Influence of Macroinvertebrate Drift and Light on the Activity and Movement of Colorado River Cutthroat Trout

Abstract

Most studies of the diel pattern of trout foraging have focused on examining gut fullness at different times of the day. We used radiotelemetry coupled with stomach content and macroinvertebrate drift sampling to compare the diel activity of Colorado River cutthroat trout Oncorhynchus clarki pleuriticus with variation of invertebrate drift and light intensity on six dates during summer 1993 in the North Fork Little Snake River, Wyoming. The percentage of trout active was greater during midday than at night (medians, 100% versus 40%) and active fish had fewer transmitter signal strength fluctuations per minute during crepuscular periods than during the remainder of the day (medians, 8.8 versus 12.3). Light intensity and daytime mac roin vertebrate drift rate were significantly correlated with trout activity but 24-h drift rates were not. Stomach samples collected in the afternoon weighed significantly more than samples collected in the morning. Despite declines in daytime drift rate and stream discharge, the diel movement of trout also declined as summer progressed. Drift and diet significantly overlapped on all six dates, but selection occurred for certain taxa, especially terrestrial insects. We believe that Colorado River cutthroat trout in this stream forage primarily during the day in summer and that low light intensities prevented trout from exploiting the nocturnal increase in drifting invertebrates.

Relationship between the drift of macroinvertebrates and the activity of brown trout in a small stream

“…As in the study by Young et al (1997), the bottom of the net was close to the substratum, and the top extended always above the water surface. Immediately after collection, drift samples were identified to taxonomic genera, and individuals of each genus were counted.…”

“…To date, a single, pioneer study has investigated the relationships between the drift of invertebrate prey and the foraging activity of salmonids in natural environments (cutthroat trout Oncorhynchus clarki pleuriticus Richardson; Young et al, 1997). However, it provided little insight into interindividual differences, and did not permit an analysis of individual behaviour with respect to fine-scale temporal variations in the abundance of drift in the activity centre of trout.…”

Ecosystem Services Provided by the Little Things That Run the World

“…Even in systems where invertebrates made up only 10-15% of the terrestrial input, they comprised in total more than a third of the diet [36], which seems to be an indication that stream fish often prey selectively on terrestrial invertebrates falling into the water, e.g., [37].…”

Impacts des coupes forestières sur l'alimentation de l'omble de fontaine (Salvelinus fontinalis) et la structure trophique de lacs en forêt boréale /

“…Many studies have documented the feeding periodicity of brook trout in streams. Some of them indicated that salmonids were dayactive (Walsh et al 1988, Young et al 1997 while others considered brook trout as an efficient night predator (Gries et al 1997). Others associate brook trout with a feeding at twilight (Clark and Levy 1988, Sirois and Boisclair 1995, Kreivi et al 1999.…”