River roaches: The Quest to Better Understand Crayfish

by Michael Moore, guest blogger

Some call them yabbis, mudbugs or spoondogs. But most of you know them by a different name: crayfish.  My scientific introduction to crayfish was by another name–“ the cockroaches of the creek; they eat everything and everything eats them!”This was the answer I received when asking a scientist about crayfish.

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We think of crayfish as small but some species can grow quite large to the point where they resemble lobsters. This species which is the largest freshwater invertebrate in the world is found on the island of Tasmania off the coast of Australia. Source.

Comparing something to a creepy crawly household pest might not be the best metaphor for encouraging conservation, but I took the analogy as it was intended– an accolade for this unsung hero of aquatic ecosystems. Crayfish are abundant and adaptable to different habitats and food sources. This allows them to function as a strong lynch pin in ecosystems around the world.

Crayfish are important. Many crayfish are specialists. Some are restricted only to flowing waters. Some are totally blind and live only in caves. Others can live in nearly any aquatic habitat imaginable, and create habitats for other species. Throughout their distribution, crayfish serve as the “middle link” in many ecosystems—they are both predators of invertebrates and prey to many important gamefish. At the same time, some crayfish are the most destructive invasive species imaginable. Regardless of their ecological role, the world would be a much different place without crayfish.

crayfish3

Fish sure love crayfish. They are the preferred prey of many game species such as the Smallmouth Bass. Source.

Crayfish are diverse. North America boasts the highest crayfish diversity in the world: over 350 species…and the list keeps growing! Legend has it that roaches can survive even nuclear explosions, but most crayfish species are much more vulnerable. They are threatened by the same factors that affect fish and mussels: pollution, sedimentation, invasive species and disease. Despite the threats to crayfish, only four species are currently recognized under the Endangered Species Act, although many more probably deserve protection.

We still know very little about crayfish. Many important questions about crayfish focus on taxonomy and life history (diet, growth rate, number of offspring, etc…). These details are critical to conservation and management, but are often overlooked by scientists. In fact, only about 12% of crayfish species have published life history studies. The disparity in research on crayfish limits our ability to effectively manage these important organisms.

crayfish1

Crayfish are good parents too! Females carry their eggs and young attached to swimmerets on the underside of their telson (tail). Source.

How come? Unfortunately, life history studies are often deemed old-fashioned in the fast-paced environment of scientific research. Today, scientists’ worth is judged by how many articles they publish in high-impact journals, and how many times those papers are cited. We are desperately in need of updated range maps and reliable identification keys for crayfish throughout the world. However, scientists have few incentives to conduct basic ecological studies on crayfish. In an ideal world, researchers would not be penalized for conducting “less flashy” basic ecological research. But entrenched values of the scientific system are unlikely to change anytime soon. On the bright side, likely future listings of species under the Endangered Species Act will increase funding opportunities for this research on rare crayfish.

The biggest downfall of basic science can be turned into its greatest asset. In many cases, everyday citizens can be equipped with sampling materials and identification keys to collect valuable ecological data to fill in gaps. Concerned citizen scientists can also help the public better understand the value of crayfish. These projects are also perfect outreach opportunities for volunteer organizations such as student chapters of the American Fisheries Society and Master Naturalist organizations. Someday, we hope to build a database of publicly accessible crayfish life history information to be used by conservation scientists.

There’s hope for the future. In his short essay, “Red Legs Kicking,” Aldo Leopold wrote, “This much at least is sure: my earliest impressions of wildlife and its pursuit retain a vivid sharpness of form, color, and atmosphere that half a century of professional wildlife experience has failed to obliterate or improve upon.”

Let’s not forget those little questions that we asked when we were playing in the creek as kids. In doing so, maybe we will be able to better appreciate, understand, and conserve the diversity of these important “river roaches” as habitats become more threatened and researches become further pushed to pursue “big questions”.Moore

Michael Moore is a graduate student at the Virginia Tech Dept. of Fish and Wildlife Conservation. His undergraduate research at the University of Missouri focused on crayfish life history. He writes an excellent blog, “Clinch Chronicles”, about his current research on using eDNA to better understand populations of rare Clinch Dace. 

Further reading about crayfish life history

Moore, M. J., R. J. DiStefano, and E. R. Larson. 2013. An assessment of life-history studies for USA and Canadian crayfishes: identifying biases and knowledge gaps to improve conservation and management. Freshwater Science 32(4):1276-1287.

Stearns, S. C. 1992. The evolution of life histories. Oxford University Press, Oxford, UK.

Taylor, C. A., et al. 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries 32(8):372–389.

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