Indicator
Acres of "Prime" Fish Habitat
2023 Evaluation
View in Threshold Dashboard

This indicator measures the extent of rocky substrates in Lake Tahoe’s nearshore (i.e., littoral zone) known as “prime” fish habitat. Prime fish habitat is defined as areas that satisfy habitat requirements critical to the distribution of fish or important components of their food chains and life cycles. Regional efforts such as limiting impacts of piers and reducing fine sediment deposit into prime fish habitat aim to improve overall lake habitat. TRPA uses remote sensing methods to determine the amount of prime fish habitat within Lake Tahoe. 

 

Acres Of Prime Fish Habitat - photo by Raja Pal.jpg
Status

Acres of different fish habitat types in Lake Tahoe. Currently, there is more "prime/excellent" fish habitat, which is a combination of spawning (37 acres) and feed-cover habitat (6,095 acres), than required by TRPA. Therefore, the Basin is currently meeting its goals for providing fish habitat in Lake Tahoe.

 

Fish habitat data provided by Spatial Infomatics Group (2015). Access detailed data on Tahoe Open Data. Fish Habitat Feature Class

2023 Evaluation
See how thresholds are evaluated
Status
At or Somewhat Better Than Target
Trend
Little or No Change
Confidence
Moderate
Applicable Standard
F7: A non-degradation standard shall apply to fish habitat in Lake Tahoe. Achieve the equivalent of 5,948 total acres of excellent habitat as indicated by the Prime Fish Habitat GIS Layer as may be amended based on best available science.
Key Points
  • There are 6,135 acres of “prime” fish habitat in Lake Tahoe’s nearshore/littoral zone. The controls in the Regional Plan including the Shoreline Plan adopted in October 2018 prevent degradation of that habitat.
  • Since 1989, TRPA has regulated construction within Lake Tahoe’s littoral zones. TRPA has not permitted the unmitigated construction of piers, boat launches, or other developments that would degrade or disturb the littoral substrate. Projects that impact fish habitat in Lake Tahoe are required by TRPA Code of Ordinances, section 84.11.2, to mitigate impacts at a ratio of 1.5 to 1.
  • A 600 foot no-wake zone is in effect in Lake Tahoe to prevent wave action-driven shoreline erosion that can impair habitat through substrate resuspension. 
  • TRPA and partners developed the Tahoe Boating app to inform boaters about Lake Tahoe, no-wake zone boundaries, area attractions, and how to enjoy the lake safely and responsibly. In addition to preserving fish habitat the no-wake zone keeps boaters, paddlers, and swimmers safe.
  • The standard's focus on physical habitat requirements that may not reflect the status of native fish populations. Recent population surveys in Lake Tahoe show significant declines in native fish species in parts of the nearshore. Declines are likely the result of impacts from the presence of aquatic invasive species in the lake. Control of invasive species remains a high-priority to support native fish populations.
Evaluation Map
Description

Nearshore fish habitat types in Lake Tahoe.

About the Threshold

Prime fish habitat is defined as areas that satisfy habitat requirements critical to the distribution of fish or important components of their food chains and life cycles. This indicator measures the extent of rocky substrates in Lake Tahoe’s nearshore (i.e., littoral zone) known as “prime” or excellent fish habitat. Fish use different diameter rock substrates in Lake Tahoe’s nearshore to satisfy different life history requirements such as spawning, growth, and feeding. Gravel substrates composed primarily of rocks smaller than 64 millimeters and larger than 2 millimeters in diameter are used for spawning by native minnow species, while substrates primarily composed of larger diameter cobble, rocks, and boulders are used for foraging and for cover by a variety of fish species. Marginal habitats are primarily composed of sand and silt substrates that measure less than 2 millimeters in diameter. Spawning, and feed and cover substrates together comprise “prime” or excellent fish habitat according to TRPA.

TRPA’s lake habitat management standard aims to prevent the loss of or disturbance to “prime” fish habitats as a result of shorezone development or other anthropogenic disturbances. This indicator does not measure the abundance of individual fish species, community composition, or trophic structure of Lake Tahoe’s nearshore.

The removal, rearrangement, or covering of littoral zone substrates can influence the status of this indicator. Fluctuations in lake level can also significantly affect the availability of “prime” fish habitat, especially spawning habitat. Urbanization along the shorezone, recreational activities, excessive fish harvest, excessive nutrients, increased water temperature associated with global climate change, and presence of non-native fish and other non-native aquatic plants and animals are all factors that can influence the overall quality of Lake Tahoe’s fish habitat and fish species composition.

Delivering and Measuring Success

EIP Action Priorities

EIP Indicators

Example EIP Projects

Rationale Details
At or Somewhat Better Than Target. Analysis of remotely sensed adn in situ data collected in August 2010 and 2015 estimated that there are about 6,135 acres of “prime” fish habitat in Lake Tahoe’s nearshore/littoral zone, suggesting that the Basin is meeting the adopted management target of 5,948 acres.

The substrate of Lake Tahoe’s shorezone changes slowly through time. Absent human modification or large-scale natural disturbance, lake-wide substance change will likely be observed on the order of decades. TRPA shoreline regulations require disturbances to fish habitat to be mitigated at 1.5 square feet to 1 square foot, and there are no-boat beaching zones to protect spawning habitat. As a result of these policies, and the lack of major natural disturbances in the last four years, no major change is expected.

In 2023, the agency watercraft team spent 1,300 hours on the lake conducting enforcement and educating boaters on environmental protections, which included the issuance of 650 verbal corrective actions, most related to the 600-foot no-wake zone. In addition, the team tagged over 80 illegal moorings.
Little or No Change. Lake Tahoe's fish habitat has been mapped multiple times through a combination of remote sensing and in situ methods and the standard has been found to be in attainment. The policies of the Regional Plan to prevent degradation are consistent with the standard.
Confidence Details
High. High-resolution remotely-sensed imagery was used with state-of-the-art, peer-reviewed methods.
Moderate. Controls on development in the lake prevent modification of fish habitat. The nearshore of the lake is a high-visibility area, where the public regularly reports potential disturbance.
Moderate. If one confidence rating is high and the other is moderate, the overall confidence rating is the lower confidence rating.
Additional Figures and Resources

No photos available.

Use of Remotely Sensed Imagery to Map and Quantify the Extent and Distribution of Lake Tahoe’s Nearshore Substrates and Fish Habitats
Uploaded On
7/31/2024
File Type
PDF
Description
Surface and submerged littoral substrates in Lake Tahoe, CA, NV were mapped from high-resolution satellite imagery using Object-Based Image Analysis (OBIA) analysis techniques. The derived substrate classes were translated into three fish habitats classes (spawning, feed and cover, marginal) in order to evaluate the attainment status with environmental standards related to nearshore fish habitat and to improve map products used for land-use planning and regulatory purposes.