Sardinops Research Articles

Interannual and Secular Variability of Larvae of Mesopelagic and Forage Fishes in the Southern California Current System

AbstractWe used univariate and multivariate spatiotemporal delta models to quantify changes in the distribution of ichthyoplankton in the southern California Current System from 1951 to 2016. We focus on mesopelagic species, because they are most abundant, and on northern anchovy (Engraulis mordax), Pacific sardine (Sardinops sagax), and Pacific hake (Merluccius productus), because they are important commercial and forage fish species. Univariate models indicated that changes in the relative abundance, area occupied, center of gravity, and spatiotemporal variability of numerically dominant warm‐water and cool‐water‐associated mesopelagic ichthyoplankton show strong species‐specific differences. Multivariate models revealed that the warm‐water‐associated mesopelagic assemblage exhibits an increasing, nonmonotonic, secular trend of increasing relative abundance underlying interannual variability, suggesting a tropicalization of the southern California Current System. In contrast, the cool‐water‐associated mesopelagic assemblage shows mainly interannual variability, with little secular trend over the 65‐year period. Correlation matrices of the modeled ichthyoplankton densities showed that the spatial distributions of northern anchovy and Pacific hake are highly correlated with cool‐water mesopelagic ichthyoplankton, but Pacific sardine is spatially correlated with both warm‐ and cool‐water‐associated mesopelagic species. Declines of adult sardine, anchovy, and hake are occurring concurrently with tropicalization of the southern California Current System. The most parsimonious explanation for tropicalization of the ichthyoplankton is increased presence of Pacific Equatorial‐influenced Water in the inshore southern California region.

Spawning patterns provide further evidence for multiple stocks of sardine (Sardinops sagax) off eastern Australia

AbstractPrevious studies have suggested that sardine, Sardinops sagax, off eastern Australia spawns across its entire range when habitat conditions are suitable. However, recent studies have suggested that separate sub‐populations and spawning groups may occur in the region. Spawning patterns off eastern Australia were investigated using data collected during nine ichthyoplankton surveys conducted between 1997–2015, and adult reproductive data obtained from ad hoc commercial sampling off New South Wales (NSW). The egg surveys covered the known distribution of sardine off eastern Australia and included year‐round sampling in the northern and southern parts of this range. Egg distributions and analysis of gonadosomatic indices identified two spatio‐temporally separate spawning groups; one occurring off southern Queensland to northern NSW during late winter and early spring, and a smaller group off eastern Tasmania to southern NSW during summer. Most eggs were collected from waters 50–90 m deep, with sea surface temperatures of 18–23°C. Additive modelling indicated depth was the most significant factor driving selection of spawning habitat, followed by the interaction of month and latitude. Low egg densities were recorded in waters between 34–37°S, despite conditions within the ranges suitable for spawning. The presence of two spawning groups of sardine off eastern Australia supports recent findings that two sub‐populations occur in the region. Findings of this study will help to optimise the spatio‐temporal extent of future egg surveys and further confirm the need to coordinate future management of each sub‐population among relevant jurisdictions.

Laboratory comparison of potential natural baits for potting New Zealand scampi, Metanephrops challengeri

The effectiveness of potting methods for harvesting seafood is heavily reliant on the attractiveness of the bait to the target species. Consequently, the introduction of potting methods for a new species requires a method for more quickly screening the attractiveness of potential baits without the need for experimentally deploying large numbers of pots. Here, we developed a laboratory method for quantifying the attractiveness of six natural baits and a positive control to a deep-sea lobster species, New Zealand scampi, Metanephrops challengeri (Balss, 1914), using a binary choice flume. Scampi had the highest levels of attraction to pilchard, Sardinops sagax (Jenyns, 1842), and minced pilchard bait bound with alginate. A polychaete meal bait bound with alginate released free amino acids at the highest rate, but elicited a weaker attraction response from scampi, suggesting that the chemical profile, rather than the quantity of amino acids released by the bait, is more important in eliciting a response. This was confirmed by the similar response of scampi to minced pilchard baits bound with alginate containing 1% and 10% by wet weight, a result that would potentially allow for the reduction of the amount of pilchard tissue required for forming baits for use in commercial potting. The results indicate that laboratory methods can be used to provide a rapid assessment of the attractiveness of a variety of potential baits to a target species prior to deployment in potting experiments in the field.

Performance of fish-habitat classifiers based on derived predictors from a coupled biophysical model

Abstract Fish habitat models based on remotely-sensed data may be limited by satellite coverage and availability. We compared the fit and predictive power of Random Forest habitat classifiers that were developed using predictors derived from a coupled biophysical model (i.e., modeled predictors) versus similar classifiers that used remotely-sensed satellite data for two data sets (eggs and adults) and four species that occur widely in the California Current system. When tested on independent data, classifiers of spawning habitat that used derived predictors (derived classifiers) had nearly identical accuracies (0–2% difference) to similar classifiers based on satellite data (satellite classifiers). Accuracies of derived classifiers of adult habitat were within −8% to +7% of comparable satellite classifiers. Accuracies of both types of classifiers on test data were much greater for Northern anchovy Engraulis mordax and Pacific hake Merluccius productus (0.75–0.97) than for jack mackerel Trachurus symmetricus and Pacific sardine Sardinops sagax (0.61–0.72), and generally were greater for classifiers of spawning habitat than for adult habitat. Specificity was very good for both types of classifiers, but sensitivity was poor, because classifiers identified potential habitat which was not fully occupied. Adults of all species used a broader range of habitat conditions during summer than during the spring spawning period. Derived classifiers have some advantages over satellite classifiers; they are not limited by cloud cover and they can make predictions in near real-time or the short-term future. However, there was no consistent improvement in the accuracy of derived predictors that included modeled zooplankton concentrations over comparable satellite classifiers that included reflectance/chlorophyll concentration.

Thermal Effect of Acute and Chronic Stress on Hepatic and Renal Tissue of the Pacific Sardine, Sardinops sagax caeruleus (Jenyns, 1842)

Thermal Effect of Acute and Chronic Stress on Hepatic and Renal Tissue of the Pacific Sardine, Sardinops sagax caeruleus (Jenyns, 1842)

A frame-based modelling approach to understanding changes in the distribution and abundance of sardine and anchovy in the southern Benguela

A number of ecologically and economically important species in the southern Benguela, including the forage fish sardine Sardinops sagax and anchovy Engraulis encrasicolus, have undergone southward/eastward shifts in their distribution in the 1990s/early 2000s. In addition to the effects of changes in prey availability to top predators, the spatially-distinct nature of the system means the location of a stock has implications for its productivity. The spatial dynamics of small pelagic fish are of particular importance because they are thought to exert wasp-waisted trophic control on the system. An objective-driven frame-based model was constructed to investigate the ability of the approach to represent spatial and population dynamics of sardine and anchovy, and to explore the implications of possible management strategies. Climate variability and fishing pressure were assumed as drivers. Sensitivity analyses were performed and a number of scenarios tested. A frame-based approach appears to be useful within this context. Results suggest that the productivity of the sardine resource within the model is highly dependent on the spatial characteristics of fishing pressure. The role of anchovy within the model system has not yet been fully developed. Increasing our understanding of the relative suitability of environmental conditions of different regions is also important if we are to increase our capacity to predict trends in abundance and distribution. This study shows support for continued careful consideration of spatialized management approaches to the South African sardine fishery.

Improvement in recruitment of Japanese sardine with delays of the spring phytoplankton bloom in the Sea of Japan

AbstractTo evaluate the impact of temporal variation of primary productivity on the recruitment of Japanese sardine (Sardinops melanostictus) in the Sea of Japan, the phenology of sea surface phytoplankton abundance was estimated from 8 day multiple satellite (SeaWiFS, MODIS‐Aqua, MERIS, and VIIRS) derived sea surface chlorophyll (SSChl) a concentrations from January 1998 to December 2015. Because relationships between SSChl a and in situ chlorophyll a concentrations were significantly different among periods based on the satellite combinations used, maximum and minimum SSChl a concentrations of 1 year were relativized as 1 and 0, respectively. Spatio‐temporal variation of relativized SSChl a concentrations was determined by using empirical orthogonal function (EOF) analysis. Scores in the first EOF mode denoted the basin‐scale variations of SSChl a concentrations in the Sea of Japan, and the major peak from the end of February to the end of May displayed the spring bloom. The logarithm of recruitment per spawner (LNRPS) for sardine was positively affected by delays in the start and end dates of the spring phytoplankton bloom. The delay of the date of the lowest sea surface temperature contributed to the delay of the end of the spring bloom during the period 1998–2015 and elevated the LNRPS during the period 1982–2015. Sardine spawns in the southern Sea of Japan from April to May, hence, delays of the spring bloom prolonged its overlap with sardine larval periods, and thus improved the recruitment of Japanese sardine in the Sea of Japan.

Climate change and interspecific interactions drive species alternations between anchovy and sardine in the western North Pacific: Detection of causality by convergent cross mapping

AbstractThe abundance and recruitment of anchovy Engraulis spp. and sardine Sardinops spp. alternate in a synchronized way across the Pacific. Convergent cross mapping (CCM) indicated that climate change drives the alternation of the two species in the California Current System. However, climate indices patterns in the western North Pacific contrast with those in the eastern North Pacific, despite synchronous species alternations occurring. Therefore, it is of great interest to clarify whether climate change, or any other factors, affects the population dynamics of Japanese anchovy and Japanese sardine in the western North Pacific. Using CCM, we tested whether climate change and interspecific interactions affect the population dynamics of these two species. We found that climate change affected recruitment, and we clarified the spatiotemporal pattern of this effect. This result supports the existing hypotheses that population dynamics are regulated by climate change in the western North Pacific. The present study also detected interspecific interactions between sardine and anchovy, which might promote the alternation of the two species, and has not been reported in other regions.

A multi-model approach to understanding the role of Pacific sardine in the California Current food web

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 617-618:307-321 (2019) - DOI: https://doi.org/10.3354/meps12504 A multi-model approach to understanding the role of Pacific sardine in the California Current food web Isaac C. Kaplan1,*, Tessa B. Francis2, André E. Punt3, Laura E. Koehn3, Enrique Curchitser4, Felipe Hurtado-Ferro3, Kelli F. Johnson3, Salvador E. Lluch-Cota5, William J. Sydeman6, Timothy E. Essington3, Nathan Taylor7, Kirstin Holsman8, Alec D. MacCall6, Phillip S. Levin9 1Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA, 2725 Montlake Blvd E, Seattle, WA 98112, USA 2University of Washington Tacoma, Puget Sound Institute, Tacoma, WA 98421, USA 3School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195-5020, USA 4Department of Environmental Sciences, Rutgers University, 14 College Farm Road, Room 243, New Brunswick, NJ 08901, USA 5Centro de Investigaciones Biológicas del Noroeste, S.C., 23096 La Paz, BCS, Mexico 6Farallon Institute, 101 H Street, Suite Q, Petaluma, CA 94952, USA 7Pacific Biological Station, Fisheries and Oceans Canada, 3190 Hammond Bay Rd, Nanaimo, BC V9T 6N7, Canada 8Alaska Fisheries Science Center, NOAA Fisheries, 7600 Sand Point Way NE, Building 4, Seattle, WA 98115, USA 9School of Environmental & Forest Sciences, University of Washington, Box 351200, Seattle, WA 98195, USA *Corresponding author: isaac.kaplan@noaa.govAdvance View available online April 17, 2018 ABSTRACT: We develop a multi-model approach to explore how abundance of a forage fish (Pacific sardine Sardinops sagax) impacts the ecosystem and predators in the California Current, a region where sardine and anchovy Engraulis mordax have recently declined to less than 10% of contemporary peak abundances. We developed or improved applications of 3 ecosystem modeling approaches: Ecopath, Model of Intermediate Complexity for Ecosystem assessment (MICE), and Atlantis. We also used Ecopath diets to predict impacts to predators using a statistical generalization of the dynamic Ecosim model (Predator Response to the Exploitation of Prey [PREP]). Models that included brown pelican Pelecanus occidentalis at the species level (MICE and Ecopath/PREP) both predict moderate to high vulnerability of brown pelicans to low sardine abundance. This vulnerability arises because sardine comprises a large fraction of their diet, and because other important prey (anchovy) also exhibit large population fluctuations. Two of the ecosystem models (MICE and Atlantis) suggest that California sea lions Zalophus californianus exhibit relatively minor responses to sardine depletion, due to having broader diets and lower reliance on another fluctuating species, anchovy. On the other hand, Ecopath/PREP suggests that sardine declines will have a stronger impact on California sea lions. This discrepancy may in part reflect structural differences in the models: Atlantis and MICE explicitly represent density dependence and age-structure, which can mitigate effects of prey depletion in these models. Future work should identify fisheries management strategies that are robust to uncertainties within and among models, rather than relying on single models to assess ecosystem impacts of management and forage fish abundance. KEY WORDS: Forage fish · Pacific sardine · California Current · Ecosystem model · California sea lion · Brown pelican · Multi-model approach Full text in pdf format Supplementary material PreviousNextCite this article as: Kaplan IC, Francis TB, Punt AE, Koehn LE and others (2019) A multi-model approach to understanding the role of Pacific sardine in the California Current food web. Mar Ecol Prog Ser 617-618:307-321. https://doi.org/10.3354/meps12504 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 617-618. Online publication date: May 16, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Comparison of stomach contents between Japanese sardine <i>Sardinops melanostictus</i> and anchovy <i>Engraulis japonicus</i> using commercial fisheries together with the two species in the Japan Sea during spring

Comparison of stomach contents between Japanese sardine <i>Sardinops melanostictus</i> and anchovy <i>Engraulis japonicus</i> using commercial fisheries together with the two species in the Japan Sea during spring

Long-term change in the distribution of Japanese sardine in the Sea of Japan during population fluctuations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 593:141-154 (2018) - DOI: https://doi.org/10.3354/meps12491 Long-term change in the distribution of Japanese sardine in the Sea of Japan during population fluctuations Soyoka Muko1,*, Seiji Ohshimo1, Hiroyuki Kurota1, Tohya Yasuda1, Masa-Aki Fukuwaka1,2 1Seikai National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Nagasaki 851-2213, Japan 2Present address: Hokkaido National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Sapporo 062-0922, Japan *Corresponding author: symuko@gmail.com ABSTRACT: The distribution of small pelagic fish species changes in association with fluctuating stock biomass. We analyzed the spatio-temporal dynamics of Japanese sardine Sardinops melanostictus inhabiting the Sea of Japan during periods of stock biomass fluctuation using generalized additive models (GAMs). Logbook data from drift gill net surveys and large- and medium-type purse seine fisheries, conducted from 1970 to 1999, were used. A 2-step data analysis was performed: (1) for the presence or absence of sardine, and (2) for the catch per unit effort (CPUE) where fish were present. The explanatory variables in the GAMs were year, longitude/latitude, sea surface temperature, and fishing method. The best model based on Akaike’s information criterion showed that the likelihood of high sardine presence was limited to areas around the Oki and Tsushima Islands in the early 1970s. However, these areas expanded south along the coast and offshore to the north until the mid-1980s. Subsequently, sardine presence contracted to the initial distribution areas during the mid-1990s. Over the 30 yr period, the spatial distribution of the CPUE changed minimally for both fishing methods. Compared with the trajectory of stock biomass, the potential distribution area began expanding during the initial phase of population expansion, and started contracting before biomass peaked. There was a time lag between the peaks of distribution area and biomass. In conclusion, we discuss how changes to oceanographic conditions in response to a climate regime shift may influence the distribution of Japanese sardine in the Sea of Japan. KEY WORDS: Japanese sardine · Sardinops melanostictus · Spatio-temporal dynamics · Generalized additive model Full text in pdf format Supplementary material PreviousNextCite this article as: Muko S, Ohshimo S, Kurota H, Yasuda T, Fukuwaka MA (2018) Long-term change in the distribution of Japanese sardine in the Sea of Japan during population fluctuations. Mar Ecol Prog Ser 593:141-154. https://doi.org/10.3354/meps12491 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 593. Online publication date: April 12, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

A probabilistic procedure for estimating an optimal echo-integration threshold using the Expectation-Maximisation algorithm

To obtain reliable fish biomass estimates by acoustic methods, it is essential to filter out the signals from unwanted scatterers (e.g. zooplankton). When acoustic data are collected at more than one frequency, methods that exploit the differences in reflectivity of scatterers can be used to achieve the separation of targets. These methods cannot be applied with historical data nor recent data collected on board fishing vessels employed as scientific platforms, where only one transducer is available. Instead, a volume backscattering strength (Sv) threshold is set to separate fish from plankton, both for echogram visualisation or, more importantly, during echo-integration. While empirical methods exist for selecting a threshold, it often depends on the subjective decision of the user. A−47 dB threshold was empirically established in 2008 at the beginning of a series of surveys conducted by Mexico's National Fisheries Institute to assess the biomass of Pacific sardine in the Gulf of California. Until 2012, when a 120 kHz transducer was installed, only data collected at 38 kHz are available. Here, we propose a probabilistic procedure to estimate an optimalSvthreshold using the Expectation-Maximisation algorithm for fitting a mixture of Gaussian distributions toSvdata sampled from schools associated with small pelagic fish and their surrounding echoes. The optimal threshold is given by the Bayes decision function for classifying anSvvalue in one of the two groups. The procedure was implemented in the R language environment. The optimal threshold found for 38 kHz data was −59.4 dB, more than 12 dB lower than the currently used value. This difference prompts the need to revise the acoustic biomass estimates of small pelagics in the Gulf of California.

Linking knowledge to action in ocean ecosystem management: The Ocean Modeling Forum

The sustainable use of global marine resources depends upon science-based decision processes and systems. Informing decisions with science is challenging for many reasons, including the nature of science and science-based institutions. The complexity of ecosystem-based management often requires the use of models, and model-based advice can be especially difficult to convert into policies or decisions. Here, we suggest five characteristics of model-based information and advice for successfully informing ocean management decision-making, based on the Ocean Modeling Forum framework. Illustrated by examples from two fisheries case studies, Pacific sardines Sardinops sagax and Pacific herring Clupea pallasii, we argue that actionable model-based output should be aspirational, applicable, parsimonious, co-produced, and amplifying.

Coalescent Processes with Skewed Offspring Distributions and Nonequilibrium Demography.

Nonequilibrium demography impacts coalescent genealogies leaving detectable, well-studied signatures of variation. However, similar genomic footprints are also expected under models of large reproductive skew, posing a serious problem when trying to make inference. Furthermore, current approaches consider only one of the two processes at a time, neglecting any genomic signal that could arise from their simultaneous effects, preventing the possibility of jointly inferring parameters relating to both offspring distribution and population history. Here, we develop an extended Moran model with exponential population growth, and demonstrate that the underlying ancestral process converges to a time-inhomogeneous psi-coalescent. However, by applying a nonlinear change of time scale-analogous to the Kingman coalescent-we find that the ancestral process can be rescaled to its time-homogeneous analog, allowing the process to be simulated quickly and efficiently. Furthermore, we derive analytical expressions for the expected site-frequency spectrum under the time-inhomogeneous psi-coalescent, and develop an approximate-likelihood framework for the joint estimation of the coalescent and growth parameters. By means of extensive simulation, we demonstrate that both can be estimated accurately from whole-genome data. In addition, not accounting for demography can lead to serious biases in the inferred coalescent model, with broad implications for genomic studies ranging from ecology to conservation biology. Finally, we use our method to analyze sequence data from Japanese sardine populations, and find evidence of high variation in individual reproductive success, but few signs of a recent demographic expansion.

The True Mechanism That Controls the Stock-Recruitment Relationship

I propose a mechanism that controls the stock-recruitment relationship (SRR), which should replace traditional SRR models. The difference between the traditional SRR models and the model proposed herein is whether or not a density-dependent effect is assumed. The new mechanism elucidates the following: 1) why clockwise loops or anticlockwise loops are commonly observed in an actual SRR, and 2) the age at maturity (not a density-dependent effect) determines the slope of the regression line for the SRR. These cannot be explained by the traditional SRR models, the basis of which is a density-dependent effect. The new SRR mechanism can well explain the SRRs for Pacific stocks of Japanese sardine, Pacific bluefin tuna and Arctic bluefin tuna. The new SRR mechanism proposed herein should be used as a valid SRR model when the management of fishery resources is discussed. Without the adaptation of this new mechanism, fishery resource management may continue to be troubled by the lack of validity of the traditional SRR models.

Meta-analysis of factors associated with omega-3 fatty acid contents of wild fish

Fish are recognized as the main source of physiologically important omega-3 long-chain polyunsaturated fatty acids, namely, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), for human nutrition. However, muscle tissue contents of these fatty acids in diverse fish species, i.e., their nutritive value for humans, varied within two orders of magnitude. We reviewed contents of EPA and DHA, measured by similar methods using an internal standard during chromatography as mg per g of wet mass in 172 fish species belonging to 16 orders, to evaluate probable variations in phylogenetic and ecological drivers. EPA + DHA content varied from 25.6 mg g−1 of wet mass (Sardinops sagax) to 0.12 mg g−1 (Gymnura spp.). Multidimensional redundancy analysis revealed that among phylogenetic, ecomorphological and abiotic environmental factors, the highest proportion of variation contribution belonged to the shared contribution of sets of phylogenetic and ecomorphological factors. Specifically, the highest values of EPA + DHA content were characteristic of fish belonging to the orders Clupeiformes or Salmoniformes, were pelagic fast swimmers, ate zooplankton and inhabited marine waters or migrated from fresh to marine waters (anadromous migrations). High EPA and DHA content in muscle tissues of the above species appeared to be a metabolic adaptation for fast continuous swimming. In contrast to common beliefs, our meta-analysis did not support the significant influence of higher trophic levels (piscivory) and cold environments (homeoviscous adaptation) on EPA and DHA content in fish. However, many causes of high and low levels of physiologically important fatty acids in certain fish species remained unexplained and require evaluation in future studies.

Identifying ecosystem patterns from time series of anchovy (Engraulis ringens) and sardine (Sardinops sagax) landings in northern Chile

ABSTRACTUseful knowledge acquisition from known and systematized information (data) is a big challenge for researchers, users and finally, decision makers. In this sense, knowledge discovery from data (KDD) process represents a valuable tool for information analysis. Moreover, this work presents an approach through KDD in time series pattern identification for anchovy and sardine fisheries and environmental data, in northern Chile. Time series, multivariate analysis and data mining techniques, along with technical literature review for results validation. The KDD approach and the data mining techniques implemented achieved an integration between these variables, identifying relevant patterns associated with fisheries abundance fluctuations and strong association with environmental changes such as El Niño and long-term cold–warm regimes between them, establishing anchovy and sardine pre-dominant time-periods, associated with environmental conditions are identified. The latter establishes groundwork for studying underlying functional relationships that could reduce gaps in the national fisheries management policies for those fisheries.

Influence of environmental variables on the larval stages of anchovy, Engraulis encrasicolus, and sardine, Sardinops sagax, in Algoa Bay, South Africa

We investigated the environmental drivers of larval abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax in Algoa Bay, Eastern Cape (South Africa). This study comprised a pre-drought post-drought time period, comparing the responses of the fish larvae to different factors before and after the drought. The current study presents, for the first time, which environmental variables are affecting the anchovy and sardine larvae populations in the region. Easterly wind speed and zooplankton density were the only environmental variables that presented a significant change between the pre- and post-drought periods, increasing after the drought. Generalized additive models (GAMs) were used in order to explore the effects that environmental factors might have in the abundance of anchovy and sardine larvae in Algoa Bay. Specifically, the GAM that best explained the deviance of the anchovy larvae dynamics included the covariates rainfall, easterly wind speed, Chl a concentration, sardine larvae abundance and the interactions SST*Chla and sard*SST. The GAM best explaining sardine larvae abundance included only the easterly wind speed as a covariate. This model showed that there was a positive relationship between the higher values of wind speed and sardine larvae abundance.

Phenological and distributional shifts in ichthyoplankton associated with recent warming in the northeast Pacific Ocean.

Understanding changes in the migratory and reproductive phenology of fish stocks in relation to climate change is critical for accurate ecosystem-based fisheries management. Relocation and changes in timing of reproduction can have dramatic effects upon the success of fish populations and throughout the food web. During anomalously warm conditions (1-4°C above normal) in the northeast Pacific Ocean during 2015-2016, we documented shifts in timing and spawning location of several pelagic fish stocks based on larval fish samples. Total larval concentrations in the northern California Current (NCC) during winter (January-March) 2015 and 2016 were the highest observed since annual collections first occurred in 1998, primarily due to increased abundances of Engraulis mordax (northern anchovy) and Sardinops sagax (Pacific sardine) larvae, which are normally summer spawning species in this region. Sardinops sagax and Merluccius productus (Pacific hake) exhibited an unprecedented early and northward spawning expansion during 2015-16. In addition, spawning duration was greatly increased for E.mordax, as the presence of larvae was observed throughout the majority of 2015-16, indicating prolonged and nearly continuous spawning of adults throughout the warm period. Larvae from all three of these species have never before been collected in the NCC as early in the year. In addition, other southern species were collected in the NCC during this period. This suggests that the spawning phenology and distribution of several ecologically and commercially important fish species dramatically and rapidly changed in response to the warming conditions occurring in 2014-2016, and could be an indication of future conditions under projected climate change. Changes in spawning timing and poleward migration of fish populations due to warmer ocean conditions or global climate change will negatively impact areas that were historically dependent on these fish, and change the food web structure of the areas that the fish move into with unforeseen consequences.

Multidecadal, centennial, and millennial variability in sardine and anchovy abundances in the western North Pacific and climate–fish linkages during the late Holocene

Paleorecords of pelagic fish abundance could better define the nature of fishery productivity dynamics and help understand responses of pelagic fish stocks to long-term climate changes. We report a high-resolution record of sardine and anchovy scale deposition rates (SDRs) from Beppu Bay, Southwest Japan, showing multidecadal and centennial variability in the abundance of Japanese sardine and Japanese anchovy during the last 2850years. Variations in the sardine SDR showed periodicities at ∼50, ∼100, and ∼300yr, while variations in the anchovy SDR showed periodicities at ∼30 and ∼260yr. Comparisons between and correlation analyses of the time series of the sardine and anchovy SDRs demonstrate that there is not a consistent out-of-phase relationship during the last 2850years. This indicates that the multidecadal alternations in the sardine and anchovy populations commonly seen in the 20th century did not necessarily occur during earlier periods. The Japanese sardine SDR record shows a long-term decreasing trend in the amplitudes of the multidecadal to centennial fluctuations. This decreasing trend may have resulted from an increasing trend in the winter sea surface temperature in the western North Pacific. The multicentennial variability in sardine abundance during the last millennium is consistent with the variabilities in the abnormal snow index in East Asia and the American tree ring-based Pacific Decadal Oscillation index, suggesting a basin-wide or regional climate–marine ecosystem linkage.