Author(s): C. N. Gibbins; H. J. Moir; N. Hakanpaa; H. M. Jackson
Linked Author(s):
Keywords: Invertebrate drift; Salmonid fish; Stream modification; Scotland
Abstract: Juvenile salmonid fish defend small territories and feed primarily on invertebrates drifting downstream in the water column. This study compares patterns of invertebrate drift in a relatively pristine stream and a stream modified to aid agricultural drainage. Invertebrate drift rates in the modified stream were consistently greater than those in the natural stream, despite the numbers of invertebrates on the bed of each stream not being significantly different. This suggests that invertebrates in the modified stream are more prone to drift. As expected, drift rates varied over time, largely in parallel with discharge. However, in both streams, relative drift rates at individual nets were not constant: locations switched from yielding a large biomass of drifting invertebrates to yielding little biomass and vice versa. The implication of this is that relative territory ‘quality' is fluid and, to procure maximum food resources, fish may have to defend different locations at different times.
Year: 2001