Ivlev's Electivity Index

Knowledge graph centered on Ivlev's Electivity Index with 36 nodes and 123 connections. Top connected: aquatic insects, Baetis, Trichoptera, interspecific competition, Baetis bicaudatus.

Method synopsis

Modified gut content analysis method that estimates feeding intensity by counting the proportion of abdominal segments containing food rather than identifying specific prey items.

Synthesized from method descriptions across 2 papers using this protocol.

Procedure from a recent peer-reviewed implementation

Steps below were extracted from the most recent peer-reviewed implementation of this protocol in the corpus — Methods in Stream Ecology (2006). Implementations in other papers (listed below) may differ.

1. Collect invertebrates for electivity analysis
   Use D-frame net, Surber sampler, or Hess sampler to collect macroinvertebrates from prescribed area of substrate including large cobbles in shallow riffle with moderate flow (20-30 cm/s). Alternatively, use electrofishing machine with smaller anode placed inside Hess Sampler for benthic invertebrates.
   Quantities: Goal of collecting at least 100 individuals per sample. Sample areas depend on productivity of stream.Duration: Not specifiedConditions: Shallow (<30 cm) riffle with moderate flow (20-30 cm/s)
   Equipment: D-frame net, Surber sampler, Hess sampler, electrofishing machine
2. Process invertebrate samples for identification
   Place each sample in shallow pan, use forceps to remove and preserve all large predatory stoneflies in jar or whirlpack containing 70% ethanol. Preserve rest of sample after removing large bits of detritus and inorganic sediment. Sort and identify invertebrates to at least family level, especially stoneflies (Baetidae, Leptophlebiidae, Heptageniidae, Ephemerellidae), midges (Chironomidae), and mayflies.
   Quantities: All individuals in sampleDuration: Not specifiedConditions: Laboratory processing
   Equipment: forceps, shallow pan, jars, whirlpacks, 70% ethanol
3. Gut content analysis of predators
   Use two pairs of forceps to pull head from prothorax of most abundant predatory stonefly taxon. Dissect thorax through ventrum and anterior abdomen to extract foregut. Since large predatory stoneflies swallow prey whole, prey should be identifiable if short time has elapsed since predator's last meal. Identify prey fragments by comparison to whole specimens.

Typical Equipment

• dissecting equipment

Output Measurements

• gut fullness proportion

Papers Using This Protocol (2)

Species Studied With This Protocol