Relative importance of environmental and spatial variables.

<p>Venn diagrams illustrating the results of variation partitioning on the log-transformed abundance of yellow perch larvae per square meter in the three study years among environmental and spatial variables. The variation explained by environmental and non-directional spatial variables (i.e. MEM and TREND) is represented by circles (grey and open, respectively), whereas plectrum-shaped objects represent the variation explained by directional spatial variables (AEM). Percentage of unexplained variation is given at the bottom right of each panel (Residuals). The sizes of the objects are not proportional to their importance in terms of explained variation.</p

Results of variation partitioning.

<p>Results of variation partitioning on the log-transformed abundances of yellow perch larvae per square meter in the three study years among three spatial scales. Pure directional components are represented by Asymmetric Eigenvector Maps (AEM), whereas pure non-directional ones are represented by Moran Eigenvector Maps (MEM). The linear trend (TREND) is included in the non-directional component at the broad scale. Fractions are expressed as percentages of the total variation, computed from adjusted coefficient of multiple determination (<i>R</i>²_adj). Asterisks indicate pure fractions that are significant at the 0.05 significance level. Results are presented separately by spatial scale. (a) North shore; (b) South shore.</p

Study system and sampling sites.

<p>Lake St. Pierre, St. Lawrence River, Québec, Canada. Filled and open circles represent the locations of the sampling sites in 2005 at the 60–80 cm isobath and at the 80–120 cm isobath, respectively. The inset shows for a subset of sampling sites the general structure of the connection diagram used to build the AEM eigenfunctions. In 2006 and 2007, the sampling sites were located close to the 2005 sites, but adjusted for the water level so that they were located at the pre-determined isobaths. The connection diagram was in some cases adapted to take account of missing data. Arrows indicate the approximate locations of the main known spawning grounds. The main channel of the St. Lawrence River (>10 m deep; dark grey) flows from S-W to N-E. Depth contours are based on averaged water levels in June.</p

Results for the regression models.

<p>Results for the regression model relating the abundance of yellow perch larvae to environmental variables. P model = P-value of the global test of significance; P = P-value for the test of significance of a variable with all the other terms included in the model; <i>R</i>² = explained variation due to the explanatory variable (calculated as the average semi-partial <i>R</i>²); Coeff = regression coefficient. Bold indicates those variables significant at the 0.05 level after controlling for spatial correlation; n.d. = not determined since the global test was not significant.</p><p>Note: The selected variables are ranked following their entry order in the full model (i.e. the model without covariables) during the forward selection procedure. Partial model: model with spatial covariables. Note that forward selection was only applied to build the full model.</p