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Digitale Medien

Feeding ecology of central Baltic Sea herring and sprat (2004)

Möllmann, C. ; Kornilovs, G. ; Fetter, M. ; [weitere]

Oxford, UK; Malden, USA : Blackwell Science Ltd

Journal of fish biology 65 (2004), S. 0

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ISSN: 1095-8649

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: 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.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00566.x

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A new Retention Index for the Central Baltic Sea: Long-Term Hydrodynamic Modelling Used to Improve Baltic Sprat, Sprattus sprattus, Recruitment Models (2004)

Baumann, H. ; Hinrichsen, Hans-Harald ; Köster, F.-W. ; [weitere]

ICES

In: [Paper] In: ICES Council Meeting 2004, 22.-25.09.2004, Vigo, Spain .

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Publikationsdatum: 2017-01-06

Beschreibung: To study inter-annual differences in drift patterns of larval sprat from the Bornholm Basin, we used a 3D, eddy-resolving circulation model of the Baltic Sea and simulated the drift of Lagrangian particles for each of 24 years (1979-2002) of available forcing data. We observed that in some years particles were transported almost completely out of the basin, whereas circulation in other years retained the majority of drifters within the seeding area (Bornholm Basin). A new retention index was derived that is associated to age 0 sprat recruitment in ICES Subdivision 25, estimated from area-disaggregated MSVPA runs. The significant linear relationship (P〈0.018) between retention index and sprat recruitment explained 24% of the overall variability between 1979-2001. However, the correspondence has not been apparent during the 1980s, when both spawning stock biomasses and recruitment levels were consistently low in the central Baltic Sea. A strong positive coupling of recruitment success to basin retention was only seen during the last decade, characterized by relatively high levels of spawning stock biomass and a tremendous variability in sprat recruitment success. Retention indices corresponding to sprat larvae born late in the year (i.e. June) were much better correlated to recruitment success (R² 〉 80%) than those derived from particles released earlier into the model domain. This intra-annual pattern may suggest that recruitment success in central Baltic sprat was – at least during the last decade - predominantly determined by the relative survival of larval cohorts emerging late in the spawning season. The index is significantly cross-correlated to other environmental time series, most importantly annual surface temperature in August, which makes it difficult to conclude on the processes crucial for central Baltic sprat recruitment success.

Materialart: Conference or Workshop Item , NonPeerReviewed

Format: text

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The marine copepod, Pseudocalanus elongatus, as a mediator between climate variability and fisheries in the central Baltic Sea (2003)

Möllmann, Christian ; Kornilovs, G. ; Fetter, M. ; [weitere]

Wiley

In: Fisheries Oceanography, 12 . pp. 360-368.

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Publikationsdatum: 2019-03-06

Beschreibung: Pseudocalanus elongatus is a key species in the pelagic zone of the deep basins of the Central Baltic Sea. The copepod serves as a major food organism for larval as well as for adult, pelagic planktivorous fish. Large interannual fluctuations in the standing stock of P. elongatus have been attributed to significant changes in the hydrographic environment over the last two decades. In particular, the decreasing salinity in the Baltic deep basins, a result of a change in atmospheric forcing leading to an increase in rainfall since the 1980s and of a lack of pulses of saline water intrusions from the North Sea, was found to affect reproduction and maturation of the copepod. In parallel, dramatic changes in the weight-at-age of herring, one of the most important commercial fishes of the Baltic Sea, have been observed since the late 1980s. Using time-series on herring stomach contents, as well as length and weight, we provide evidence for a chain of events relating variability in climate, salinity and P. elongatus abundance to changes in diet and condition of herring in the Central Baltic Sea.

Materialart: Article , PeerReviewed

Format: text

DOI: 10.1046/j.1365-2419.2003.00257.x

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Resolving the impact of short-term variations in physical processes impacting on the spawning environment of eastern Baltic cod: application of a 3-D hydrodynamic model (2002)

Hinrichsen, Hans-Harald ; St. John, M. ; Lehmann, Andreas ; [weitere]

Elsevier

In: Journal of Marine Systems, 32 (4). pp. 281-294.

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Publikationsdatum: 2017-07-12

Beschreibung: Variations in oxygen conditions below the permanent halocline influence the ecosystem of the Baltic Sea through a number of mechanisms. In this study, we examine the effects of physical forcing on variations in the volume of deep oxygenated water suitable for reproductive success of central Baltic cod. Recent research has identified the importance of inflows of saline and oxygenated North Sea water into the Baltic Sea for the recruitment of Baltic cod. However, other processes have been suggested to modify this reproduction volume including variations in timing and volume of terrestrial runoff, variability of the solubility of oxygen due to variations in sea surface temperature as well as the influence of variations in wind stress. In order to examine the latter three mechanisms, we have performed simulations utilizing the Kiel Baltic Sea model for a period of a weak to moderate inflow of North Sea water into the Baltic, modifying wind stress, freshwater runoff and thermal inputs. The model is started from three-dimensional fields of temperature, salinity and oxygen obtained from a previous model run and forced by realistic atmospheric conditions. Results of this realistic reference run were compared to runs with modified meteorological forcing conditions and river runoff. From these simulations, it is apparent that processes other than major Baltic inflows have the potential to alter the reproduction volume of Baltic cod. Low near-surface air temperatures in the North Sea, the Skagerrak/Kattegat area and in the western Baltic influence the water mass properties (high oxygen solubility). Eastward oriented transports of these well-oxygenated highly saline water masses may have a significant positive impact on the Baltic cod reproduction volume in the Bornholm Basin. Finally, we analysed how large scale and local atmospheric forcing conditions are related to the identified major processes affecting the reproduction volume.

Materialart: Article , PeerReviewed

Format: text

DOI: 10.1016/S0924-7963(02)00040-4

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