Supporting Measures

Additional measures to accomplish the goals of the Edwards Aquifer Habitat Conservation Plan

Net Disturbance & Incidental Take

Overview

The Incidental Take Permit (ITP) issued to the Edwards Aquifer Recovery Implementation Program by the U.S. Fish & Wildlife Service authorizes “take” of certain species (“Covered Species”) resulting from aquifer groundwater pumping and recreational and other activities in the Comal and San Marcos springs and river systems.

This “take” is authorized with the provision that a habitat conservation plan to protect the Covered Species is implemented—hence, the Edwards Aquifer Habitat Conservation Plan (EAHCP). The accurate and timely measurement of take—broadly defined as “anything that disrupts the routine activities of the Covered Species”—is fundamental to compliance with the ITP.

This page provides definitions for terminology associated with take, followed by an illustrative overview of how take is calculated for one of the EAHCP’s Covered Species. Each of the Incidental Take/Net Disturbance Assessments conducted to date in support of the EAHCP can be accessed below.

The table above shows HCP take measured since the program began.

Annual Assessments

A darter gives its best “disturbed” face. The take provision is implemented to provide protection for threatened and endangered species. Even momentarily disturbing, without physically harming, a Covered Species can be considered an example of “take.” Photo credit Lisa Powers, 2015.


"Take" Terminology

Take
Section 3(18) of the Federal Endangered Species Act defines “take” as an activity that will harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or the attempt to engage in any such conduct.

  • “Harass” is further defined as an intentional or negligent act or omission that creates the likelihood of injury to a listed species by annoying it to the point as to significantly disrupt normal behavioral patterns (breeding, feeding and sheltering).
  • “Harm” is further defined to include significant habitat modification or degradation that results in injury or death to listed species by impairing normal behavioral patterns.

Broadly speaking, if you do anything (intentionally or unintentionally) that disrupts the routine activities of a Covered Species, you have committed a “take” of that species.

Incidental Take
Take that results from, but is not the purpose of, an otherwise lawful activity.

Incidental Take Permit (ITP)
This is a specific permit issued under Section 10 of the Federal Endangered Species Act to private parties that are conducting otherwise lawful activities that might result in the taking of an endangered or threatened species.  An ITP will have specific requirements, including (but not limited to) the preparation and implementation of a "Habitat Conservation Plan" (HCP).

EAHCP Covered Species
Species covered by the EAHCP are listed by the U.S. Fish & Wildlife Service (USFWS) as endangered or threatened, or have been included in the event that they are listed.  The species that are authorized for incidental take in the ITP are:

  • fountain darter
  • Comal Springs riffle beetle
  • Comal Springs dryopid beetle
  • Peck’s cave amphipod
  • Texas blind salamander
  • San Marcos salamander

Although the Texas cave diving beetle, Texas troglobitic water slater, and Comal Springs salamander are listed in the ITP, take does not apply, since none of these species are federally listed at this time.  Take assessments for the San Marcos gambusia (presumed to be extinct) will apply if they are found in the study area. Since Texas wild-rice is a plant, it does not receive incidental take coverage under federal permits.

Total Occupied Habitat
This is the total area within the project area that has been historically documented as occupied by the listed species. It will vary by species, and their occupied habitats may overlap.

Occupied Habitat Disturbed
This is the all project areas disturbed by EAHCP activities that overlay the baseline occupied habitat for a given Covered Species per system.  It will vary by species, and their occupied habitats may overlap.


Calculating Take Under the ITP

First, determine the total occupied habitat (submerged aquatic vegetation, spring orifice, etc.) for each species.  Next, the occupied habitat disturbed by the two categories of take has to be determined and overlain on the total occupied habitat to determine the “footprint” of the EAHCP covered activities. 

The two categories of incidental take specific to the EAHCP are:

1. Direct HCP mitigation and restoration - The incidental take associated with EAHCP designed and implemented mitigation and restoration activities.  Per the ITP, it is limited to no more than 10% of the occupied habitat on an annual basis when implementing restoration that may directly or indirectly affect the listed species.

2. All other HCP measures - The incidental take associated with implementation of all the other EAHCP measures (incorporating drought), to the degree practical. 

Once the occupied habitat and the range of disturbance for each species has been determined for the two categories, the percentage of occupied habitat disturbed can be calculated. This calculation simply represents the amount of occupied habitat that was disturbed, which is a necessary part of the incidental take equation, but not incidental take.  Following this, long-term collection data on the covered species and their occupied habitat is used to develop density (individuals/m2) descriptive statistics (percentiles, median, & mean) to use in the formal calculation of incidental take. If the 25th-percentile density of species density is determined as the appropriate metric per established criteria in the methodology, this number is then multiplied by the species specific disturbed occupied habitat to determine the incidental take for both categories.  The incidental take for each category is reported in the ITP separately and combined as an overall total.

An ecologist wades through the Comal River to monitor fountain darter populations. The take provision is implemented to provide protection for threatened and endangered species. Even momentarily disturbing, without  physically harming, a Covered Species can be considered an example of “take.”


Conclusion

Performing the incidental take/net disturbance assessment—collecting data and making calculations to account for the impacts on the Comal and San Marcos spring and river systems that occur in the course of a year, over a broad spatial extent, and through different habitat types for a diverse array of taxa—is an inherently complex task. For additional detail on the intricacies involved in these assessments and associated calculations, those interested can refer to the full memoranda provided at the top of this page. As a requirement under the ITP, these assessments are reviewed annually by the U.S. Fish & Wildlife Service via the EAHCP’s annual report to ensure permit compliance.

© 2017 Edwards Aquifer Authority