Crayfish Corps Resource Brief 2023

A group of volunteers together with park staff use nets to capture and remove invasive rusty crayfish from Valley Creek.

NPS Photo/G. Purifoy

Crayfish Corps is a management action led by Natural Resource staff and supported by volunteers, which aims to limit the effects of invasive non-native crayfish in Valley Creek. Valley Creek, a tributary of the Schuylkill River, is an Exceptional Value Waterway, a Class A wild trout fishery, and is one of the park's most important natural resources.

Objectives of the Crayfish Corps

1. Suppress the rusty crayfish, maintaining a 4:1 ratio of native to rusty crayfish (80% native, 20% rusty) upstream from the dam on Valley Creek

2. Create a meaningful and valuable volunteer opportunity.

(Figure 1) A rusty crayfish.

NPS Photo / G. Purifoy

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Overview

In 2008, the invasive rusty crayfish (Faxonius rusticus) (Figure 1) was first documented in Valley Creek. Rusty crayfish are native to parts of Ohio, Indiana, and Kentucky. They are considered an invasive species because they are bigger, more aggressive, and can out-compete the native crayfish for food and shelter, and they have no natural controls. Additionally, rusty crayfish reduce the amount of aquatic vegetation and insect populations, which ultimately negatively affect large predators in the ecosystem, such as trout.

In locations where rusty crayfish were introduced with no subsequent management action, all other crayfish populations were reduced or eliminated. Because of this, when rusty crayfish were first observed at the Valley Forge, staff established the volunteer “Crayfish Corps” to suppress the invasion of rusty crayfish. For the last fourteen years, park staff, interns, and volunteers have been working on this endeavor.

From May through September, individuals, families, scout troops, school groups, community organizations, and corporate groups have assisted park staff in capturing and removing rusty crayfish from Valley Creek. Valley Creek is divided into four sections within Valley Forge National Historical Park (Figure 2). Each Crayfish Corps event takes place in part of one stream section. Sections are defined by physical barriers like dams and bridges.

(Figure 2) Sections of Valley Creek.

NPS Graphic

Status & Trends: 2009 - 2023

Since Crayfish Corps' inception, 29,160 rusty crayfish have been removed from Valley Creek, and 83,104 native crayfish have been documented and returned to the creek (Figure 3).

Complete eradication of the rusty crayfish is probably not feasible. Therefore, the goal is to maintain a minimum ratio of 4:1 native to rusty crayfish (e.g., 20% or less rusty crayfish) above the dam (sections 2,3, and 4). Over the last six years, this ratio has been achieved consistently in stream sections three and four (Figure 4).

Stream section two did not meet this goal in 2021, but has been under 20% all other years between 2018 and 2023. The average percentage of rusty crayfish caught in section one exceeds 20%. This is attributed to a dam that separates section one and two. The dam is a physical barrier that inhibits rusty crayfish from moving upstream. Section one will continue to be a focus of park staff efforts towards reducing the rusty crayfish population in Valley Creek.

(Figure 3) Number of native and rusty crayfish captured by Crayfish Corps every year.

NPS Graphic

(Figure 4) Average percentage of rusty crayfish captured per creek section since 2018. The black bar shows the goal maintenance level.

NPS Graphic

Because group size, duration, and stream conditions are variable, crayfish data are standardized as the number of crayfish caught per person-hour spent in the stream. This metric helps park staff evaluate the effectiveness of Crayfish Corps over time (Figure 5).

Since its inception in 2009, the number of rusty crayfish caught per person-hour has continually decreased. This, combined with most events above the dam resulting in 20% or less rusty crayfish is very encouraging evidence of the effectiveness of the program.

(Figure 5) Average number of crayfish captured per person hour each year. This includes staff and volunteer hours.

NPS Graphic

The continued success of Crayfish Corps is entirely due to the hard work and enthusiasm of all volunteers involved in the program!

In 2023, Crayfish Corps included 301 volunteers who contributed 636 hours towards rusty crayfish removal. Thank you to all of the wonderful volunteers that helped Crayfish Corp in 2023!

Get Involved

You can contact Natural Resource Management staff to join the Crayfish Corps and find more information about signing up to volunteer at the link below.

Learn how to sign up and see upcoming Crayfish Corps dates

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Natural Resource Management Staff

Kate Jensen

Natural Resource Manager

Marta Lefevre-Levy

Ecologist

Ashley Kroon

Biological Science Technician

This report prepared by:

Theresa Henckel

Community Volunteer Ambassador Intern, 2023-2024.