Kernel density utilisation grids.

<p>Risso’s dolphin: All data (A); August (B); September (C) and Harbour porpoise: All data (D); July (E); August (F); September (G). Densities are presented in percentiles (50; 60; 75; 95%). Sighting locations are indicated by small circles.</p

The estimated effect of environmental covariates on the observed harbour porpoise sighting rate.

<p>Predictions were made by varying the variable of interest (e.g. Lunar cycle in the first figure), but keeping the other values fixed at median values at which they occur in the model data.</p

Overview of different survey sites regarding height, sector coverage (size) and summary of systematic effort (number of 10-min scans) during sea states 0–2 with number of harbour porpoise and Risso’s dolphin sightings relative to corresponding inflection points.

<p>Overview of different survey sites regarding height, sector coverage (size) and summary of systematic effort (number of 10-min scans) during sea states 0–2 with number of harbour porpoise and Risso’s dolphin sightings relative to corresponding inflection points.</p

Forward variable selection based on models fitted to harbour porpoise data, based on the cross-validation log-Likelihood (CVLL).

<p>ΔCVLL is the change in CVLL by adding a (smooth of the) covariate. Sea state and Site entered the model as factor variables. “te(X,Y)” represents a tensor product smooth of X and Y coordinates (Bardsey projection). “s” represents a thin plate regression spline smoother (or cubic regression spline for cyclic smoothers, i.e. for the covariates Lunar cycle, aspect and tidal state). The best model contained all variables up to slope.</p

Forward variable selection based on models fitted to Risso’s Dolphin data.

<p>For more details, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086331#pone-0086331-t002" target="_blank">Table 2</a>. The best model contained all variables up to Aspect.</p

Hours of effort and sighting rates for different tidal states.

<p>HP = Harbour porpoise; RD = Risso’s dolphin.</p

The dominating current speed (m/s) measured for Bardsey Island.

<p>The current speeds for different areas to the West, East and to the North (Bardsey Sound) of Bardsey Island are shown.</p

The estimated effect of environmental covariates on the observed Risso’s dolphins sighting rate.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086331#pone-0086331-g005" target="_blank">Figure 5</a> for more details.</p

The location of Bardsey Island within Cardigan Bay (Wales).

<p>The four different viewing points (A-D) and corresponding survey sectors are also shown.</p