Thirty-three water samples from different rivers were collected both in wet period (October December) and in dry period (February April).
The developed methodology has been successfully applied to the analysis of ECDs in sediments from different rivers and lakes of the Lazio Region (Italy).
High-predation females in the laboratory experiment discriminated against low-predation males from the same river (IMI = 0.395), but not against low-predation males from different rivers (IMI = −0.101; Table 1; Fig. 1; Table S3).
Within rivers, sexual selection for orange colour is generally stronger in low- than in high-predation populations [24], [26], [44], [45], however there is substantially more variation in all colour traits among low-predation males from different rivers than high-predation males [20], [25], [26].
It could therefore be argued that observed effects may be a combination of chemical contamination and physio-chemical properties of sediments from different rivers.
As a result, salmonid captive breeding programs are based on the assumption that populations from different rivers, even at fine geographic scales, represent independently evolving 'units' (Fraser 2008) and attempts are made to minimize outbreeding between them.
