Role of Fish Assemblages in Stream Communities

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Role of Fish Assemblages in Stream Communities
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Measuring Community Structure

• Structure
• Species list
• Relative abundance
• Function
• Ecological guilds
• Combined

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Fish Community Studies

• What is the community?
• How is it composed?
• Previous information
• Temporal and spatial scale

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Defining an Assemblage

• Collect fish
• Identify habitat
• Classify by taxa and function
• Links between environment and classes
• Experimental and quantitative studies
• Model habitat

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Habitat Inventory

• Defines levels of strata for comparison
• Organize into a spatial hierarchy
• Properties emerge when examined at different
  levels
• Provides a context for associations with fish
  assemblages

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How to Inventory?

• High res. aerial photos, topo maps, GIS
• Walk the basin if small
• Group homogenous units
• Hydrological assessment of sample sites
• Collect physical and environmental data

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Visual Estimation

• Snorkeling methods
• Population estimates based on counts
• Quick survey
• Account for factors that affect detection
• Probability of sighting
• Turbidity/visibility
• Interobserver variation

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Mark and Recapture

• Collect
• Mark
• Release
• Resample site in 24-hrs
• Ratio of released fish vs. total fish
• N(M x n)/m

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Depletion Sampling

• 3 passes of similar effort
• Retain fish outside of site after each pass
• Count, ID, measure, weigh, etc.
• CPUE vs. accumulated catch
• Pop. Estimate N from X-intercept

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Evaluating Fish Assemblages

• Taxa abundance, richness, diversity
• Shannon-Weaver index
• Comparing communities
• Jaccards and Morisita-Horn index
• Function defined by morphology
• Feeding, fitness
• Habitat groups
• Classification matrix
• Niche breadth