The functional relationship between peak spring floods and survival and growth of juvenile Atlantic Salmon (Salmo salar) and Brown Trout (Salmo trutta)
Aj. Jensen et Bo. Johnsen, The functional relationship between peak spring floods and survival and growth of juvenile Atlantic Salmon (Salmo salar) and Brown Trout (Salmo trutta), FUNCT ECOL, 13(6), 1999, pp. 778-785
1. The effects of high spring floods on survival and growth of juvenile Atl
antic Salmon, Salmo salar, and Brown Trout, Salmo trutta, are explored, usi
ng data from a long-term study in the River Saltdalselv, northern Norway. T
he flow regime in this river is typical for northern rivers.
2. There was considerable variation in year class strength of both species.
3. Mortality of Atlantic Salmon increased significantly in years with high
discharge during the alevin stage as well as the first week after emergence
. High discharge during the egg stage and more than 1 week after emergence
seemed to be of minor importance. Water temperature at emergence was rather
high (average 10.5 degrees C) and did not significantly affect year class
strength.
4. Brown Trout emerged earlier than Atlantic Salmon at an average water tem
perature of 8.2 degrees C. Highest mortality was observed in years with low
water temperatures at emergence as well as high discharge during the alevi
n stage.
5. For 1-year-old fish or older, the size of the spring peak flood did not
influence mortality significantly.
6. Growth of Atlantic Salmon parr was diminished in years with a high peak
spring flood. A similar effect on Brown Trout was not detected.