Chapter 26 Trophic Relationships of Stream Fishes

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Chapter 26Trophic Relationships of Stream
Fishes

• Matt Ashton
• Stream Ecology
• Department of Biology
• Tennessee Technological University

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Introduction

• Trophic relations begin with foods and feeding
  behavior
• Interactions forge links into food webs
• Position w/in a food web defined by fractional
  trophic level
• Related to size and allometric growth
• Morphological relationships define ecological
  roles w/in webs

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Continued

• Competition vs. predation
• Trophic specialization influences stream
  persistence and ecological composition
• Function at multiple ecological levels throughout
  ontogenetic changes
• Diet analysis as a management strategy and
  ecosystem indicator
• Adaptive radiation suggested by associations
  between food and morphology

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Field Studies

• Place results in the context of ecosystem
• Mesocosms
• Increase power of observational studies
• Diet and Morphology
• Correlates with resource use
• Phenotype expression w/in populations
• Growth and available prey interactions

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Data Collection

• Isolate and reduce measurement error
• Active vs. passive gear
• Stomach contents
• Empty
• Content state

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Gut Content Analysis

• Collect target fish from specific habitats with
  appropriate methods
• Euthanize and preserve specimens and guts
• Process specimens

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Gut Content Analysis

• Obtain contents from GI tracts
• Identify contents
• Quantify contents

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Nondestructive Content Removal

• Passive flushing
• Live release of fish
• Active pumping
• Varied effectiveness
• Large fish

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Assessing Morphological Structures

• Associated with feeding behavior, habitats, and
  prey types
• Measure internal and external features
• Gills
• Mouth orientation
• Intestine lengths

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Advanced Methods

• Morphology of prey
• Pharyngeal teeth

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Data Analyses

• Diet breadth, overlap, diversity, and similarity
• Biotic indicies
• Graphical analyses
• True statistical tests