Potential Impacts of Invasive Crayfish on Native Piedmont Crayfish

(Cambarus sp. C) - Insights from Laboratory Experiments

James Wilson, Patricia Hale, Bryan Ditursi, Jackson Wagstaff, & Sujan Henkanaththegedara

Department of Biological & Environmental Sciences, Longwood University, Farmville VA.

INTRODUCTIONInvasive species are identified as the second greatest cause for imperilment

of native species in the United States (Wilcove et. al., 1998).

In Virginia, there are 137 known invasive taxa, including 3 invasive crayfish

species. Also there are about 50 native crayfish species (VDGIF 2014).

Invasive crayfish can dramatically alter shallow water habitats and cause

population declines of native species via predation, competition and

hybridization (Guiaus & Dunham, 1999; Marther & Stein, 1993).

Research Objectives

Assess the potential impacts of invasive Virile crayfish (Orconectes virilis) on

native Piedmont crayfish (Cambarus sp. C).

1. Agnostic behavior (i.e. Aggression assays)

2. Interspecific competition for food (i.e. Feeding assays)

3. Survival in sympatry

2. Interspecific Competition for Food (Feeding Assays)

• The same crayfish pairs (N=13) were used for feeding assays.

3. Survival in Sympatry

• Individual survival of crayfish in 8L tanks were monitored for 120 hours in 8

hour intervals (N=13).

• Kaplan–Meier estimates of proportional survival for both crayfish species

were estimated using Survival Analysis.

REFERENCESGuiaus, R.C. and D.W. Dunham. 1999. Interactions between the Crayfishes Cambarus bartonii and C. robustus: Interspecific and Intraspecific Contests. Journal of

Crustacean Biology 19:131-146.

Karavanich, C. and J. Atema. 1998. Individual recognition and memory in lobster dominance. Animal Behavior 56: 1553-1560.

Marther, M.E. and R.A. Stein. 1993. Direct and Indirect Effects of Fish Predation on the Replacement of a Native Crayfish by an Invading Congener. Canadian

Journal of Fisheries and Aquatic Sciences 50: 1279-1288

Wilcove, D.S., D. Rothstein, J. Dubow, A. Phillips, and E. Losos. 1998. Quantifying Threats to Imperiled Species in the United States. Bioscience 48: 607-615

ACKNOWLEDGEMENTSWe thank Dr. Zachary Loughman at West Liberty University for his help with crayfish field collection; Johnny Leder, Eric

Salamon and Samuel Hull for assistance in setting up the experiments and crayfish care; VAS Small Project research

grant, the Department of Biological & Environmental Sciences and Longwood University Perspectives on Research In

Mathematics & Science (LU-PRISM) for research funding.

RESULTS

RESEARCH PLAN

Figure 1. Study species; (A) Invasive Virile crayfish (Orconectes virilis), and (B)

Native Piedmont crayfish (Cambarus sp. C).

(A) (B)

Figure 2. A flow-through system with 30, 8-L tanks were used as experimental units.

Native and invasive crayfish pairs were housed in individual tanks for up to 120 hours to

study interspecific interactions.

1. Agnostic Behavior (i.e. Aggression Assays)

Figure 3. Native Cambarus sp. C and

invasive Orconectes virilis were not

significantly different in carapace length (N

= 13; W = 112, p = 0.166) and left claw

length (N = 13; W = 110.5, p = 0.1908).

RESULTS

3. Survival in Sympatry

Figure 6. The overall survival of native Cambarus sp. C dropped by 62% over a 120-hour

period due to predation by invasive Orconectes virilis (Χ2 = 4.66; d.f. = 1; P = 0.0309).

Solid lines indicate Kaplan–Meier proportional survival function, and dashed lines indicate

95% confidence intervals.

CONCLUSIONSAggression assays suggested that invasive virile crayfish tend to be more

aggressive towards native Piedmont crayfish.

Feeding assays suggested that invasive virile crayfish could detect food more

quickly than native Piedmont crayfish and “win” the competition for food.

Sympatric survival trials also suggested that there is a negative impact of

the presence of invasive virile crayfish on survival of native Piedmont crayfish.

Overall, invasive virile crayfish could pose a significant threat to the

existence of native Piedmont crayfish.

ABSTRACTInvasive species are identified as the second greatest cause for imperilment of native species in

the United State. In Virginia, there are 137 known invasive taxa, including three invasive crayfish

species, and about 50 species of native crayfish. Invasive crayfish can dramatically alter shallow

water habitats and cause population declines of native species. We assessed the potential

impacts of invasive virile crayfish (Orconectes virilis) on native Piedmont crayfish (Cambarus sp.

C) using a series of laboratory experiments. We have focused on interspecific 1) Aggressive

behavior, 2) Competition for food, and 3) Survival in sympatry. Native Cambarus sp. C and

invasive O. virilis were not significantly different in body size. However, invasive O. virilis showed

more agnostic behavior compared to native Cambarus sp. C (W = 110.5, p = 0.1908). Majority

(85%) of invasive O. virilis reached food faster (W = 48, p = 0.0594) and spent more time feeding

(W = 113, p = 0.1425; A & B) making more of them (62%) “winners” (C) compared to native

Cambarus sp. C. The overall survival of native Cambarus sp. C dropped by 62% over a 120-hour

period due to predation by invasive O. virilis (Χ2 = 4.66; d.f. = 1; P = 0.0309). Overall, invasive

virile crayfish (O. virilis) could pose a significant threat to the existence of native Piedmont

crayfish (Cambarus sp. C).

RESEARCH PLAN1. Agnostic Behavior (i.e. Aggression Assays)

• Crayfish were acclimated in individual 4L tanks for at least two weeks including a 48 hour starvation period (Guiaus & Dunham, 1999).

• Native and invasive crayfish were paired (N=13) based on carapace length (