Skip to main content
U.S. flag

An official website of the United States government

Here’s how you know

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

HTTPS

Secure .gov websites use HTTPS
A lock (LockA locked padlock) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

    • Environmental Topics
    • Air
    • Bed Bugs
    • Chemicals and Toxics
    • Climate Change
    • Emergency Response
    • Environmental Information by Location
    • Environmental Justice
    • Greener Living
    • Health
    • Land, Waste, and Cleanup
    • Lead
    • Mold
    • Pesticides
    • Radon
    • Science Topics
    • Water Topics
    • A-Z Topic Index
    • Laws & Regulations
    • By Business Sector
    • By Topic
    • Compliance
    • Enforcement
    • Guidance
    • Laws and Executive Orders
    • Regulations
    • Report a Violation
    • Environmental Violations
    • Fraud, Waste or Abuse
    • About EPA
    • Our Mission and What We Do
    • EPA Administrator
    • Headquarters Offices
    • Regional Offices
    • Labs and Research Centers
    • Planning, Budget, and Results
    • Organization Chart
    • EPA History
    • Staff Directory
National Aquatic Resource Surveys
Contact Us

Indicators: Fish Assemblage

What is fish assemblage?

Fish assemblage refers to the variety and abundance of fish species in a given waterbody.

Why is it important to evaluate fish assemblage?

fish in a net
Orangespotted sunfish, Maumee River, Ohio. Photo: Mimi Soo-Hoo

Fish are sensitive indicators of physical and chemical habitat degradation, environmental contamination, migration barriers and overall ecosystem productivity. They require plants, insects and small aquatic creatures to feed on; in-stream and streambank cover to shelter in; appropriate sediment/substrate conditions for spawning; and overhanging vegetation to shade the water in which they live. They are affected by changes in temperature, dissolved oxygen, pH and myriad other physical and chemical constituents in water. They are also long-lived, will move (if they can) to avoid pollutants or other stresses and are economically, culturally and recreationally valuable.

What can fish assemblage tell us about the condition of water?

Evaluating fish assemblage has been integral to water monitoring and water quality management programs for many years. Because of the roles fish play in aquatic communities, and their ability to move to different environments based on changing conditions, the variety and diversity of fish species found at a given site serves as an indicator of biological integrity and water quality.

  • National Aquatic Resource Surveys Home
  • Background
    • Indicators
    • Manuals
    • Map of Sampled Sites
  • NARS Data
    • Journal Articles
    • Applying the Data
    • Related Studies and Tools
  • National Coastal Condition Assessment
  • National Lakes Assessment
  • National Rivers and Streams Assessment
  • National Wetland Condition Assessment
  • Outreach Materials
Contact Us to ask a question, provide feedback, or report a problem.
Last updated on May 26, 2023
United States Environmental Protection Agency

Discover.

  • Accessibility Statement
  • Budget & Performance
  • Contracting
  • EPA www Web Snapshot
  • Grants
  • No FEAR Act Data
  • Plain Writing
  • Privacy
  • Privacy and Security Notice

Connect.

  • Data.gov
  • Inspector General
  • Jobs
  • Newsroom
  • Open Government
  • Regulations.gov
  • Subscribe
  • USA.gov
  • White House

Ask.

  • Contact EPA
  • EPA Disclaimers
  • Hotlines
  • FOIA Requests
  • Frequent Questions

Follow.