Effect of Changes in Streamflow on the Microhabitat Use and Movements of Sympatric Juvenile Coho Salmon (Oncorhynchus kisutch) and Chinook Salmon (O. tshawytscha) in a Natural Stream

Abstract

The microhabitats at positions selected by juvenile coho (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha) following a change in streamflow differed from microhabitats occupied at normal streamflows. At drought streamflow (37% mean seasonal streamflow (MSF)), juvenile coho salmon selected slower, darker, and higher sites above the streambed (P < 0.05) than sites selected at normal (75% MSF) or flood (159% MSF) flows. Juvenile chinook salmon microhabitat use changed similarly with changes in streamflow, but the differences were not significant. Up to one fifth of the fish chose positions with faster water velocities than those available either 30 cm above or 30 cm lateral to them. These fish chose positions inconsistent with the hypothesis of optimal position selection based on maximizing net energy gain. On average, fish moved 6.8 m following a change in streamflow. Juvenile coho salmon generally moved upstream in response to decreasing streamflows and downstream in response to increasing streamflows. Juvenile chinook salmon tended to move offshore and downstream in response to all streamflow changes. These results show that juvenile coho and chinook salmon will move to find suitable microhabitat following a change in streamflow and that the microhabitats are not the same at all streamflows.

Longitudinal movement of fish in response to a single-day flow pulse

“…Longitudinal displacement of juvenile coho salmon (Oncorhynchus kisutch) has been observed in streams during winter periods when floods are common (Shirvell 1994;Giannico and Healey 1998). However, the presence of complex habitat or coarse substrate may provide shelter to juvenile salmonids and minimize downstream displacement (Heggenes 1988;Bell et al 2001).…”

An analysis of 0+ barbel (Barbus barbus) response to discharge fluctuations in a flume

“…Likewise, in fish behaviour studies, responses to changing flows have often been investigated at the individual level both in laboratory flumes (Valentin et al, 1994;Debowski and Beall, 1995;Bradford, 1997;Huntingford et al, 1999;Vehanen et al, 2000) and in (semi-)natural settings (Pert and Erman, 1994;Shirvell, 1994;Matheney and Rabeni, 1995;Valentin et al, 1996;Armstrong et al, 1998;Bunt et al, 1999;Saltveit et al, 2001;Scruton et al, 2003). Individual-based approaches, therefore, seem to be preferable in flow impact assessment and fish conservation initiatives (Pert and Erman, 1994).…”

Effect of a levee setback on aquatic resources using two-dimensional flow and bioenergetics models

“…However, current mean velocities were generally at or above velocities preferred by juvenile salmonids whereas future mean velocities were within the range of acceptable velocities ( fig. 4) (Raleigh and others, 1986;Shirvell, 1994). An increase in the abundance of low velocity and shallower waters would be expected to have a benefit for juvenile salmonids (Bisson and others, 1988;Shirvell, 1990;Sandercock, 1991;Fausch, 1993).…”