The Western Fisheries Research Center 

Studies: Threatened and Endangered Fishes

Within historical time, western native fish 

communities have faced increasing threats 

from habitat loss, invasive species, and 

pollution. It should come as no surprise that 

human development has greatly altered fish 

habitat in the west because of the importance 

of water for domestic, agricultural, and 

industrial uses, power generation, waste 

disposal, flood protection, and transportation. 

Fish that were adapted to natural cycles of 

river flow, lake levels, and water temperatures 

have been unable to adapt to the changes to 

these cycles caused by development, leading to 

the listing as threatened or endangered of 68 

species of western native fishes. Rapid 

expansion of non-native fishes, aquatic 

plants, and invertebrates has increased 

competition for food and space while 

pollutants from past and present degrade our 

lakes, streams, and rivers. 

The Western Fisheries Research Center 

(WFRC) and its affiliate field stations and 

laboratories are providing information to the 

Department of the Interior and other 

stakeholders to stop the decline of western 

native fishes. Species with limited 

distributions, such as most desert and arid lands 

fishes, are more likely to be jeopardized than 

fishes with extensive ranges, such as 

anadromous salmon. In fact, many desert 

species have extremely limited distribution 

such as the Devils Hole pupfish (Cyprinodon

diabolis) which is restricted to a small 

depression on the side of a hill, and thus could 

be lost by a single catastrophic event. Some of 

the widespread species such as the Snake River 

stock of fall Chinook salmon (Oncorhynchus 

tshawytscha) face more insidious threats that 

act over time scales of years or decades and 

continuously pressure populations into decline. 

The Devil's Hole pupfish are a short lived 

species of one year or less. The spring 

population varies from 150 to 250, and the 

fall population from 400 to 500. This large 

disparity between spring and fall 

populations is due to severe environmental conditions, low oxygen levels, scant algae-producing sunlight within

the cavern during winter months, and the short lives of these pupfish which 

naturally decline during the winter. They reach a size of only 2.5 cm or less 

because they occur in one of the most restricted habitats (size wise) in the 

world (several square meters).

Society recognized the importance of preventing the extinction of 

species in 1973 with the passage of the Endangered Species Act. 

Sound species recovery science is needed because decisions made 

to halt declines often have very high economic costs. Scientists at 

the WFRC apply many research approaches to the study of causes 

of decline and effects of recovery efforts. Combinations of field 

and laboratory studies coupled with mathematical modeling of 

populations and application of remote sensing technologies are 

used to gather data, analyze trends, determine cause and effect, 

report findings, and help direct recovery. The scientific and 

economic impacts of these studies benefit all segments of society.

U.S. Department of the Interior USGS FS 2006-3064 

U.S. Geological Survey July 6, 2005 
INTERESTING FACTS 

What does ESA mean? 

Endangered Species Act 

Creation of present Endangered 

Species Act: 1973

What does “endangered species” 

mean? 

Any species which is in danger of extinction 

throughout all or a significant portion of its 

range other than a species of the Class 

Insecta determined by the Secretary to 

constitute a pest whose protection under the 

provisions of this Act would present an

overwhelming and overriding risk to man. 

What does “threatened species” mean? 

Any species which is likely to become an 

endangered species within the foreseeable 

future throughout all or a significant portion

of its range. 

How can a species be listed in one 

place and not in another? 

Listings can apply to all individuals of a 

species, only to those in part of their range, or

just to certain genetically-distinct groups. 

For example, the listing of the Whooping

Crane (Grus americana), a native of North 

America, applies to the species throughout its 

range. Sockeye salmon (Oncorhynchus

nerka) occur in areas from Alaska to Idaho, 

but only the genetically-distinct populations

from the Snake River in Idaho and Ozette 

Lake, Washington, are listed as endangered

and threatened, respectively. 

How many species of fish are listed as 

endangered or threatened in the U.S.? 

114 species of fish are listed in the U.S. 

For more information: 

http://www.fws.gov/endangered/

http://www.nmfs.noaa.gov/pr/ 

What is “Critical habitat”? 

"Critical habitat" is defined as areas essential

for the "conservation" of the species in 

question.

"Conservation" is defined as using all means 

necessary to bring a species to the point it no

longer needs the protection of the Act - i.e. 

recovery.

WFRC Studies of Threatened and Endangered Fishes 

Water Quality and Salmonid Population Viability 

compile existing information into

 a format that will allow endangered species recovery planners to consider 

risks posed by various sources and types of water pollution. 

Map of Study Area

Left: Developing testis (with developing

sperm). Right: Developing ovary (with 

developing ova).

In order to fully integrate the 

effects of poor water quality 

on ESA recovery planning it 

is necessary to (1) identify 

locations of known and 

suspected water pollution 

and (2) be able to ascribe 

some level of risk to 

salmonid population viability 

(lethal and sublethal effects) 

when fish are exposed to 

specific compounds (or

mixes of compounds) at any 

life history stage. Sublethal 

effects include reproductive 

abnormalities (see photo) 

caused by a class of 

chemicals that mimic 

estrogens. Our objective is to 

Swimming Performance of Bull Trout (Salvelinus confluentus) 

Bull trout in the western United States are now listed as threatened under 

the ESA. One cause of bull trout population decline is poor fish passage 

around water diversion structures and through road culverts. Scientists 

are measuring the swimming performance of bull trout to help engineers 

design or modify culverts and other fish passage structures in watersheds 

where bull trout are present. 

Response to Water Quality in Upper Klamath Lake, Oregon 

Severe water quality problems in Upper Klamath Lake, Oregon, have led 

to concerns about how Lost River (Deltistes luxatus) and shortnose

suckers (Chasmistes brevirostris) are distributed during the summer and 

whether the suckers can find and use areas with better water quality. 

USGS scientists are using radio telemetry to examining the movements 

and behavior of adult suckers and relating these to water quality in Upper 

Klamath Lake. 

Additional WFRC studies concerning threatened and endangered 

species can be found on the Center’s website at http://wfrc.usgs.gov. 

For additional information, please contact: 

Lyman Thorsteinson, Center Director

U.S. Geological Survey 

Western Fisheries Research Center 

6505 NE 65th Street 

Seattle, WA 98115

Phone: (206) 526-6282 

FAX: (206) 526-6654

http://wfrc.usgs.gov

Female Lost River sucker