Transferability of habitat suitability criteria of juvenile Atlantic salmon (Salmo salar)

We constructed generalized habitat criteria for juvenile Atlantic salmon (Salmo salar) based on four river-specific suitability indices for depth, water velocity, and substrate to assess whether habitat criteria for juvenile Atlantic salmon are transferable across rivers. We first tested whether salmon are more likely to occupy higher-quality habitats than generally available in a stream reach based on these composite criteria. We then repeated the same procedure using the river-specific criteria of this study and the generalized habitat suitability criteria of Heggenes. As expected, the river-specific criteria were generally the most effective ones in predicting fish habitat use. However, both of the two generalized criteria also transferred fairly well to the test sites. Viewed across salmon size-classes (<9 cm and >9 cm), the river-specific criteria passed the test in ten of eleven cases (91%), and the two generalized criteria passed in nine (82%) of eleven. Thus, it appears that with respect to summertime habitat criteria for juvenile Atlantic salmon, criteria transference is conceivable at least on a regional scale, and perhaps even on a more universal scale.