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Akinori Takasuka – One of the best experts on this subject based on the ideXlab platform.

  • Spawning overlap of Anchovy and sardine in the western North Pacific
    Marine Ecology Progress Series, 2008
    Co-Authors: Akinori Takasuka, Hiroshi Kubota, Yoshioki Oozeki
    Abstract:

    Spatial and temporal spawning overlaps in Japanese Anchovy Engraulis japonicus and sardine Sardinops melanostictus were examined using a long-term data set (1978 to 2004) of monthly egg and larval surveys (total of 102 613 vertical tow samples) off the Pacific coast of Japan. Egg abun- dance was estimated in 15′ latitude × 15′ longitude squares, and spawning area was calculated by summing areas of squares positive for egg occurrence. Both species had offshore expansion (inshore contraction) of spawning grounds with protracted (shortened) spawning periods during high- (low-) biomass phases. Although Anchovy and sardine had different peak spawning periods (April to July and February to March, respectively), their spawnings were coincident from February to June in coastal waters. For Anchovy, annual overlapping spawning area percentages of total spawning area and egg abundances in overlapping areas as percentages of total egg abundances were consistently low (6.4 to 30.6% and 7.2 to 39.9%, respectively). In contrast, for sardine these percentages were con- sistently high and notably increased as population size decreased (21.1 to 80.8% and 1.4 to 86.9%, respectively). Averaged over 5 yr (2000 to 2004), 68.5% of the total area of sardine spawning grounds overlapped with Anchovy spawning grounds, and 61.8% of annual sardine egg abundance was produced in spawning grounds that overlapped with Anchovy. Thus, Japanese sardine population recovery is likely more difficult than Japanese Anchovy population recovery (when interspecific interavtions occur).

  • contrasting spawning temperature optima why are Anchovy and sardine regime shifts synchronous across the north pacific
    Progress in Oceanography, 2008
    Co-Authors: Akinori Takasuka, Yoshioki Oozeki, Hiroshi Kubota, Salvador E Lluchcota
    Abstract:

    Abstract Anchovy and sardine are both abundant small pelagic fish that have exhibited out-of-phase population oscillations in both the western boundary current region off Japan and the eastern boundary current upwelling region off California. These species alternations could indicate approximately synchronous patterns (with some variations in timing between ecosystems) despite the reversed temperature regimes for certain periods across the North Pacific, at least until recently. Here we suggest a contrasting pattern of temperature optima for Anchovy and sardine spawnings between the opposite sides of the North Pacific as a possible mechanism of the synchronous phases of species alternations. Spawning temperature optima were examined for Japanese Anchovy (Engraulis japonicus) and Japanese sardine (Sardinops melanostictus), based on occurrence of eggs and larvae in relation to sea surface temperature. The analyses were based on an updated long-term data set of egg and larval surveys from 1978 to 2004 (102,660 net tows) in the western North Pacific. The ratio of relative frequencies of plankton net samples that are positive for eggs or larvae versus all samples was calculated for temperature intervals of 0.1 °C for both species. This spawning temperature index exceeded 1.0 (baseline for optimum) from ca. 15 to 28 °C with a mid-point at 22 °C for Anchovy and ca. 13–20 °C with a marked peak at 16–17 °C for sardine. Patterns of spawning temperature clearly show “warm” and “eurythermal” Japanese Anchovy and “cool” and “stenothermal” Japanese sardine in the western North Pacific. This relationship between Anchovy and sardine showed a marked contrast to earlier published reports on the spawning temperature optima of northern Anchovy (E. mordax) and California sardine (S. sagax) in the California Current system. The spawning temperature optimum appears to be species-specific rather than genus-specific. The reversed species-specific temperature optima of Anchovy and sardine under the reversed temperature regimes could provide a possible theoretical solution to the synchronous Anchovy and sardine regime shifts across the North Pacific.

  • geographical variations in the trophic ecology of japanese Anchovy engraulis japonicus inferred from carbon and nitrogen stable isotope ratios
    Marine Biology, 2008
    Co-Authors: Hiroshige Tanaka, Akinori Takasuka, Ichiro Aoki, Seiji Ohshimo
    Abstract:

    Carbon and nitrogen stable isotope ratios of Japanese Anchovy (Engraulis japonicus) and their stomach contents were examined and compared among various regions around Japan. Geographical variations in the isotope ratios were found between inshore and Pacific offshore regions. While most of the Anchovy samples had isotope ratios around −17.6‰ for δ13C and 10.0‰ for δ15N as median values, higher (more enriched) isotope values were found in the Anchovy sampled from inshore regions. On the contrary, lower (more depleted) values were found mostly in the Anchovy from the Pacific offshore region including the Kuroshio Extension and Kuroshio-Oyashio transition zones. Higher carbon isotope ratios in the inshore regions may reflect a carbon source from benthic primary producers in addition to phytoplankton possibly through the consumption of the larvae of benthic organisms such as bivalves or decapods, which were found in the stomach contents of the inshore Anchovy. Variations in the nitrogen isotisotope ratio may reflect not only differences in the trophic level of prey species, but also variations in the baseline level of food webs. Stable isotope ratios are potentially a useful tool for understanding the stock/population structure and migration of Anchovy. The present findings indicate the potential importance of the “inshore–offshore” variations in the biology of Japanese Anchovy populations in the northwestern Pacific waters.

Yoshioki Oozeki – One of the best experts on this subject based on the ideXlab platform.

  • Validation of daily increment formation in otoliths of immature and adult Japanese Anchovy Engraulis japonicus
    Fisheries Science, 2010
    Co-Authors: Shigenobu Namiki, Satoshi Katayama, Ichiro Aoki, Hiroshige Tanaka, Osamu Funaki, Yoshioki Oozeki
    Abstract:

    In order to validate daily increment formation in otoliths of immature and adult Japanese Anchovy Engraulis japonicus, three rearing experiments using chemical marking of otoliths were conducted on adult Anchovy in summer 2004 and immature Anchovy in summer 2005 and in winter 2006. In the two experiments conducted in summer, the number of otolith microincrements between alizarin complexone (ALC) marks showed that microincrements were formed daily. In the summer 2005 experiment, immature Anchovy under conditions of reduced daily food rations also showed daily microincrement formation. Average increment width was 0.9 μm in adults and 1.8–3.1 μm in immature Anchovy. In contrast, no clear increments were observed between ALC marks on the otoliths from the experiment in winter 2006, and scanning electron microscope (SEM) observations failed to confirm clear increment formation. We consider that low water temperatures (

  • Spawning overlap of Anchovy and sardine in the western North Pacific
    Marine Ecology Progress Series, 2008
    Co-Authors: Akinori Takasuka, Hiroshi Kubota, Yoshioki Oozeki
    Abstract:

    Spatial and temporal spawning overlaps in Japanese Anchovy Engraulis japonicus and sardine Sardinops melanostictus were examined using a long-term data set (1978 to 2004) of monthly egg and larval surveys (total of 102 613 vertical tow samples) off the Pacific coast of Japan. Egg abun- dance was estimated in 15′ latitude × 15′ longitude squares, and spawning area was calculated by summing areas of squares positive for egg occurrence. Both species had offshore expansion (inshore contraction) of spawning grounds with protracted (shortened) spawning periods during high- (low-) biomass phases. Although Anchovy and sardine had different peak spawning periods (April to July and February to March, respectively), their spawnings were coincident from February to June in coastal waters. For Anchovy, annual overlapping spawning area percentages of total spawning area and egg abundances in overlapping areas as percentages of total egg abundances were consistently low (6.4 to 30.6% and 7.2 to 39.9%, respectively). In contrast, for sardine these percentages were con- sistently high and notably increased as population size decreased (21.1 to 80.8% and 1.4 to 86.9%, respectively). Averaged over 5 yr (2000 to 2004), 68.5% of the total area of sardine spawning grounds overlapped with Anchovy spawning grounds, and 61.8% of annual sardine egg abundance was produced in spawning grounds that overlapped with Anchovy. Thus, Japanese sardine population recovery is likely more difficult than Japanese Anchovy population recovery (when interspecific interavtions occur).

  • contrasting spawning temperature optima why are Anchovy and sardine regime shifts synchronous across the north pacific
    Progress in Oceanography, 2008
    Co-Authors: Akinori Takasuka, Yoshioki Oozeki, Hiroshi Kubota, Salvador E Lluchcota
    Abstract:

    Abstract Anchovy and sardine are both abundant small pelagic fish that have exhibited out-of-phase population oscillations in both the western boundary current region off Japan and the eastern boundary current upwelling region off California. These species alternations could indicate approximately synchronous patterns (with some variations in timing between ecosystems) despite the reversed temperature regimes for certain periods across the North Pacific, at least until recently. Here we suggest a contrasting pattern of temperature optima for Anchovy and sardine spawnings between the opposite sides of the North Pacific as a possible mechanism of the synchronous phases of species alternations. Spawning temperature optima were examined for Japanese Anchovy (Engraulis japonicus) and Japanese sardine (Sardinops melanostictus), based on occurrence of eggs and larvae in relation to sea surface temperature. The analyses were based on an updated long-term data set of egg and larval surveys from 1978 to 2004 (102,660 net tows) in the western North Pacific. The ratio of relative frequencies of plankton net samples that are positive for eggs or larvae versus all samples was calculated for temperature intervals of 0.1 °C for both species. This spawning temperature index exceeded 1.0 (baseline for optimum) from ca. 15 to 28 °C with a mid-point at 22 °C for Anchovy and ca. 13–20 °C with a marked peak at 16–17 °C for sardine. Patterns of spawning temperature clearly show “warm” and “eurythermal” Japanese Anchovy and “cool” and “stenothermal” Japanese sardine in the western North Pacific. This relationship between Anchovy and sardine showed a marked contrast to earlier published reports on the spawning temperature optima of northern Anchovy (E. mordax) and California sardine (S. sagax) in the California Current system. The spawning temperature optimum appears to be species-specific rather than genus-specific. The reversed species-specific temperature optima of Anchovy and sardine under the reversed temperature regimes could provide a possible theoretical solution to the synchronous Anchovy and sardine regime shifts across the North Pacific.

Hiroshi Kubota – One of the best experts on this subject based on the ideXlab platform.

  • Spawning overlap of Anchovy and sardine in the western North Pacific
    Marine Ecology Progress Series, 2008
    Co-Authors: Akinori Takasuka, Hiroshi Kubota, Yoshioki Oozeki
    Abstract:

    Spatial and temporal spawning overlaps in Japanese Anchovy Engraulis japonicus and sardine Sardinops melanostictus were examined using a long-term data set (1978 to 2004) of monthly egg and larval surveys (total of 102 613 vertical tow samples) off the Pacific coast of Japan. Egg abun- dance was estimated in 15′ latitude × 15′ longitude squares, and spawning area was calculated by summing areas of squares positive for egg occurrence. Both species had offshore expansion (inshore contraction) of spawning grounds with protracted (shortened) spawning periods during high- (low-) biomass phases. Although Anchovy and sardine had different peak spawning periods (April to July and February to March, respectively), their spawnings were coincident from February to June in coastal waters. For Anchovy, annual overlapping spawning area percentages of total spawning area and egg abundances in overlapping areas as percentages of total egg abundances were consistently low (6.4 to 30.6% and 7.2 to 39.9%, respectively). In contrast, for sardine these percentages were con- sistently high and notably increased as population size decreased (21.1 to 80.8% and 1.4 to 86.9%, respectively). Averaged over 5 yr (2000 to 2004), 68.5% of the total area of sardine spawning grounds overlapped with Anchovy spawning grounds, and 61.8% of annual sardine egg abundance was produced in spawning grounds that overlapped with Anchovy. Thus, Japanese sardine population recovery is likely more difficult than Japanese Anchovy population recovery (when interspecific interavtions occur).

  • contrasting spawning temperature optima why are Anchovy and sardine regime shifts synchronous across the north pacific
    Progress in Oceanography, 2008
    Co-Authors: Akinori Takasuka, Yoshioki Oozeki, Hiroshi Kubota, Salvador E Lluchcota
    Abstract:

    Abstract Anchovy and sardine are both abundant small pelagic fish that have exhibited out-of-phase population oscillations in both the western boundary current region off Japan and the eastern boundary current upwelling region off California. These species alternations could indicate approximately synchronous patterns (with some variations in timing between ecosystems) despite the reversed temperature regimes for certain periods across the North Pacific, at least until recently. Here we suggest a contrasting pattern of temperature optima for Anchovy and sardine spawnings between the opposite sides of the North Pacific as a possible mechanism of the synchronous phases of species alternations. Spawning temperature optima were examined for Japanese Anchovy (Engraulis japonicus) and Japanese sardine (Sardinops melanostictus), based on occurrence of eggs and larvae in relation to sea surface temperature. The analyses were based on an updated long-term data set of egg and larval surveys from 1978 to 2004 (102,660 net tows) in the western North Pacific. The ratio of relative frequencies of plankton net samples that are positive for eggs or larvae versus all samples was calculated for temperature intervals of 0.1 °C for both species. This spawning temperature index exceeded 1.0 (baseline for optimum) from ca. 15 to 28 °C with a mid-point at 22 °C for Anchovy and ca. 13–20 °C with a marked peak at 16–17 °C for sardine. Patterns of spawning temperature clearly show “warm” and “eurythermal” Japanese Anchovy and “cool” and “stenothermal” Japanese sardine in the western North Pacific. This relationship between Anchovy and sardine showed a marked contrast to earlier published reports on the spawning temperature optima of northern Anchovy (E. mordax) and California sardine (S. sagax) in the California Current system. The spawning temperature optimum appears to be species-specific rather than genus-specific. The reversed species-specific temperature optima of Anchovy and sardine under the reversed temperature regimes could provide a possible theoretical solution to the synchronous Anchovy and sardine regime shifts across the North Pacific.

  • Temperature impacts on reproductive parameters for Japanese Anchovy: Comparison between inshore and offshore waters
    Fisheries Research, 2005
    Co-Authors: Akinori Takasuka, Yoshioki Oozeki, Hiroshi Kubota, Yoshinari Tsuruta, Tetsuichiro Funamoto
    Abstract:

    Abstract Batch fecundity and spawning frequency data for Japanese Anchovy Engraulis japonicus, as well as sea surface temperature (SST) data, derived from the recent literature, were compared between inshore samples (Sagami Bay) and offshore samples (western North Pacific) of Anchovy. The offshore Anchovy were heavier in body weight and had heavier ovaries than the same-size inshore Anchovy. Relative batch fecundity was positively related with gonadosomatic index (GSI) and SST for both the inshore and offshore Anchovy; however, the relationships with GSI and SST differed between these two groups. The relative batch fecundity of the inshore Anchovy rapidly decreased as SST decreased, while that of the offshore Anchovy decreased rather gradually. Although the level of spawning frequency seemed similar between the two groups, the positive relationships to sea temperature differed: the offshore Anchovy would spawn at temperatures ca. 5 °C lower as frequently as would the inshore Anchovy. Comparison of temperature impacts on reproductive parameters suggested the existence of differences between the inshore and offshore Anchovy in their specific spawning ecology.

Mark Dickey-collas – One of the best experts on this subject based on the ideXlab platform.

  • Influence of temperature and food availability on juvenile European Anchovy Engraulis encrasicolus at its northern boundary
    Marine Ecology Progress Series, 2013
    Co-Authors: K Raab, Leopold A. J. Nagelkerke, Adriaan D. Rijnsdorp, Marcos Llope, Lorna R. Teal, Priscilla Licandro, Piet Ruardij, Mark Dickey-collas
    Abstract:

    The European Anchovy Engraulis encrasicolus population of the North Sea has increased and spread in recent decades, probably in response to the relaxation of limiting factors in its life history. We use models and empirical data to explore the effects of temperature and food availability during the first growing season on the adult Anchovy population across the North Sea. First, we compare simulated growth during summer and autumn, from a dynamic energy budget model, with trends in the time series of Anchovy survey catch per unit effort. The proportion of the area of the North Sea in which Anchovy can grow to 10 cm (the potential growth habitat) correlates with the abundance of Anchovy caught in surveys the following year. Second, spatio-temporal statistical modeling is used to show that Anchovy abundance in surveys is related to environmental variables (temperature and food availability). Temperature explains the distribution and abundance of Anchovy in the North Sea better than food availability or a combination of both environmental factors. We conclude that variations in growth during the first months of life can impact Anchovy life cycle closure. Specifically for the North Sea Anchovy, changes in temperature are more important than changes in food availability in allowing the fish to grow to overwintering size, under probably non-food-limited conditions.

  • Anchovy Engraulis encrasicolus diet in the North and Baltic Seas
    Journal of Sea Research, 2011
    Co-Authors: Kristina Raab, Leopold A. J. Nagelkerke, C Boeree, Adriaan D. Rijnsdorp, Axel Temming, Mark Dickey-collas
    Abstract:

    The diet of Anchovy (Engraulis encrasicolus) in the North and Baltic Seas was studied using stomach analysis from four sampling events in different areas. Zooplanktivory was confirmed; the most frequent prey items (in over 40% of stomachs) were copepods, malacostracan larvae and fish larvae. In the Baltic Sea, Paracalanus spp. and Pseudocalanus spp. were important in relative terms; in the German Bight, Temora spp. dominated the stomach contents. Relative abundances of prey items varied with area more than absolute abundance or presence absence of items. Moreover, the level of resolution of prey categories influenced which prey categories were considered to be most important in driving variability in stomach content. Anchovy diet is broad across the seasons, years and areas sampled, suggesting that it is not a specialist feeder in the North Sea. The similarity of diet between Anchovy and other clupeids, as well as Anchovy consumption of larval fish, makes the new increased Anchovy population a potential intraguild predator of commercial species like herring. (C) 2010 Elsevier B.V. All rights reserved

Salvador E Lluchcota – One of the best experts on this subject based on the ideXlab platform.

  • demonstration of a fully coupled end to end model for small pelagic fish using sardine and Anchovy in the california current
    Progress in Oceanography, 2015
    Co-Authors: Kenneth A Rose, Salvador E Lluchcota, Jerome Fiechter, Enrique N Curchitser, Kate Hedstrom, Miguel Bernal, Sean Creekmore, Alan C Haynie, Shinichi Ito, Bernard A Megrey
    Abstract:

    Abstract We describe and document an end-to-end model of Anchovy and sardine population dynamics in the California Current as a proof of principle that such coupled models can be developed and implemented. The end-to-end model is 3-dimensional, time-varying, and multispecies, and consists of four coupled submodels: hydrodynamics, Eulerian nutrient–phytoplanktonzooplankton (NPZ), an individual-based full life cycle Anchovy and sardine submodel, and an agent-based fishing fleet submodel. A predator roughly mimicking albacore was included as individuals that consumed Anchovy and sardine. All submodels were coded within the ROMS open-source community model, and used the same resolution spatial grid and were all solved simultaneously to allow for possible feedbacks among the submodels. We used a super-individual approach and solved the coupled models on a distributed memory parallel computer, both of which created challenging but resolvable bookkeeping challenges. The Anchovy and sardine growth, mortality, reproduction, and movement, and the fishing fleet submodel, were each calibrated using simplified grids before being inserted into the full end-to-end model. An historical simulation of 1959–2008 was performed, and the latter 45 years analyzed. Sea surface height (SSH) and sea surface temperature (SST) for the historical simulation showed strong horizontal gradients and multi-year scale temporal oscillations related to various climate indices (PDO, NPGO), and both showed responses to ENSO variability. Simulated total phytoplankton was lower during strong El Nino events and higher for the strong 1999 La Nina event. The three zooplankton groups generally corresponded to the spatial and temporal variation in simulated total phytoplankton. Simulated biomasses of Anchovy and sardine were within the historical range of observed biomasses but predicted biomasses showed much less inter-annual variation. Anomalies of annual biomasses of Anchovy and sardine showed a switch in the mid-1990s from Anchovy to sardine dominance. Simulated averaged weights- and lengths-at-age did not vary much across decades, and movement patterns showed Anchovy located close to the coast while sardine were more dispersed and farther offshore. Albacore predation on Anchovy and sardine was concentrated near the coast in two pockets near the Monterey Bay area and equatorward of Cape Mendocino. Predation mortality from fishing boats was concentrated where sardine age-1 and older individuals were located close to one of the five ports. We demonstrated that it is feasible to perform multi-decadal simulations of a fully-coupled end-to-end model, and that this can be done for a model that follows individual fish and boats on the same 3-dimensional grid as the hydrodynamics. Our focus here was on proof of principle and our results showed that we solved the major technical, bookkeeping, and computational issues. We discuss the next steps to increase computational speed and to include important biological differences between Anchovy and sardine. In a companion paper (Fiechter et al., 2015), we further analyze the historical simulation in the context of the various hypotheses that have been proposed to explain the sardine and Anchovy cycles.

  • contrasting spawning temperature optima why are Anchovy and sardine regime shifts synchronous across the north pacific
    Progress in Oceanography, 2008
    Co-Authors: Akinori Takasuka, Yoshioki Oozeki, Hiroshi Kubota, Salvador E Lluchcota
    Abstract:

    Abstract Anchovy and sardine are both abundant small pelagic fish that have exhibited out-of-phase population oscillations in both the western boundary current region off Japan and the eastern boundary current upwelling region off California. These species alternations could indicate approximately synchronous patterns (with some variations in timing between ecosystems) despite the reversed temperature regimes for certain periods across the North Pacific, at least until recently. Here we suggest a contrasting pattern of temperature optima for Anchovy and sardine spawnings between the opposite sides of the North Pacific as a possible mechanism of the synchronous phases of species alternations. Spawning temperature optima were examined for Japanese Anchovy (Engraulis japonicus) and Japanese sardine (Sardinops melanostictus), based on occurrence of eggs and larvae in relation to sea surface temperature. The analyses were based on an updated long-term data set of egg and larval surveys from 1978 to 2004 (102,660 net tows) in the western North Pacific. The ratio of relative frequencies of plankton net samples that are positive for eggs or larvae versus all samples was calculated for temperature intervals of 0.1 °C for both species. This spawning temperature index exceeded 1.0 (baseline for optimum) from ca. 15 to 28 °C with a mid-point at 22 °C for Anchovy and ca. 13–20 °C with a marked peak at 16–17 °C for sardine. Patterns of spawning temperature clearly show “warm” and “eurythermal” Japanese Anchovy and “cool” and “stenothermal” Japanese sardine in the western North Pacific. This relationship between Anchovy and sardine showed a marked contrast to earlier published reports on the spawning temperature optima of northern Anchovy (E. mordax) and California sardine (S. sagax) in the California Current system. The spawning temperature optimum appears to be species-specific rather than genus-specific. The reversed species-specific temperature optima of Anchovy and sardine under the reversed temperature regimes could provide a possible theoretical solution to the synchronous Anchovy and sardine regime shifts across the North Pacific.