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

Baumann, H., Hinrichsen, Hans-Harald, Köster, F.-W. and Temming, A. (2004) A new Retention Index for the Central Baltic Sea: Long-Term Hydrodynamic Modelling Used to Improve Baltic Sprat, Sprattus sprattus, Recruitment Models [Paper] In: ICES Council Meeting 2004, 22.-25.09.2004, Vigo, Spain.

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Abstract

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.

Document Type: Conference or Workshop Item (Paper)
Keywords: long-term hydrodynamic modelling, Lagrangian drifters, retention, dispersion, sprat recruitment, central Baltic Sea
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EV Evolutionary Ecology of Marine Fishes
Refereed: No
Date Deposited: 07 Jul 2009 10:03
Last Modified: 06 Jan 2017 13:14
URI: http://eprints.uni-kiel.de/id/eprint/960

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