Differences in Growth Pattern in Two Freshwater Fish Species (Leuciscidae) During Summer Drought in North-West Italy

This study aim is to assess how the water shortage impacted on the growth of two endemic freshwater fish species, the Italian riffle dace Telestes muticellus (Bonaparte, 1837) and Phoxinus spp. complex, in a pre-alpine area in North-West Italy. Both species’ specimens growth depended on the streamflow rate: in particular low water levels weighted on Phoxinus spp. specimens, since they showed a negative growth pattern during dry months, while the Telestes muticellus ones continually had a positive growth pattern in the same time frame. The streamflow rate plays a key role in fish growth during severe drought in this area but mechanisms that allow Telestes muticellus specimens to outcompete Phoxinus spp. ones throughout water shortage periods are still unknown.