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

Möllmann, C. ; Kornilovs, G. ; Fetter, M. ; [et al.]

Oxford, UK; Malden, USA : Blackwell Science Ltd

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

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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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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. ; [et al.]

ICES

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

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Publication Date: 2017-01-06

Description: 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.

Type: Conference or Workshop Item , NonPeerReviewed

Format: text

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