PCA biplots for (A) anchovy (B) sardine (C) North Aegean Sea and (D) Strait of Sicily.

<p>Active variables (spatial indicators) are shown in black. Descriptions of the spatial indicators are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135808#pone.0135808.t001" target="_blank">Table 1</a>. Supplementary variables (biomass and packing density (Pck)) are shown in blue.</p

Summary of the spatial indices (based on [3]) used to characterize the spatial pattern of anchovy and sardine populations.

<p>Summary of the spatial indices (based on [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135808#pone.0135808.ref003" target="_blank">3</a>]) used to characterize the spatial pattern of anchovy and sardine populations.</p

Study areas and sampling design in the Strait of Sicily (A, C) and in the North Aegean Sea (B, D).

<p>Sub-areas are also shown. S1: Adventure Bank, S2: Maltese Bank, G1: Thermaikos Gulf, G2: Thracian Sea</p

Annual maps of sardine density distribution in the North Aegean Sea during summertime.

<p>The position of the centres of gravity and the main spatial patches (contributing >10% to total abundance) are shown. The 200 m isobath is indicated by a continuous line.</p

Annual maps of anchovy density distribution in the Strait of Sicily during summertime.

<p>The position of the centres of gravity and the main spatial patches (contributing > 10% to abundance) are shown. The 200 m isobath is indicated by a continuous line.</p

Observed vs predicted values for multiple regression models of standardized fish biomass on PCA axes scores, per species and area: a) pooled anchovy data from both areas; b) pooled sardine data from both areas; c) pooled anchovy and sardine data from the North Aegean Sea and d) pooled anchovy and sardine data from the Strait of Sicily.

<p>The estimated equation in each case is also shown.</p

Sardine: Box-plots of biomass (t), packing density (Pck) and spatial indicator values per sub-area.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135808#pone.0135808.t001" target="_blank">Table 1</a> for descriptions of abbreviations. S1: Adventure Bank sector in Sicilian waters, S2 Maltese Bank sector in Sicilian waters, G1: Thermaikos Gulf, G2: Thracian Sea.</p

Distribution maps (2006 year) of Chl_sat, POC, CDOM, PAR, UML thickness and BL temperature highlighting the differences in distribution patterns between the two areas.

<p>Black areas correspond to the selected ranges in each area.</p

QI plot related to PCA factor coordinates.

<p>Each plot shows the observed QI curve (solid line), its CI (dashed lines), and the frequency histogram of the considered environmental variable. The dotted line in each plot indicates the value QI = 1. For a correct interpretation factor variables correlation relative to PCA (Tab. 5) must be considered.</p

Anchovy distribution maps in the North Aegean Sea (upper part) and in the Strait of Sicily (lower part).

<p>Symbols size is proportional to the abundance of strictly positive values, while zero values are omitted.</p