Squalius carolitertii

Squalius carolitertii, the Northern Iberian chub, is a species of fresh-water fish in the family Cyprinidae. It is found in Portugal and Spain, and known there as the bordallo, escalo or gallego.

Its natural habitats are rivers and intermittent rivers. It is not considered threatened by the IUCN.

Distribution
Squalius carolitertii is a small endemic cyprinid inhabiting the rivers of the Iberian Peninsula across a large area, including the Douro, Mondego, Lima, Minho, and Lérez basins. Recently several researchers have reported this species for the first time from the upper reaches of the Alberche River (a tributary of the Tagus basin in central Spain) and in the Oitavén River (a tributary of the Verdugo River in northwestern Spain).

Diet
S. carolitertii is an omnivorous fish feeding predominantly on aquatic invertebrates, being nymphs of Baetis spp. The most abundant prey, although detritus, is an important food item. Moreover, in S. carolitertii, as in many other fish species, there is normally a change in the diet composition during the life of the fish, and these age-related diet shifts occur at three different levels: (1) frequency of occurrence of detritus decreases with fish age; (2) prey selection varies with fish age; and (3) mean prey size increases as fish size increased.