PICES XV
S7-3246
Invited
Relating recruitment mechanisms to life-history strategies for Alaskan groundfish
populations
Lorenzo Ciannelli and Kerim Aydin
Alaska Fisheries Science Center, NOAA, 7600 Sand Point Way NE, Seattle, WA, 98115-0070, U.S.A. E-mail: Kerim.Aydin@noaa.gov
Mechanisms linking climate to fish recruitment involve nested scales of complexity; from local effects such as
prey concentrations, turbulence, or light conditions to large-scale ecosystem effects such as food web shifts due
to increases in long-lived predators. A single recruitment “mechanism” (for example, as hypothesized through
correlations) may be a part of a larger pattern: a regime shift in climate may lead to a phase change in
mechanism (for example, from bottom-up to top-down control, or from local to large-scale bottlenecks) making
prediction via a single correlation-driven mechanism prone to error. Furthermore, the nature of the controlling
mechanisms may vary from stochastic models governed by a multitude of difficult-to-measure variables to
nonlinear models with few controlling variables but relatively unpredictable bursts of production. In spite of
these issues, the evolutionary results of climate-induced challenges to recruitment are quite visible. The
diversity of life history strategies among fishes may offer vital clues to the type of climate variation to which
different species have been exposed and become adapted. Here, we review hypothesized mechanisms linking
climate to the recruitment for several Alaskan groundfish stocks, and discuss analytical tools used to develop
and test mechanistic linkages in a manner that captures possible phase changes and nonlinearities. In doing so,
we pay specific attention to the relationships between analytical results, the scale of hypothesized mechanisms,
and the life history of periodic, opportunistic, and intermediate strategists: to what extent can the recruitment
patterns be inferred from a species’ position within this range of strategies?
PICES XV
S7-3058
Oral
Life history strategies of sea lice in the subarctic Pacific
Richard J. Beamish, Chrys-Ellen M. Neville and Ruston M. Sweeting
Pacific Biological Station, Fisheries and Oceans Canada, 3190 Hammond Bay Road, Nanaimo, BC, V9T 6N7, Canada
E-mail: Beamishr@pac.dfo-mpo.gc.ca
The sea louse, Lepeophtheirus salmonis, is commonly found on Pacific salmon that are rearing in the central
North Pacific Ocean and adjacent seas (subarctic Pacific). Large numbers of sea lice have also been observed
on all species of adult Pacific salmon when they return to coastal marine areas in the summer during their
spawning migration. Juveniles of these species of Pacific salmon inhabiting the same areas at the same time as
the returning adult salmon also have sea lice. Juvenile pink, chum and sockeye salmon will carry these sea lice
into the open ocean when they migrate away from the coastal areas later in the year. Juvenile coho and chinook
salmon that remain in the coastal areas can serve as hosts for the sea lice over the winter. The offspring of these
sea lice on pink, chum and sockeye can infect juvenile Pacific salmon on the high seas and the sea lice on coho
and chinook salmon can infect smolts and fry that enter the ocean in the early spring. We propose that the
transport of sea lice into coastal areas is a strategy employed by L. salmonis to improve their productivity by
improving the transmission potential of the infectious stage when host densities are decreased in the open ocean
and increased in the coastal areas.
PICES XV
S7-2804
Oral
The Ricker model and the pollock recruit abundance
Oleg Bulatov
Russian Federal Research Institute of Fisheries and Oceanography (VNIRO), 17 V. Krasnoselskaya Str., Moscow, 107140, Russia
E-mail: obulatov@vniro.ru
Many scientists believe that the Ricker model is most sensitive to the spawner-recruit relationship. Verification
of this model has shown that for pacific salmons this relationship had very low significance (Kotenev et al.,
2006). The Ricker model was used also to forecast the total allowable catch of Pollock in the Bering and
Okhotsk Seas. We used information on the abundance (biomass) of spawners and the numbers of recruit from
different authors (Wespestad, Traynor, 1988; Balykin, 1996; Ianelli et al., 2005) and examine the relationship
between these estimates by linear regression. The correlation was weak and inverse (R= - 0,21, in 1965-2004)
77
for the eastern Bering Sea, and it was slightly stronger for the western Bering Sea (R= 0,38, in 1970-1990). For
Okhotsk Sea Pollock no apparent relationship between the estimates was found (R= 0,09, Smirnov, 2005). We
also relied on linear regression to examine the relationship between the solar activity and chlorophyll a
concentration (R=0,6, for 1963-1994), the average water temperature (1 year before hatching) and the
abundance of generations (R=0,7, for 1966-1984), the fishery biomass lagged by 5 years and the average
temperature in July (R=0,6, for 1966-1984), and the fishery biomass lagged by 5 years and the solar activity
(R=0,6, for 1977-1999).
PICES XV
S7-3065
Oral
Using bioenergetics models to estimate sensitivity of California Current groundfish to
temperature anomalies
Chris J. Harvey
Northwest Fisheries Science Center, NOAA, 2725 Montlake Blvd. E, Seattle, WA, 98112, U.S.A. E-mail: chris.harvey@noaa.gov
The California Current is an eastern boundary current ecosystem with a highly diverse community of
groundfish, many of which are commercially and recreationally exploited. The groundfish assemblage is
characterized by multiple life history strategies that can be distinguished by differences in growth, maturation
rate, age, fecundity, egg size, and parental care. Because they co-occur in time and space, groundfish employing
these different strategies are often exposed to the same perturbations, whether of natural origin (e.g.,
temperature changes) or human origin (e.g., fishing). A precautionary or ecosystem approach to managing
diverse fish assemblages must be predicated on understanding the sensitivities of these life history types to
perturbations so that their responses can be anticipated and accounted for. Bioenergetic modeling of fish energy
budgets is one tool for generating quantitative estimates of the ecological impacts of ecosystem-level changes.
Using previously and newly developed bioenergetics models for representatives of the major groundfish life
history strategies in the Northern California Current ecosystem (rockfish, Sebastes spp.; Pacific hake,
Merluccius productus; English sole, Parophrys vetulus; leopard shark, Triakis semifasciata; lingcod, Ophiodon
elongatus), I am examining the responses of three variables (growth, consumption and reproductive output) to
temperature anomalies consistent with basin-scale oscillations and global climate change. These models
produce estimates of which life history strategies, and which size or age classes within each strategy, would be
most sensitive to temperature anomalies, and thus may require the most directed management attention within
the assemblage.
PICES XV
S7-2891
Oral
Fishing elevates variability in the abundance of exploited species
Chih-hao Hsieh1, Christian S. Reiss2, John R. Hunter1, John R. Beddington3, Robert M. May4 and George
Sugihara1
1
2
3
4
Scripps Institution of Oceanography, University of California - San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0202, U.S.A
E-mail: chsieh@ucsd.edu
Southwest Fisheries Science Center, National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA, 92037-1508, U.S.A.
Division of Biology, Faculty of Natural Science, Imperial College London, RSM Building, South Kensington campus, London, SW7
2AZ, United Kingdom
Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom
Separating the effects of environmental variability from the impacts of fishing on the dynamics of fish
populations is essential for sound fisheries management. We distinguish environmental effects from fishing
effects by comparing variability in the abundance of exploited versus unexploited species living in the same
environments. Using the 50-year-long larval fish time series from the California Cooperative Oceanic Fisheries
Investigations, we regard fishing as a treatment effect in a long-term ecological experiment. Here we present
the first direct large-scale evidence from the marine environment that exploited species exhibit higher temporal
variability in abundance than unexploited species. This remains true after accounting for life history effects,
abundance, ecological traits and phylogeny. The increased variability of exploited populations is likely caused
by fishery-induced truncation of the age structure, which reduces the capacity of populations to dampen
environmental variability. Thus, to avoid collapse, fisheries must be managed not only to sustain the total viable
biomass but also to prevent the significant truncation of age structure. A precautionary management approach is
warranted not only because of normal uncertainties associated with estimates of stock size but also because
fishing itself magnifies population variability.
78
PICES XV
S7-2863
Oral
Life cycle characteristics of the neon flying squid associated with the oceanographic
regime in the North Pacific
Taro Ichii1, Kedarnath Mahapatra2, Mitsuo Sakai1 and Denzo Inagake1
1
2
National Research Institute of Far Seas Fisheries, 2-12-4, Fukuura, Kanazawa-ward, Yokohama-city, 236-8648, Japan
E-mail: ichiil@affrc.go.jp
Tokai University Frontier Ocean Research Center (T-FORCE), 3-20-1, Orido, Shimizu-ward, Shizuoka-city, Shizuoka, 424-8610, Japan
Seasonal recruitment, growth, and migration patterns of the neon flying squid (Ommastrephes bartramii) were
examined in relation to oceanographic conditions in the North Pacific. O. bartramii undertakes an annual
round-trip migration between subtropical spawning grounds and subarctic feeding grounds, which is comprised
of an autumn and winter-spring spawning cohort. The autumn cohort grows faster during northward migration
whereas the winter-spring cohort grows faster during southward return migration. Males and females of the
autumn cohort follow separate migration patterns whereas those of the winter-spring cohort follow an almost
identical pattern. We addressed the following three questions: (1) Why is there a difference in growth patterns
between the cohorts? (2) Why are there differences in migration and distribution patterns between the cohorts?
(3) Why has the stock level of the autumn cohort been low since 1999? These issues can be explained using
seasonal as well as interannual meridional movements of the following two oceanographic zones: (a) optimum
spawning zone defined by the SST range: 21°C - 25°C; and (b) food-rich zone defined by position of Transition
Zone Chlorophyll Front (TZCF). Lower stock size of the autumn cohort in the recent years can be attributed to
the interannual variation in the TZCF position considering its possible contribution to the productivity in the
spawning ground, the Subtropical Frontal Zone.
PICES XV
S7-3106
Poster
Bioenergetics model of Japanese chum salmon (Oncorhynchus keta) growth
Yasuko Kamezawa1, Tomonori Azumaya2, Toru Nagazawa2 and Michio J. Kishi3
1
2
3
Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan
E-mail: kamezawa@ees.hokudai.ac.jp
Hokkaido National Fisheries Research Institute, Fisheries Research Agency, 116 Katurakoi, Kushiro, Hokkaido, 085-0802, Japan
Faculty of Fisheries Sciences, Hokkaido University, Sapporo, 060-0810, Japan
In the 1990s, a reduction of Japanese chum salmon body size was observed. The change of zooplankton density
as prey, and/or their population density effect are proposed by many studies. In order to investigate this body
size reduction of Japanese chum salmon in the North Pacific, we developed a bioenergetics model for chum
salmon. Our model was based on NEMURO.FISH (Ito et al., 2004) using respiration and consumption terms
(Ware, 1978; Beauchamp et al., 1989) and assumed that SST and prey zooplankton density are the determining
factors of the reduction of body size. SST and prey zooplankton density are obtained from the result of
NEMURO embedded in 3-D physical model (Aita-Noguchi et al., 2006), along the migration root of chum
salmon. The period of foraging migration is supposed to be four years and the life stage of Japanese chum
salmon is divided into eight stages, i.e. four stages for summer and the other four for winter. The model
reproduced the body size of the 1972 and 1991 year classes of chum salmon, respectively. Reproduced body
size of the 1972 year class is larger than that of 1991 year class. This result shows a good agreement with the
observations in the Bering Sea. Moreover, our model reproduces the trend of observations in l970-2000 well.
The prey density, especially in the Eastern North Pacific, has a larger influence on the change of body size than
SST does. This suggests that the size reduction of Japanese chum salmon in 1990s was partly affected by prey
zooplankton density.
79
PICES XV
S7-3017
Poster
Seasonal variability in feeding habits in the larval stage of three clupeoid species in Tosa
Bay, southern Japan
Hiroshi Kubota1, Tatsuya Kaji2, Nobuhiro Saito3, Akinori Takasuka1 and Yoshioki Oozeki1
1
2
3
Stock Assessment Division, National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa,
Yokohama, Kanagawa, 236-8648, Japan. E-mail: miles@affrc.go.jp
Kochi Prefectural Fisheries Experimental Station, 1153-23, Uranouchi-Haikata, Susaki, Kochi, 785-0167, Japan
Suido-sha Co. Ltd., 8-11-11, Ikuta, Tama, Kawasaki, Kanagawa, 214-0038, Japan
The links between fish species replacement and zooplankton dynamics owing to climatic regime shift are often
complex. For instance, anchovy flourish and sardine often collapse in the same regime and in several
ecosystems. Through gut content analysis, we tested the hypothesis that the difference in feeding habits among
species would solve a part of this complexity. The study area was set in Tosa Bay, southern Japan, where
Japanese sardine consistently spawned every early spring even after the collapse of the sardine stock. We
collected larval fishes from the commercial fishery catch by a shirasu-patch net from November 2003 to April
2004, analyzed the gut content of 1,500 individuals and compared its composition among the dominant three
clupeoid species (Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus and round
herring Etrumeus teres) of 10–38 mm in SL. Gut content composition differed little between the three species
when compared in the same season, but the dominant fish species and their main prey changed seasonally, e.g.
Paracalanus spp., Clausocalanus spp., Calanus spp. and Candacia spp. in February and March. We conclude
that food selectivity seldom varies among larvae of these species, and that their food changes synchronously
with the seasonal variations in zooplankton fauna. Seasonal match-mismatch between the zooplankton bloom
and larval feeding (or spawning) seasons of each species could be more important than food selectivity, as the
zooplankton bloom and larval feeding may shift several weeks or months with the yearly fluctuations in water
temperature.
PICES XV
S7-3020
Oral
Variations in recruitment of small pelagic species around Korean waters
Jae Bong Lee1, Chang Ik Zhang2, Anne Hollowed3, Dong Woo Lee1, and Sang Cheol Yoon1
1
2
3
National Fisheries Research and Development Institute, 408-1, Shirang-ri. Gijang-up, Gijang-gun, Busan, 619-902, Republic of Korea
E-mail: leejb@nfrdi.re.kr
Pukyong National University, 599-1, Daeyeon3-dong, Nam-gu, Busan, 608-737, Republic of Korea
Northwest Fisheries Science Center, NOAA, 2725 Montlake Blvd. E, Seattle, WA, 98112, U.S.A.
Marine fish species with pelagic eggs or larvae often show substantial fluctuations in recruitment, which may be
attributed to environmental factors affecting early life stage’s abundance, growth and survival. Environmentrecruitment relationships have been studied in highly productive areas such as shelf areas of the Northwestern
Pacific, including Korean waters where environmental factors showed relatively clear patterns and there was
general understanding of casual links between ocean physics, plankton productivity and recruitment success.
Because small pelagic fishes are usually short-lived, any fluctuation in recruitment success translates rapidly
into fluctuations in population size. Therefore, what may be a conservative level of exploitation during years
with good recruitment may result in overfishing during unfavorable years. Recruitment success can be thought
of as an integrated function of processes acting across a wide range of life-history stages, from the size and
condition of the spawning population at one end to the pre-recruit survival rates at the other. The objective of
this study is to investigate an abrupt shift, that is, a discontinuity in ocean environmental time series data of
Korea and adjacent waters for 1968-2004. We hypothesized that successful recruitment was dependent on
advection processes; specifically, eggs and larvae of small pelagics were transported from spawning grounds in
the ECS to nursery grounds in the southwestern Korean peninsula. The recruitment of small pelagics is
dependent on the abundance of spawning biomass in the previous year and advection during the spring.
80
PICES XV
S7-3105
Poster
Interdecadal variability on the growth and migration trajectory patterns of Pacific
saury: A model-based study
Daiki Mukai1, Michio J. Kishi1,2, Shin-ichi Ito3, Yasuhiro Yamanaka1,2 and Fumitake Shido1
1
2
3
Graduate School of Environmental Science, Hokkaido University, N10W5, Kita-ku, Sapporo, 060-0810, Japan
E-mail: dmukai@ees.hokudai.ac.jp
Frontier Research Center for Global Change, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001, Japan
Tohoku National Fisheries Institute, 3-27-5, Shinhama, Shiogama, Miyagi, 985-0001, Japan
Pacific saury is mainly located in North Pacific and is one of the important fisheries in Japan. Saury migrates
widely in the North Pacific. However, saury growth and stock vary widely from year to year, and the cause for
these fluctuations is unclear due to paucity of data. A modeling approach is useful to investigate physical and
biological processes responsible for variation of saury biomass and growth rate. This modeling study focuses on
interdecadal variability of Pacific saury growth and their migration trajectory patterns. The saury model is
linked with 3-D lower trophic biological model consists of multiple phytoplankton and zooplankton. The model
is based on a biomass-based model, NEMURO.FISH of PICES (Ito et al., 2004). The results show that saury
growth rate tends to be higher after the 1976/77 Pacific climate shift due to the modeled zooplankton biomass
increase after the 1976/77 climate shift, which correlate well with the Pacific Decadal Oscillation (PDO).
During the positive PDO phase, the mixed water region tends to be colder with deeper mixing during the winter
and early spring. Therefore spring phytoplankton productivity is higher, which result in higher zooplankton
biomass. For saury migration trajectory patterns, our study results that most of saury are advected to the east of
160°E through their southward migration in winter because of strong eastward current and never back to near
Japan. Conversely, few saury can migrate back to near Japan, and some of them are caught as one of important
commercial fisheries in Japan.
PICES XV
S7-2991
Poster
Predation on larval and juvenile anchovy by skipjack tuna in the Kuroshio - Oyashio
transition region
Sayaka Nakatsuka1, Akinori Takasuka2, Hiroshi Kubota2 and Yoshioki Oozeki1,2
1
2
Course of Marine Life Sciences, Tokyo University of Marine Science and Technology, 4-5-7 Kounan, Minato, Tokyo, 108-8477, Japan
E-mail: nakatsuk@affrc.go.jp
National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa, Yokohama, Kanagawa, 2368648, Japan
Daily ration of skipjack tuna (Katsuwonus pelamis) on larval and juvenile anchovy (Engraulis japonicus) was
assessed using samples of skipjack tuna and anchovy captured simultaneously through a cooperative cruise
comprising two research vessels in the Kuroshio–Oyashio transition region in May and June 2005. Young
anchovy were sampled using a frame trawl (MOHT: 5 m2 mouth opening), while skipjack tuna were captured
with a drift net. To quantify the predation effect of skipjack tuna on young anchovy, the digestive tracts of 100
individuals (390–510 mm in SL) were divided into five parts (stomach, pylorus, duodenum, bowel, and rectum)
and examined. The contents were sorted by stage of digestion and prey items were identified. We estimated the
number of larval and juvenile anchovy ingested by counting otoliths as well as undigested individuals. Standard
length and wet weight of anchovy found in the gut of skipjack tuna were reconstructed from the otolith radius.
The larval and juvenile anchovy dominated 65% of stomach contents in number, and more than 98% of the
contents of the other parts of the digestive tract. Estimated standard length of anchovy preyed upon by skipjack
tuna were similar in range to those of anchovy captured by the trawls (n = 1382, 13.6–40.6 mm in SL), although
the mean size of ingested anchovy was larger than the mean size obtained from the trawl. An individual
skipjack tuna fed on 274 ± 175 (mean ± SD) larval and juvenile anchovy and 22.0 ± 14.1 g in weight per day.
This corresponded to approximately 1.2% of the skipjack tuna’s wet body weight.
81
PICES XV
S7-3222
Oral
An early life history model for Pacific herring in Prince William Sound, Alaska
Brenda L. Norcross, Sean-Bob Kelly, Peter-John Hulson and Terrance J. Quinn II
School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK, 99775-7220, U.S.A.
E-mail: norcross@ims.uaf.edu
Our modeling efforts support Hjort’s concept of mortality in the larval stages as the most “critical period” in
determining year-class strength of herring fisheries. Using published data, we integrated information about
survival in egg, larval and juvenile life stages into a mathematical model that used means and standard
deviations to characterize the early life history of Pacific herring (Clupea pallasii) in Prince William Sound
(PWS), Alaska. The early life history model predicted survival after the first year to be 118 herring out of one
million eggs and a 95% confidence interval of 5 - 2,822 herring. Survival estimates differed for all life stages in
the first year, with survival the lowest in the larval stage. Estimates of survival of the egg stages, fall juveniles
and winter juveniles were two orders of magnitude greater than the survival of larvae. The single-stage
sensitivity analysis demonstrated that for age-0 herring the influence of altering daily mortality resulted in an
estimated total survival that was not equivalent for each life stage. The largest influence to the total survival
was by increasing or decreasing the daily mortality in the larval stage. The results of the interaction sensitivity
analysis of all possible paired life stages affirmed the results of the single life stage sensitivity, i.e., the larval life
stage, in combination with any other life stage, contributed the most to total survival of first year herring.
Environmental processes, including food availability, water temperature, and transport processes, act on the
larval stage to determine survival of Pacific herring.
PICES XV
S7-3009
Oral
Patchiness structure and mortality of Pacific saury, Cololabis saira, larvae in the
northwestern Pacific Ocean
Yoshioki Oozeki1, Ryo Kimura2, Hiroshi Kubota1 and Hiroshi Hakoyama1
1
2
National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa, Yokohama, Kanagawa, 2368648, Japan. E-mail: oozeki@affrc.go.jp
Headquarters, Fisheries Research Agency, 2-12-4, Fukuura, Kanazawa, Yokohama, Kanagawa, 236-8648, Japan
Patchiness structure and mortality rate of Pacific saury, Cololabis saira, larvae were studied in the KuroshioOyashio transition zone in May 2000 and 2001. Dense larval distribution areas were detected during
preliminary surveys and were marked using GPS-buoys equipped with drogues. Random neuston-net (1.3 m
mouth width, 0.45 mm mesh) sampling was repeatedly conducted at night in the 5 nautical square miles with
tracking the buoys every other day. Nine data sets (a total of 221 net samples) provided four pairs for larval
mortality analysis. Average density of larval patchiness was estimated as 1.4 patches 100 km-2 and the patch
size was estimated as 23.7 km2. The average distance between the gravity centers of patches was 8.4 km. These
parameters of patchiness of the saury larvae remained consistent over the course of the study. Hence, larval
mortality was estimated on every 5 mm knob length (KnL) intervals without considering the diffusion rate.
Larval growth was examined through otolith increment analysis. The estimates of mortality ranged from 30 to
40 % for larvae of 10 to 40 mm in KnL and did not decrease during the larval and juvenile stage. Negative
mortality rate, estimated on larvae smaller than 10 mm KnL, suggested a continuous hatching of saury larvae in
this area.
82
PICES XV
S7-3081
Oral
Can we explain and predict stock fluctuations of Japanese common squid, Todarodes
pacificus, related to climatic regime shifts?
Yasunori Sakurai1, Jun Yamamoto2, Ken Mori3, Tsuneo Goto4 and Hideaki Kidokoro4
1
2
3
4
Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, 041-8611, Japan. E-mail: sakurai@fish.hokudai.ac.jp
Hakodate Branch, Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Hokkaido, 041-8611, Japan
Hokkaido National Fisheries Research Institute, Kushiro, 085-0802, Japan
Japan Sea National Fisheries Research Institute, Niigata, 951-8121, Japan
Annual catches of Japanese common squid, Todarodes pacificus, decreased during a cool regime period from
the late-1970s to late-1980s, and have increased during the recent warm regime period after the late-1980s. The
catch fluctuations are similar to those of Jack mackerel and Japanese anchovy. T. pacificus produces gelatinous,
nearly neutrally buoyant egg masses that contain many small eggs. The egg masses are thought to occur within
or above the pycnocline at temperatures suitable for egg development. Recently, we estimated from laboratory
studies that hatchlings (< 1mm ML) will ascend to the surface at temperatures between about 18-23ºC. After
hatching, the paralarvae presumably ascend to the surface layer from the mid layer near the pycnocline above
the continental shelf and slope and are advected into convergent frontal zones. We used this new reproductive
hypothesis to explain and predict the stock fluctuations in relation to climatic regime shifts. During warm
regime period after 1989, the inferred spawning areas of winter spawning group have occurred along the
continental edge off the Kyushu Island and the Nansei Islands, and the inner flow of the Kuroshio has
transported the hatchlings in the surface layer from the spawning areas to the nursery areas of northeastward
along the continental edge. However, the spawning areas during the cool regime of the 1980s vanished along
the continental edge, when winter wind stress was stronger, and air temperature at the sea surface was lower,
and mixed layer depth at the spawning grounds was deeper than those after 1989. We conclude that prospective
change of T. pacificus stock can predict by physical parameters such as wind stress, air temperature, SST, and
MLD during the spawning period based on a new reproductive hypothesis.
PICES XV
S7-2902
Oral
Analysis of key recruitment processes for Euphausia pacifica off the Oregon coast
C. Tracy Shaw1, Leah R. Feinberg1, Hongsheng Bi1 and William T. Peterson2
1
2
Cooperative Institute for Marine Resources Studies, Oregon State University, 2030S Marine Science Drive, Newport, OR, 97365, U.S.A.
Email: tracy.shaw@oregonstate.edu
Northwest Fisheries Science Center, NOAA, 2030 South Marine Science Drive, Newport, OR, 97365, U.S.A.
The euphausiid Euphausia pacifica is widely distributed throughout the Pacific Ocean. It is often the dominant
species of euphausiid found throughout a wide range of ocean conditions, from warm inland seas to the cold and
food-limited open ocean. We will investigate the recruitment processes of this species, including brood size,
development time and growth rate, in relation to environmental conditions (i.e.: warm or cold ocean regime) to
determine temporal variability in spawning and the subsequent effect on recruitment. Survivorship curves and
development time measurements from work conducted in our laboratory show that the early developmental
stages C1 and FIII are considerably slower than other stages. We will use these measurements to determine how
varying the development time of particular stages affects recruitment. We will also investigate the effect of
warm and cold ocean conditions on recruitment. Experiments on spawning, growth and larval development
show high variability among individuals. E. pacifica seems to apply a plastic life history strategy of being
highly variably in each of these vital rates under all environmental conditions. As a consequence, we suggest
that modeling of euphausiids should be conducted using individual-based models to accurately represent this
variability. This is a more complicated process, but will yield results that reflect the actual population dynamics
of Euphausia pacifica.
83
PICES XV
S7-3224
Oral
Parent-progeny relationships in the Okhotsk Sea walleye pollock
Anatoly V. Smirnov
Pacific Research Fisheries Centre (TINRO-Centre), 4 Shevchenko Alley, Vladivostok, 690950, Russia. E-mail: smirnov@tinro.ru
Data on the number of spawning adults and the abundance of recruits of walleye pollock (Theragra
chalcogramma) in the Okhotsk Sea, collected during 1984-2004, have been analyzed. It appears that the
survival of walleye pollock during the first year of life is not correlated with the abundance of parents (r=0.09).
It implies that, under equal conditions, the probability for the appearance of high-yielding generation is higher
when the number of spawners is high. Such a relationship had statistical support (r=0.67). We may suggest
that, for the rather large population of the Okhotsk Sea walleye pollock, the classical reproduction curve
(Rickers’s model) is not applicable. Mainly environmental factors and, to a lesser extent, the number of
spawners, produce a measurable influence on walleye pollock survival in early ontogenetic stages. In particular,
the higher the share of first-time spawning females, the lower the survival of their progeny. In certain years,
high survival rates of the progeny were due to large mean size and high mean age of spawning females, and
their lower relative abundance in a spawning stock. However, such a relationship appeared insignificant, when
long-term data were taken into account. We suggest that a combination of favorable environmental factors,
medium or high abundance, optimal size-age structure of the spawning stock and “quality” of spawners favor
the appearance of strong generations in populations of walleye pollock.
PICES XV
S7-2855
Oral
The effect of spawner age on stock productivity: Influences of life-history pattern and
recruitment variability
Paul D. Spencer
Alaska Fisheries Science Center, NOAA, 7600 Sand Point Way NE, Seattle, WA, 98115-0070, U.S.A. E-mail: paul.spencer@noaa.gov
Marine fish stocks exhibit a wide variety of responses to oceanographic variability and harvesting, reflecting
largely differences in reproductive biology and stock-recruitment relationships. In particular, for some stocks
(Pacific rockfish and Atlantic cod) there is evidence that larval viability may be affected by the age of the
spawner, thus potentially complicating stock-recruitment relationships. These maternal effects can be viewed as
redefining the units of spawner output from eggs to “viable larvae”, and for Alaska Pacific ocean perch (POP)
this redefinition has produced increased estimates of resiliency by associating a given time-series of recruitment
estimates with a diminished measure of spawner output. Additionally, harvesting would be expected to have a
substantial role in the production of viable larvae via truncation of the stock age-structure. In this study,
simulated “cod-like” and “rockfish-like” populations are used to further explore how estimates of stock
productivity may be affected by life-history pattern, recruitment variability, and exploitation. Production of
viable larvae may be affected by density-dependent and/or density-independent mortality, and traditional stockrecruitment functional forms will be modified to consider the effect of spawner age.
PICES XV
S7-2833
Invited
A population dynamics model for Japanese sardine, Sardinops melanostictus, off the
Pacific coast of Japan, consisting of spatial early-life stage and age-structured adult submodels
Maki Suda, Tatsuro Akamine and Hiroshi Nishida
National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa, 2368648, Japan. E-mail: msuda@affrc.go.jp
We constructed an individual-based life cycle model for the Japanese sardine, Sardinops melanostictus, off the
Pacific coast of Japan, consisting of spatial early-life stage and age-structured adult sub-models. Japanese
sardine has exhibited dramatic changes in its stock abundance. Our simulation approximately reproduced these
fluctuations during 1978-2002, using this life cycle model. Stock fluctuations of Japanese sardine are thought to
be caused mainly by differences among years in the mortality rate before recruitment. Our multiple cells model
showed the population dynamics in the early life stages under heterogeneous environmental conditions, by
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incorporating information on differences in the environment of each of the cells. Our model determined the
natural mortality by using the information of the environmental conditions, interspecific-relationship and the
density-dependent effects. Also in the age-structured adult sub-model, our model determined the number of
surviving fish by using the natural mortality and the fishing mortality. That is, we considered the influence of
environmental factors (water temperature and food density), interspecific relationship and fishing mortality to
investigate the causes of the Japanese sardine stock fluctuation. Our simulation revealed that the decline of the
sardine stock in the 1990s could not have been halted by catch regulations; however, the slope of the decline in
the 1990s could have been mitigated by a reduction of the fishing mortality. Our approach allows flexibility and
extensibility in the model. If more observed data are accumulated, the future versions will incorporate a more
explicit spatial approach and a multispecies model.
PICES XV
S7-2926
Poster
Comparison of growth rate between hatching months of Pacific sandlance Ammodytes
personatus in early life stages
Kai Sugiyama1, Tetsuya Takatsu1, Yasuyoshi Fukui1 and Mikimasa Joh2
1
2
Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, 041-8611, Japan
E-mail: sugikai4@fish.hokudai.ac.jp
Hokkaido Abashiri Fisheries Experimental Station, Masu’ura Abashiri, Hokkaido, 099-3119, Japan
To clarify the population fluctuation mechanism of Pacific sandlance Ammodytes personatus, we examined
growth history by using an otolith back-calculation method of the pelagic larvae and settled juveniles collected
in Mutsu Bay, Japan from January to May in 2003-2005. Pelagic larvae of Pacific sandlance were collected
with a ring net and MTD closing nets mainly from February to April in the bay, and settled juveniles were
obtained from commercial landings of dip nets individuals with fishing lamps from the coastal area of the bay
mouth in May. Hatch date distributions for pelagic larvae and settled juveniles through the three years were 1%
in number in January, 15% in February, 68% in March, and 16% in April, and 1% in January, 33% in February,
65% in March, and 1% in April, respectively. The logistic growth equations were obtained as follows:
BL=82.00/(1+exp(2.530-0.031·age)), for the individuals hatched in February, BL=73.55/(1+exp(2.4240.038·age)), for those in March, and BL=73.55/(1+exp(2.469-0.042·age)), for those in April. In all three years,
early hatched individuals showed low growth rates and water temperature increased from March. Densities of
copepod nauplii as the primary prey for small larvae and copepodites as prey for large larvae were roughly
steady from February to April in these three years. Thus, growth rates in larval and early juvenile periods of
Pacific sandlance might be mainly enhanced by high water temperature rather than by high prey abundance.
Settled juveniles had relative wider otolith increments near the outer margins than pelagic individuals which
showed similar body size.
PICES XV
S7-2939
Oral
Growth of larval and early juvenile sardine (Sardinops spp.) and anchovy (Engraulis
spp.) in the eastern and western North Pacific Ocean
Motomitsu Takahashi1, David M. Checkley Jr.1, Akihiko Yatsu2 and Yoshiro Watanabe3
1
2
3
Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA, 92039-0218, U.S.A.
E-mail: takahamt@coast.ucsd.edu
Hokkaido National Fisheries Research Institute, Fisheries Research Agency, 116 Katsurakoi, Kushiro, Hokkaido, 085-0802, Japan
Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639, Japan
We hypothesize that both food and temperature control the growth of larval and juvenile sardine and anchovy.
Growth rates of larval and early juvenile sardine and anchovy were estimated from daily increments of otoliths
and examined in relation to sea surface temperature (SST) and the concentration of available copepods in the
California Current and Kuroshio/Oyashio regions. Pacific sardine Sardinops sagax and northern anchovy
Engraulis mordax were collected off California, Oregon, and Washington in spring, summer, and autumn.
Japanese sardine S. melanostictus and anchovy E. japonicus were collected in the Kuroshio-Oyashio transition
in spring. Otolith and somatic growth rates of S. melanostictus and E. japonicus were faster than those of
S. sagax and E. mordax. We standardized the individual growth rate to remove the effect of fish size.
Standardized recent growth rate (SRGR) for the five days before capture varied positively over 12-20°C SST for
S. melanostictus and E. japonicus, while SRGR decreased over 17-20°C SST for S. melanostictus. SRGR for
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S. sagax and E. mordax was in the lower range of SRGR for S. melanostictus and E. japonicus. SRGR of
E. mordax was significantly less than that of E. japonicus over 13-16°C SST; there were insufficient data for
this analysis for Sardinops. The concentration of copepods available to E. mordax in the California Current
region was significantly lower than that for E. japonicus in the Kuroshio-Oyashio transition region. We
conclude that both food and temperature affect the growth rate of larval and juvenile anchovy and sardine in the
regions studied.
PICES XV
S7-3163
Poster
Impact of the late 1980s regime shift on the abundance and distribution of loliginid
squid Loligo bleekeri in the southwestern Japan Sea
Yongjun Tian
Japan Sea National Fisheries Research Institute, Fisheries Research Agency (FRA), Suidou-cho, Niigata, 951-8121, Japan
E-mail: yjtian@fra.affrc.go.jp
An oceanic regime shift, as indicated as an abrupt change from colder to warmer water in the Tsushima Warm
Current (TWC), was identified in the late-1980s in the Japan Sea and largely associated with fish population
dynamics. The loliginid squid Loligo bleekeri is a commercially important species for coastal fisheries in Japan.
Catch from the southwestern Japan Sea reached the maximum of 13,700 tons in 1977, but has been decreased to
less than 100 tons in recent years with large interannual fluctuations. Using monthly trawl catch data with a
resolution of 30 minutes (longitude-latitude) for the southwestern Japan Sea during 1975-2004, we examined the
impact of fishing and the late 1980s regime shift on the abundance and distribution of the squid.
The catch of loliginid squid shows decadal variations with a change from positive to negative anomalies
occurring around the late 1980s. This pattern corresponds well with the changes in water temperature in TWC
from cold to warm regime that occurred in late 1980s, strongly indicating that the decadal variability in loligind
squid was largely affected by the late 1980s regime shift. DeLury analysis showed that fishing mortality
averaged during 1989-2000 is about 3 times higher than that during 1975-1988, and the exploitation rate
increased from 50% to 80% during the last three decades, indicating that intensified fishing mortality
accelerated the collapse of the stock. GIS mapping showed that the distribution area in the south of Tsushima
Is. almost disappeared, and the decreasing pattern in distribution and abundance corresponded with the warming
and northward shift in winter sea temperatures front of TWC. These suggest that decadal variation patterns in
the squid largely forced on the regime shift of TWC, while fishing has a large impact on the interannual
variation and the collapse of the stock.
PICES XV
S7-2932
Oral
Climate variation and salmon recruitment: Comparing climate indices for predicting
salmon marine survival in the Northern California Current ecosystem
Thomas C. Wainwright1, Richard D. Brodeur1, Robert L. Emmett1, Peter W. Lawson1, William T. Peterson1,
James J. Ruzicka2 and Laurie A. Weitkamp1
1
2
Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration, 2032 SE OSU Drive, Newport, OR, 97365,
U.S.A. E-mail: thomas.wainwright@noaa.gov
Cooperative Institute for Marine Resources Studies, Oregon State University, Hatfield Marine Science Center, 2030 SE Marine Science
Drive, Newport, OR, 97365, U.S.A.
Interannual to decadal scale climate fluctuations have a strong influence on recruitment of Pacific salmon
(Oncorhynchus spp.), as evidenced by numerous studies linking various long-term climate indices (regional
upwelling, local sea surface temperature, date of the spring transition, ENSO indices, PDO, etc.) with salmon
commercial catch as a proxy for stock abundance. The anadromous life history of salmon complicates
interpretation of these results. Researchers have recently focused on using these climate indices to directly
explain variation in salmon marine survival for stocks where freshwater production, harvest, and adult
escapement are adequately monitored to estimate marine-phase survival. To date, these studies have focused
primarily on indices of the physical climate. However, during the past decade, increased biological sampling in
the Northern California Current (NCC) has provided a number of biological indicators of ecosystem status (e.g.,
plankton production, copepod community structure, and abundance estimates for juvenile salmon, forage fishes,
and predaceous fishes). We compare the utility of various physical and biological indicators (including both
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ocean and freshwater environments) as salmon forecasting tools by putting these various indicators in a
consistent statistical framework and assessing their effectiveness as short-term forecast tools for three salmon
production indices: Oregon Production Index (OPI) coho salmon marine survival, Oregon Coast natural (OCN)
coho salmon recruits per spawner, and Snake River spring/summer Chinook salmon marine survival. We also
propose a statistical “ensemble” forecast model that combines the various indices in a decision-support
framework to provide integrated recruitment forecasts along with an assessment of uncertainty.
PICES XV
S7-2937
Oral
Crab larval advection and recruitment in the Eastern Bering Sea
Jie Zheng1 and Gordon H. Kruse2
1
2
Alaska Department of Fish and Game, Commercial Fisheries Division, P.O. Box 115526, Juneau, AK, 99811-5526, U.S.A.
E-mail: Jie_Zheng@fishgame.state.ak.us
School of Fisheries and Ocean Sciences, Juneau Center, University of Alaska Fairbanks, 11120 Glacier Highway, Juneau, AK, 998018677, U.S.A.
Spatial distributions of red king and snow crabs in the eastern Bering Sea changed profoundly during the last
three decades. The shifts of distributions to the northeast for mature female red king crabs occurred right after
the 1976/77 regime shift, while the shifts of mature female snow crabs to the northwest occurred from the mid1970s to early 1980s. Because distribution centers of small juvenile red king and snow crabs are generally
located downstream of the mature females, advection may be an important process for red king and snow crabs.
In this study, we used the OSCURS model to simulate annual larval drifts from 1967 to 2004 for red king crabs
and from 1975 to 2004 for snow crabs. Larval durations were estimated to range from 44 days to 153 days for
red king crabs and from 59 days to 153 days for snow crabs, with longer durations for the earlier hatching
larvae. The northward shifts of spatial distributions of mature females made it difficult to supply larvae to the
southern portions of their ranges. Larvae hatched in the north of their habitat might have greater chances of
settling on unfavorable habitats than in those hatched in the south. Changes in settling locations over time might
have affected recruitment strength for Bristol Bay red king crabs. However, simulated larval locations cannot
consistently explain the strong and weak year classes for snow crabs. Larval advection may be one of many
important factors influencing crab year class strengths.
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