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Density-dependence in space and time: opposite synchronous variations in population distribution and body condition in the Baltic Sea sprat (Sprattus sprattus) over three decades.

Casini M, Rouyer T, Bartolino V, Larson N, Grygiel W - PLoS ONE (2014)

Bottom Line: Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition.We provide evidence that the shift in the spatial distribution of cod, the main predator of sprat, has been the main factor triggering the overall spatial changes in sprat density, and thus condition, during the past thirty years.The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.

View Article: PubMed Central - PubMed

Affiliation: Swedish University of Agricultural Sciences, Department of Aquatic Resources, Institute of Marine Research, Lysekil, Sweden.

ABSTRACT
Spatio-temporal density-dependent processes are crucial regulatory factors for natural populations. However, there is a lack of studies addressing spatial density-dependence in fish growth. A previous investigation has suggested spatio-temporal density-dependence in body condition of Baltic sprat. Here, we used different techniques, such as centre of gravity, distance, and homogeneity indices, to better characterize the spatial and temporal variations in sprat density and body condition in the Baltic Proper. Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition. In the 1980s-early 1990s both centres were located in the middle of the Baltic Proper. From the mid 1990s the centres progressively separated in space, as the sprat population moved towards the north-eastern Baltic Proper, and the centre of maximum condition towards the south-western areas. Moreover, at low abundances, sprat density and condition were homogeneously distributed in space, whereas at high abundances both density and condition showed pronounced geographical gradients. The ecological processes potentially explaining the observed patterns were discussed in the light of the Ideal Free Distribution theory. We provide evidence that the shift in the spatial distribution of cod, the main predator of sprat, has been the main factor triggering the overall spatial changes in sprat density, and thus condition, during the past thirty years. The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.

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Changes in the correlation between the centres of gravity for sprat density and condition.(a) temporal evolution of the correlation between the centres of gravity for density and condition; (b) correlation between the two centres of gravity as function of mean yearly density.
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pone-0092278-g004: Changes in the correlation between the centres of gravity for sprat density and condition.(a) temporal evolution of the correlation between the centres of gravity for density and condition; (b) correlation between the two centres of gravity as function of mean yearly density.

Mentions: The spatial correlation between density and condition decreased over time and became increasingly more negative (Figure 4a). This was further confirmed by the negative association between the time series of spatial correlations and the mean yearly density (Spearman's C = −0.53, p = 0.08) (Figure 4b). The higher the mean yearly density (related to annual total abundance), the stronger was the negative relationship between density and condition over space and the further away were the centres of gravity of density and condition.


Density-dependence in space and time: opposite synchronous variations in population distribution and body condition in the Baltic Sea sprat (Sprattus sprattus) over three decades.

Casini M, Rouyer T, Bartolino V, Larson N, Grygiel W - PLoS ONE (2014)

Changes in the correlation between the centres of gravity for sprat density and condition.(a) temporal evolution of the correlation between the centres of gravity for density and condition; (b) correlation between the two centres of gravity as function of mean yearly density.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3974706&req=5

pone-0092278-g004: Changes in the correlation between the centres of gravity for sprat density and condition.(a) temporal evolution of the correlation between the centres of gravity for density and condition; (b) correlation between the two centres of gravity as function of mean yearly density.
Mentions: The spatial correlation between density and condition decreased over time and became increasingly more negative (Figure 4a). This was further confirmed by the negative association between the time series of spatial correlations and the mean yearly density (Spearman's C = −0.53, p = 0.08) (Figure 4b). The higher the mean yearly density (related to annual total abundance), the stronger was the negative relationship between density and condition over space and the further away were the centres of gravity of density and condition.

Bottom Line: Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition.We provide evidence that the shift in the spatial distribution of cod, the main predator of sprat, has been the main factor triggering the overall spatial changes in sprat density, and thus condition, during the past thirty years.The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.

View Article: PubMed Central - PubMed

Affiliation: Swedish University of Agricultural Sciences, Department of Aquatic Resources, Institute of Marine Research, Lysekil, Sweden.

ABSTRACT
Spatio-temporal density-dependent processes are crucial regulatory factors for natural populations. However, there is a lack of studies addressing spatial density-dependence in fish growth. A previous investigation has suggested spatio-temporal density-dependence in body condition of Baltic sprat. Here, we used different techniques, such as centre of gravity, distance, and homogeneity indices, to better characterize the spatial and temporal variations in sprat density and body condition in the Baltic Proper. Our results evidenced a negative spatio-temporal co-variation between the centres of gravity of density and maximum condition. In the 1980s-early 1990s both centres were located in the middle of the Baltic Proper. From the mid 1990s the centres progressively separated in space, as the sprat population moved towards the north-eastern Baltic Proper, and the centre of maximum condition towards the south-western areas. Moreover, at low abundances, sprat density and condition were homogeneously distributed in space, whereas at high abundances both density and condition showed pronounced geographical gradients. The ecological processes potentially explaining the observed patterns were discussed in the light of the Ideal Free Distribution theory. We provide evidence that the shift in the spatial distribution of cod, the main predator of sprat, has been the main factor triggering the overall spatial changes in sprat density, and thus condition, during the past thirty years. The spatial indices shown here, synthesizing the spatio-temporal patterns of fish distribution, can support the implementation of the EU Marine Strategy Framework Directive.

Show MeSH