Fish Map

Frequently Asked Questions

What is this site? How does it work? allows you to explore fish species by watershed or to see the range of a specific species or genus. Currently the data is limited to the the continental United States and does not include fish species for the watersheds in Hawaii, Alaska, Puerto Rico, or the U.S. Virigin Islands even though the Hydrologic Unit maps for these areas can be found. Currently only native freshwater species are mapped.

Future releases will include watersheds not currently mapped as well as adding saltwater and non-native species.
What is HUC?
Hydrologic Unit Code.
How do I cite
Example: 2015. Fish Distribution Database. Available online at; last accessed September 25, 2015.
For specific species or watersheds the citation is located at the bottom of the page.
Why doesn't Alaska have any fish?
The NatureServe database does not include species information by HUC for Alaska, Hawaii, or the Caribbean regions. If you have any input, please provide it via the contact page.
What are Hydrologic Units?
The United States is divided and sub-divided into successively smaller hydrologic units which are classified into four levels: regions, sub-regions, accounting units, and cataloging units. The hydrologic units are arranged or nexted within each other, from the smallest (cataloging units) to the largest (regions). Each hydrologic unit is identified by a unique hydrologic unit code (HUC) consisting of two to eight digits based on the four levels of classification in the hydrologic unit system.

The fourth level of classification is the cataloging unit, the smallest element in the hierarchy of hydrologic units. A cataloging unit is a geographic area representing part of all of a surface drainage basin, a combination of drainage basins, or a distinct hydrologic feature. These units subdivide the subregions and accounting units into smaller areas. There are 2264 Cataloging Units in the Nation. Cataloging Units sometimes are called "watersheds".

Learn more about Hyrologic Units.
Is my browser supported?
This site has only been tested in the latest versions of Chrome, Firefox, and IE. If you are having issues, please make sure you are using the latest version of your browser. Google Earth plug-in is no longer required as the site has been changed to use only standard Google maps.
Why do some species (e.g. Moxostoma sp. 4) have incomplete scientific names?
These species represent undescribed taxon which basically means that it has been discovered but not formally described.

From Wikipedia - "An undescribed species may be referred to with the genus name, followed by "sp". In some cases, there is more than one undescribed species in a genus. In this case, these are often referred to by a number or letter."

So this example is the fourth undescribed species of the genus Moxostoma. Links

Change Log

  • 09/14/2017 11:15:00
    Fixed an issue preventing users from submitting records. Sorry for the inconvience! Please try again.
  • 08/10/2017 12:45:00
    Added collection data to species maps.
  • 07/31/2017 10:46:00
    User submissions are now online! You can submit your own observations using our new system.
  • 05/26/2017 07:55:00
    Added 2016 collection data from Brian Zimmerman
    Added Mexican data set from Dr. John Lyons
  • 10/25/2016 16:22:00
    Robots have finally defeated me. Adding reCAPTCHA to the contact form. Goodbye spam.
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Data provided by NatureServe.
Database built from NatureServe's Digital Distribution Maps of the Freshwater Fishes of the Conterminous United States, Version 3.0.
Nonindigenous data provided by USGS Nonidigenous Aquatic Species database and NAS Web Services API.
Collection occurence data provided by FishNet 2 API services.