Early‐season river entry of adult Atlantic salmon: its dependency on environmental factors

Abstract

River entry of adult Atlantic salmon Salmo salar into the River Tornionjoki, monitored during three migration seasons (1997–1999) by horizontal split‐beam hydroacoustics, started early in June when water temperature was c. 9° C and when the discharge varied between 1700 and 2000 m3 s−1. In 1997 and 1999, migration peaked during the latter half of June, 17 days after the peak flood, at water temperatures ranging from 11· 5 to 18·2° C. Few statistically significant correlations were observed between river entry and six measured environmental factors and those that were significant were not persistent over the years. The strongest correlation ( r = −0·60) was between the number of upstream migrants and seawater level, with a time lag of 1 day in 1998. In 1998 and 1999, no clear diurnal migration pattern was observed, although in 1997 the intensity of midday migration was higher than that of the midnight migration. It is concluded that environmental factors have little effect on river entry of Atlantic salmon in a large pristine river located at high latitude.

A review of the likely effects of climate change on anadromous Atlantic salmonSalmo salarand brown troutSalmo trutta, with particular reference to water temperature and flow

“…For instance, in the River Mistassini, Quebec, Trepanier et al (1996) found that the ascent of landlocked S. salar correlated negatively with water flow, suggesting that the fish preferred falling water phases for ascent. This is supported by findings from north European S. salar (Jensen et al , 1998; Lilja & Romakkaniemi, 2003) and S. trutta rivers (Svendsen et al , 2004). Keefer et al (2004) reported that O. tshawytscha in Columbia River moved more slowly when the water discharge was high.…”

“…Keefer et al (2004) reported that O. tshawytscha in Columbia River moved more slowly when the water discharge was high. Other studies, however, have indicated that the flow has no effect on the upstream migration of adult S. salar (Thorstad & Heggberget, 1998; Lilja & Romakkaniemi, 2003; Thorstad et al , 2003; Karppinen et al , 2004), or S. trutta (Rustadbakken et al , 2004). Salinger & Anderson (2006) maintained that water flow was of minor importance for the migratory speed of the homing O. tshawytscha in the Columbia River.…”

Optimizing sampling effort within a systematic design for estimating abundant escapement of sockeye salmon (Oncorhynchus nerka) in their natal river

“…The lowest daily estimate of 10 000 sockeye per 24-h in our data is low for many Pacific salmon rivers (even within the Fraser River watershed) and it is probably unrealisticly high in the case of Atlantic salmon (e.g., Romakkaniemi et al, 2000;Lilja and Romakkaniemi, 2003). However, the patterns of temporal variation observed in sockeye salmon migration in the Horsefly River in 2005 provide an opportunity to consider alternate sampling designs to the systematic approach currently used.…”

“…migrations in coastal northeast Pacific rivers (e.g., Xie et al, 1997;Daum and Osborne, 1998;Burwen et al, 2005;Enzenhofer et al, 1998) and Atlantic salmon (Salmo salar) in coastal Baltic rivers (Romakkaniemi et al, 2000;Lilja and Romakkaniemi, 2003). These riverine acoustic applications are oriented perpendicular to the water flow, which increases the sample volume while avoiding bottom and surface boundary interference with target detection (Mulligan, 2000).…”

The ‘natural flow paradigm’ and Atlantic salmon—moving from concept to practice

“…Upstream migration of adult salmon has been related to increased discharge, with fish frequently moving on the receding phase of the spate (Alabaster, 1990). Migration has also been shown to occur under medium and low flow conditions (Gowans et al, 1999;Lilja and Romakkaniemi, 2003), and after river entry, fish may even prefer decreasing flow (Trépanier et al, 1996). In regulated rivers with the possibility to control discharge, no relationship between flow and migration was observed when artificial freshets were generated (Thorstad and Heggeberget, 1998).…”