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Using predictive models to estimate effects of flow regulation on net‐spinning caddis larvae in North Swedish rivers
Author(s) -
ENGLUND GÖRAN,
MALMQVIST BJÖRN,
ZHANG YIXIN
Publication year - 1997
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1046/j.1365-2427.1997.00178.x
Subject(s) - abundance (ecology) , species richness , flow (mathematics) , ecology , environmental science , hydropsychidae , biology , larva , mathematics , geometry
1. Effects of flow regulation on abundance and richness of net‐spinning caddis larvae (Hydropsychoidea; Trichoptera) were examined in fifty‐two North Swedish rivers. Models based on conditions at unregulated sites were used to predict densities at impacted sites and the residuals, i.e. the differences between observed and predicted numbers, were used as measures of the effects. 2. Two broad categories of impacted sites were identified. Sites with regulated but unreduced flow often have reduced seasonal flow variation and slightly enhanced short‐term variation, while those with reduced flow usually have long periods of low and stable flow occasionally interrupted by short periods of violently fluctuating flow. 3. The abundance of net‐spinning caddis larvae was significantly lower than predicted at both types of sites (reduction 30%), while richness was significantly reduced only at sites with reduced flow (reduction 20%). 4. A subsequent analysis of the relationship between the effects and variables altered by flow regulations, e.g. flow magnitude and flow variation, indicated that species richness was primarily affected by the occurrence of periods with zero flow, while negative effects of abundance were associated with high flow variability. 5. Significant negative effects on the abundance of individual taxa were observed for Cheumatopsyche lepida and Hydropsyche pellucidula at sites with regulated but unreduced flow. 6. Analyses of the relationships between the effects and regulation‐related variables suggest that H. siltalai was significantly negatively affected by the occurrence of zero flow and that negative effects on Arctopsyche ladogensis were associated with flow reduction and high flow variability.