20,397 sampling locations). Plots of abundance show that the six species have different
geographic distributions within the North Pacific and that the locations where they are found
change seasonally. Although data for the winter period are limited, all species show a sharp
upper (southern) thermal limit on the offshore marine distribution, with sockeye the most
coldwater species and steelhead and coho the most warmwater species. The critical temperatures
defining the southern (warmer) limit to the salmon distribution vary by species and by season,
with acceptable temperatures increasing into the summer and becoming more similar between
species.
Recent IPCC projections of the amount of future warming are similar to those predicted two
decades ago using simpler steady state models. For several species the available data indicate a
near-complete loss of thermally acceptable salmon habitat in major areas of the North Pacific
Ocean. The projected impacts of global warming in the ocean could thus jeopardize the billions
of dollars national governments invested in salmon restoration efforts and suggest that explicit
testing of these apparent thermal limits is called for. A carefully designed tagging study using
archival tags could potentially provide the data needed for these tests, but will require that high
technical standards are met.
October 17, 11:30 (W2-9599)
Distribution and trophic conditions of chum and pink salmon in the North Pacific Ocean
during winter under climate change
Shigehiko Urawa1, Toshiki Kaga2, Tomonori Azumaya2, Shunpei Sato1, Masa-aki Fukuwaka3
and Terry Beacham4
1
Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Sapporo, Japan
E-mail: urawa@affrc.go.jp
2
Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Kushiro, Japan
3
Seikai National Fisheries Research Institute, Fisheries Research Agency, Nagasaki, Japan
4
Pacific Biological Station, Fisheries & Oceans Canada, Nanaimo, BC, Canada
Winter is believed to be a crucial period for salmon survival in the ocean, but few biological data
exist to support this hypothesis. The present paper aims to estimate stock- or age-specific
distribution and trophic condition of winter chum and pink salmon and assess the impacts of
climate change on their distribution and survival. Fish were caught with a surface trawl on the
Japanese R/V Kaiyo-maru in the North Pacific Ocean (NPO) and Bering Sea during winter of
1996, 1998 and 2006. Young (ocean age-1) chum and pink salmon were abundant in the western
NPO, while older chum salmon were mainly distributed in the Gulf of Alaska (GOA). Genetic
stock identification confirmed various chum salmon stocks of Asian and North American origins
intermingled in the GOA. North American stocks were dominant in the northern GOA, and
Asian stocks were dominant in the southern GOA. Mean SST of winter chum salmon habitats
was almost stable among years but differed between regions: around 4ºC in the western NPO and
6ºC in the GOA. Ocean age-1 chum salmon had lower lipid content than older fish, suggesting a
critical condition of young fish during their first winter. The total lipid content of chum and pink
salmon was significantly lower in the GOA than in the western NPO, perhaps due to higher
habitat temperature and/or low availability of prey organisms. Two climate warming scenarios
(SST increase of 1.5ºC or 3ºC) have suggested the winter habitat space for chum salmon will be
reduced in the GOA, increased in the western NPO, and expanded to the Bering Sea. Future
climate warming may affect the ocean distribution, trophic conditions, and survival of
overwintering salmon, and the degree of the effects may be different among regional stocks or
age groups.
October 17, 11:50 (W2-9543)
Winter mortality of Okhotsk Sea pink salmon in the ocean
Alexander V. Zavolokin and Elena V. Strezhneva
Pacific Research Fisheries Centre (TINRO-Centre), Vladivostok, Russia. E-mail: zavolokin@tinro.ru
Winter mortality of Okhotsk Sea pink salmon varies greatly from year to year resulting in uncertainty in the forecast
of their returns the following year using data on their abundance in fall surveys. We examined size-selective
mortality of pink salmon and determined the possibility of utilizing body size of juvenile pink salmon to forecast
their returns. Scale increments of juvenile pink salmon caught in the southern Okhotsk Sea in fall 2007 and 2008
and of adult fish returning the following year were studied. For the 2007 generation of pink salmon that had very
low overwinter survival in the ocean, average scale increments during the first year of life for juvenile fish were
significantly lower than those of adult fish. For the 2008 generation of pink salmon that had very high overwinter
survival, scale increments of juvenile and adult fish were similar. These results corroborate the critical size-critical
period hypothesis which states that slowly growing juveniles that did not store up enough energy in summer and fall
have a stronger probability to die during the overwinter period compared to rapidly growing fish. Correlation
analysis showed significant negative relationships between body length, mass and mortality of pink salmon in the
ocean in 2001-2009. However, survival of the last pink generation (2012-2013) was unexpectedly low despite their
large body size. We speculate that although rapid growth is important it does not guarantee survival. Wintering
conditions can greatly influence pink salmon resulting in variations in their return strength.
October 17, 12:10 (W2-9583)
Impact of climate variability and change on winter survival of Bristol Bay sockeye salmon
Edward Farley1, Greg Ruggerone2, Phil Mundy1, Ellen Yasumiishi1 and Beverly Agler3
1
NOAA, NMFS, Alaska Fisheries Science Center, Auke Bay Laboratories, Juneau, AK, USA
E-mail: phil.mundy@noaa.gov
2
Natural Resources Consultants, Seattle, WA, USA
3
Alaska Department of Fish and Game, Mark, Tag and Age Laboratory, Juneau, AK, USA
Overwinter survival of Pacific salmon (Oncorhynchus sp.) is believed to be a function of size
and energetic status they gain during their first summer at sea. We test this hypothesis for Bristol
Bay sockeye salmon (O. nerka), utilizing data from large-scale fisheries and oceanographic
surveys conducted during mid-August to September 2002 to 2007. Specifically, we compared
distributions of mean circuli spacing during the first year at sea between juvenile salmon and
adult sockeye salmon scales to evaluate the magnitude of size-selective mortality during this life
stage. A probability curve of size-selective mortality in relation to weight (g) of juvenile salmon
was constructed. The juvenile size (weight) was then compared to summer/fall oceanographic
characteristics on the eastern Bering Sea shelf that may impact their growth rates and probability
of survival during winter. This analysis is placed within the context of previously published
results on summer/fall and winter marine ecology of Bristol Bay sockeye salmon and how
continued warming on the eastern Bering Sea shelf may impact their future growth (during
summer and fall) and survival during winter.
October 17, 14:00 (W2-9616)
Does physical environmental variation influence winter salmon habitat?
Shoshiro Minobe
Graduate School of Science, Hokkaido University, Sapporo, Japan
E-mail: minobe@sci.hokudai.ac.jp
Physical environmental variation associated with climate change and climate variability can
influence marine ecosystems in general, but to identify what aspects of physical variation affect
specific marine species is a challenge. In this paper, we examine whether and how the physical
environment influences winter habitat of salmon. The physical environmental parameters to be
examined include water temperatures, surface current velocities, and atmospheric sea-level
pressures. A primary focus will be on past variation, but future changes may also be examined
using CMIP5 model outputs where they are appropriate.