Downstream displacement and life-history traits of whitefish,Coregonus lavaretus, in a Norwegian river

Abstract

SynopsisEach year from 1976 to 1985 a part of the freshwater resident whitefish, Coregonus lavaretus, in Liavatn, south-western Norway, was displaced downstreams into the sea. In the sea, they seemed to die within a short period of time. The fish appeared to be flushed downstream by autumn freshets. In age and size, but not sex, the descenders seem representative of the fish in the lake. Females were the predominant sex in the river, whereas the sex ratio did not differ from unity in the lake. Young fish were fast-growing, but the growth rate levelled off at an age of 2 years and an asymptotic length of -30 cm. Males matured mainly at age l+ and females at age 2+. The gonadosomatic index decreased with age, whereas the amount of energy allocated to gonadal tissue relative to somatic tissue increased with age.

Does Early Growth Cause a Phenotypically Plastic Response in Egg Production of Atlantic Salmon?

“…The River Imsa is 1 km long and has a mean annual water discharge of 5.1 m3s-' (Jonsson, Jonsson & Ruud-Hansen 1988). The River Imsa supports a small population of wild anadromous Atlantic Salmon.…”

The relative role of density‐dependent and density‐independent survival in the life cycle of Atlantic salmonSalmo salar

“…The River Imsa, located near the city of Stavanger, south‐western Norway (58°50′N, 6°E), is 1 km long and approximately 10 m wide (total area equals approximately 10 000 m 2 ), and drains Lake Liavatn into the Høgsfjord (32 £ salt). The annual mean water flow in the river is 5·1 m 3 s −1 , with the highest discharge during autumn and winter (mean value: 10 m 3 s −1 ) and the lowest during summer (mean value: 2 m 3 s −1 ; Jonsson, Jonsson & Ruud‐Hansen 1989). The water temperature ranges from about 2 °C in winter to c .…”

“…The water temperature ranges from about 2 °C in winter to c . 20 °C in summer (Jonsson et al . 1989).…”

Migration of landlocked brown trout in two Scandinavian streams as revealed from trap data

“…However, the migration is not only restricted to anadromous salmonids but also a common feature of resident salmonids (e.g., Jonsson et al 1988Jonsson et al , 1989 and several factors has been proposed to promote migration on different scales (review by Gowan et al 1994). However, the migration is not only restricted to anadromous salmonids but also a common feature of resident salmonids (e.g., Jonsson et al 1988Jonsson et al , 1989 and several factors has been proposed to promote migration on different scales (review by Gowan et al 1994).…”