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  • 1
    Electronic Resource
    Electronic Resource
    Feeding ecology of central Baltic Sea herring and sprat (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A unique dataset of stomach contents sampled between 1977 and 1999 in the central Baltic Sea was used to perform a comprehensive study of the feeding ecology of Central Baltic herring Clupea harengus and sprat Sprattus sprattus. Both fish species were mainly preying upon calanoid copepods with Pseudocalanus sp. dominating the diet of herring, whereas sprat generally preferred Temora longicornis. Sprat preyed upon older copepodite stages, indicating size-selective particulate feeding, whereas herring additionally fed on smaller copepodite stages, indicating occasional low food supply inducing filter-feeding. Additional food sources other than copepods were mysids in winter and autumn for medium to large herring, as well as cladocerans for sprat in spring and summer, determined by the seasonal occurrence of these plankton species. Seasonally the highest feeding activity of both fishes species occurred in spring and summer, the main reproductive periods of calanoid copepods. The most important food item for both predators in spring was Pseudocalanus sp. In summer sprat switched to T. longicornis and Acartia spp. Since the late 1970s, the total stomach fullness decreased and the fraction of empty stomachs increased. In parallel the amount of Pseudocalanus sp. in the diets of both fish species decreased. Further, a considerable dietary overlap between both species in spring indicated considerable competition for food resources, especially due to an enlarged sprat stock. The results of this study support the hypothesis that growth reductions observed in Baltic herring and sprat are due to combination of a change in food availability and an increase in density-dependent competition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00566.x
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    Paper (German National Licenses)
    Fulltext
  • 2
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    The spawning grounds and embryonal development of Baltic herring in the Gulf of Riga (2023)
    University of Latvia
    Details
    Publication Date: 2023-11-25
    Description: PhD
    Description: The work was performed at the Latvian Fisheries Research Institute
    Keywords: Baltic herring ; ASFA_2015::S::Spawning grounds ; ASFA_2015::E::Embryonic development ; ASFA_2015::P::Pelagic fish
    Repository Name: AquaDocs
    Type: Thesis/Dissertation
    Format: 40pp.
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    PAPER (OA)
  • 3
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    Multi-level trophic cascades in a heavily exploited open marine ecosystem (2008)
    Royal Society of London
    In:  Proceedings of the Royal Society of London, Series B : Biological Sciences, 275 (1644). pp. 1793-1801.
    Details
    Publication Date: 2019-09-23
    Description: Anthropogenic disturbances intertwined with climatic changes can have a large impact on the upper trophic levels of marine ecosystems, which may cascade down the food web. So far it has been difficult to demonstrate multi-level trophic cascades in pelagic marine environments. Using field data collected during a 33-year period, we show for the first time a four-level community-wide trophic cascade in the open Baltic Sea. The dramatic reduction of the cod (Gadus morhua) population directly affected its main prey, the zooplanktivorous sprat (Sprattus sprattus), and indirectly the summer biomass of zooplankton and phytoplankton (top-down processes). Bottom-up processes and climate–hydrological forces had a weaker influence on sprat and zooplankton, whereas phytoplankton variation was explained solely by top-down mechanisms. Our results suggest that in order to dampen the occasionally harmful algal blooms of the Baltic, effort should be addressed not only to control anthropogenic nutrient inputs but also to preserve structure and functioning of higher trophic levels
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1098/rspb.2007.1752
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Trophic cascades promote threshold-like shifts in pelagic marine ecosystems (2009)
    National Academy of Sciences
    In:  PNAS Proceedings of the National Academy of Sciences of the United States of America, 106 . pp. 197-202.
    Details
    Publication Date: 2016-11-14
    Description: Fisheries can have a large impact on marine ecosystems, because the effects of removing large predatory fish may cascade down the food web. The implications of these cascading processes on system functioning and resilience remain a source of intense scientific debate. By using field data covering a 30-year period, we show for the Baltic Sea that the underlying mechanisms of trophic cascades produced a shift in ecosystem functioning after the collapse of the top predator cod. We identified an ecological threshold, corresponding to a planktivore abundance of ≈17 × 1010 individuals, that separates 2 ecosystem configurations in which zooplankton dynamics are driven by either hydroclimatic forces or predation pressure. Abundances of the planktivore sprat above the threshold decouple zooplankton dynamics from hydrological circumstances. The current strong regulation by sprat of the feeding resources for larval cod may hinder cod recovery and the return of the ecosystem to a prior state. This calls for the inclusion of a food web perspective in management decisions.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1073/pnas.0806649105
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Long term dynamics of main mesozooplankton species in the central Baltic Sea (2000)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 22 . pp. 2015-2038.
    Details
    Publication Date: 2018-05-30
    Description: Long-term dynamics (1959–1997) of the copepod species Pseudocalanus elongatus, Temora longicornis, Acartia spp. and Centropages hamatus, as well as the taxonomic group of cladocerans, are described for the open sea areas of the central Baltic Sea. Differences between areas, i.e. Bornholm Basin, Gdansk Deep and Gotland Basin, as well as between 5 year periods, were investigated by means of Analysis of Variance (ANOVA). No significant differences in mesozooplankton biomass between areas were found. On the other hand, clear time-trends could be demonstrated and related to salinity and temperature, with P.elongatus biomass mainly dependent on salinity and T.longicornis, Acartia spp. and cladocerans biomasses dependent, to a large extent, on thermal conditions. Decreasing salinities since the early 1980s due to a lack of major inflows of highly saline water from the North Sea and increased river run-off, both triggered by meteorological conditions, obviously caused a decrease in biomass of P.elongatus. Contrarily, the standing stocks of the other abundant copepod species and cladocerans followed, to a large degree, the temperature development and showed, in general, an increase. The shift in species composition during this period is considered to be a reason for decreasing growth rates of Baltic herring (Clupea harengus) since the early 1980s, and for sprat (Sprattus sprattus) since the early 1990s. Generally, it is suggested that low mesozooplankton biomasses in the 1990s were caused, at least partially, by amplified predation by clupeid fish stocks.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/plankt/22.11.2015
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Interannual variability in population dynamics of calanoid copepods in the central Baltic Sea (2003)
    ICES
    In:  ICES Marine Science Symposia, 219 . pp. 220-230.
    Details
    Publication Date: 2018-03-20
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Biophysical modelling of larval Baltic cod (Gadus morhua) growth and survival (2002)
    NRC
    In:  Canadian Journal of Fisheries and Aquatic Sciences, 59 . pp. 1858-1873.
    Details
    Publication Date: 2018-05-29
    Description: A coupled hydrodynamic�trophodynamic individual-based model of drift and feeding was utilized to analyze the intra- and inter-annual variability in growth and survival of cod (Gadus morhua) larvae in the central Baltic Sea. Highly temporally and spatially resolved simulated flow fields were used to investigate the potential drift of larval cod from the centre of spawning effort in the Bornholm Basin towards their nursery areas through temporally resolved three-dimensional idealized prey fields. Stomach content analyses of larval cod from the Bornholm Basin revealed calanoid copepod nauplii and early copepodite stages to be the preferred prey organisms. The results of the model runs indicate that larval cod changed from a nonlimited to a food-limited stage because of the strong decrease in abundance of the calanoid copepod Pseudocalanus elongatus during the last two decades. The modeling study revealed retention and dispersal from the main spawning ground to be a key process influencing larval survival. When P. elongatus was available in the prey fields, high cod larval survival rates occurred in spring and early summer. In contrast, when P. elongatus was not available, hatched larvae had only high survival probabilities later in the year or if they were transported into shallower coastal regions.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1139/F02-149
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Long-term trends in abundance of cladocerans in the Central Baltic: the influence of hydrography and predation by fish (2002)
    Springer
    In:  Marine Biology, 141 . pp. 343-352.
    Details
    Publication Date: 2018-06-07
    Description: Long-term dynamics (1960–1997) of the cladoceran species Bosmina coregoni maritima, Evadne nordmanni and Podon spp. are described for the Gdansk Deep and the Gotland Basin (Central Baltic Sea). By using correlation analyses on seasonal time-series, the influence of temperature and salinity on the abundance of cladoceran species was investigated. A clear affinity to higher temperature was found for B. coregoni maritima in summer as well as for E. nordmanni and Podon spp. in spring. In addition to temperature, association tests with salinity revealed besides species-specific preferences, regional and temporal differences. Contrary to B. coregoni maritima, both other species were positively associated to salinity in summer and autumn in the Gdansk Deep. In the Gotland Basin only E. nordmanni was positively correlated to salinity in autumn. Differences in the response to hydrographic variables are possibly stage specific, i.e. between resting eggs and adults, or due to a different adaptation to the abiotic environment.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00227-002-0822-9
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Threshold dynamics in the regulation mechanism of central Baltic Sea zooplankton: causes, mechanisms and ecological implications (2007)
    In:  [Poster] In: 4th International Zooplankton Production Symposium, 01.06, Hiroshima, Japan .
    Details
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
  • 10
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    Discrimination of western Baltic spring-spawning and central Baltic herring (Clupea harengus L.) based on growth vs. natural tag information (2013)
    Oxford University Press
    Details
    Publication Date: 2013-08-22
    Description: Gröhsler, T., Oeberst, R., Schaber, M., Larson, N., and Kornilovs, G. 2013. Discrimination of western Baltic spring-spawning and central Baltic herring ( Clupea harengus L.) based on growth vs. natural tag information. – ICES Journal of Marine Science, 70: 1108–1117. In the Baltic Sea, several stocks of herring ( Clupea harengus L.) are surveyed and managed separately. For assessment purposes, a spatial stock separation based on ICES subdivisions is implemented. However, especially in the western Baltic, the distribution areas of two stocks, the western Baltic spring-spawning herring and the central Baltic herring, overlap. Results of regularly conducted surveys for assessment purposes indicated variable degrees of mixing of both stocks in the survey area, based on conspicuous differences in weights/lengths within certain age groups, especially in an area known for overlapping distribution of both stocks. At present, varying fractions of the central Baltic herring stock have not been taken into account during regular surveys conducted in the western Baltic, leading to possible undetected biases in assessment indices derived from these surveys. Additionally, methods otherwise applied for stock separation of Baltic herring so far are based on parameters that cannot readily be derived during regular surveys. In this paper, we present a simple and quick method to reliably allocate herring to either stock based on a separation function derived from survey-based length-at-age data, thus facilitating a more precise estimate of biomass and abundance indices from regular surveys and commercial fisheries.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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    PAPER CURRENT
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