Behavioural and physiological response of trout to winter habitat in tailwaters in Wyoming, USA

Abstract

Abstract:Fisheries managers have often suggested that survival of trout during the winter is a major factor affecting population densities in many stream ecosystems in the Rocky Mountains. In Wyoming, trout population reductions from fall to spring in excess of 90% have been documented in some reservoir tailwaters. Though biologists have surmised that these reductions were the result of either mortality or emigration from some river sections, the specific mechanisms have not been defined and the factors leading to the trout loss are unknown. This is a review of four studies that were conducted or funded between 1991 and 1998 by the Wyoming Game and Fish Department to understand the extent of overwinter losses, identify some of the mechanisms leading to those conditions and develop management strategies to help avoid those impacts. Winter studies were conducted on tailwater fisheries in the Green, North Platte, Bighorn and Shoshone rivers to document trout population dynamics, assess physical habitat availability, evaluate trout movement and habitat selection, and understand the relationships between food availability and bioenergetic relationships. Results indicate that winter trout losses are extreme in some years, that trout movement and habitat selection are affected by supercooled flows, and that mortality is probably not directly due to starvation. The combination of physiological impairment with frequently altered habitat availability probably leads to indirect mortality from predators and other factors.

Mid-winter activity and movement of Atlantic salmon parr during ice formation events in a Norwegian regulated river

“…In the study by Roussel et al (2004) 40% of the Atlantic salmon parr disappeared indicating long-distance-movements during the freezing period. Other radio-tracking studies (Brown & Mackay, 1995;Jakober et al, 1998;Annear et al, 2002) have related occurrence of frazil ice with more frequent winter movements of distances longer than 1 km. The data from Orkla River does not concur with these observations.…”

“…Research implies that winter survival is a primary factor affecting fish population dynamics in cold region rivers (Power et al, 1993;Cunjak et al, 1998;Bradford & Higgins, 2001;Annear et al, 2002). As the water temperature drops below 8-10°C juvenile Atlantic salmon change from day activity to predominantly nocturnal behaviour (Fraser et al, 1993;Heggenes et al, 1993;Gries et al, 1997;Cunjak et al, 1998;Hiscock et al, 2002b).…”

Behavioural and physiological responses of brook trout Salvelinus fontinalis to midwinter flow reduction in a small ice-free mountain stream

“…Although there was no detectable effect of flow reductions on energetic condition, increased movement associated with daily flow changes may have increased the vulnerability of S. fontinalis to predation. Mink predation has often been observed to be a major contributor to winter fish mortality of radio‐tagged salmonids (Hiscock et al , 2002; Lindstrom & Hubert, 2004), and the seasonal shift in diel behaviour, characterized by day time concealment (Heggenes & Dokk, 2001; Annear et al , 2002), may be an adaptive behaviour to minimize predation risk (Heggenes et al , 1993; Valdimarsson & Metcalfe, 1998).…”

Factors Affecting Swimming Performance of Fasted Rainbow Trout with Implications of Exhaustive Exercise on Overwinter Mortality

“…Most winter movements are relatively short distances and occur in response to declines in current-reducing cover , Dare et al 2002, Mitro and Zale 2002. Nevertheless, short-term movements over long distances during the winter can be induced by changes in flow (McKinney et al 2001, Annear et al 2002, water temperature (Dare et al 2002), and ice formations (Brown and Mackay 1995, Jakober et al 1998. Depending on availability of habitat, induced movements can occur over several days as fish seek habitats with slower currents (Brown and Mackay 1995, Jakober et al 1998, Sirnpkins et al 2000.…”