Project Results

My research is now published! Once the full version is available, it should be free to view, but if you would like a copy of the early version, place let me know at NoahBressman@gmail.com

Overall, I found that walking catfish use vision and chemoreception to orient on land. They can use the taste buds on their whiskers to find nearby prey through taste. They can also detect attractive compounds from distant bodies of water and move away from noxious compounds while on land using some kind of chemoreception (taste, smell, and/or nociception), but more research is needed to determine the exact mechanism. They also seem to use storm drains to disperse underground, emerging from storm drains during floods. They take advantage of moist ground to disperse overland, eating some wet bugs and worms along the way.

About This Project

I study amphibious fishes, how they move around on land, and where they go while on land. In this study I will travel to southern Florida to run experiments on invasive walking catfish. I hypothesize that this catfish uses visual and chemical cues to navigate on land and migrate to new bodies of water. To test this hypothesis, I will place catfish on land for experiments and expose them to a variety of sensory cues to observe their responses to stimuli.

Ask the Scientists

What is the context of this research?

One summer, I noticed a live fish in a hallway and asked, "how did it get there?" After a couple of years of research, I figured it out! This fish left a tank in the lab because another fish was trying to eat it, and then went to a spot on the floor where sunlight was shining through a window. The fish used vision to find its way to that spot, and thought the reflection on the tile floor was water. After publishing this research in the Journal of Experimental Zoology, I wanted to figure out how other fishes find their way around on land. Do all fish use the same senses and cues? Or do they navigate land in different ways, depending on their motivation? Currently, not much is known about the behaviors and sensory biology of fish on land.

What is the significance of this project?

Several invasive fish species around the world, like walking catfishes, snakeheads, and climbing perches, are able to move around and survive on land for long periods of time. This gives these fish the potential to quickly increase their invasive range by spreading overland between bodies of water. This project would seek to figure out which senses and sensory cues invasive amphibious fishes use to find their way around on land, and potentially find new bodies of water. In these new bodies of water, these fish can disrupt the ecosystem, endanger native species, and impact fishing and other human activities. By understanding how these fish can spread overland, we could learn how to prevent them from spreading more, or at least help manage the spread of these harmful species.

What are the goals of the project?

The goals of this project are to determine which senses and sensory cues the invasive walking catfish (Clarias batrachus) use to orient and navigate on land and assess their ability to spread to new bodies of water by moving overland. These fish are frequently found on land in southern Florida, particularly while it's raining and/or at night. While placed on land for experiments, the catfish (n = 60) will be exposed to a variety of sensory cues (e.g., reflective surfaces that resemble water, odors associated with water, 3D printed prey, etc.) and observed for responses to stimuli to determine if/how they find water and prey while on land. This project will start January 2019 (when my collaborators will have fish for me), and will include wild observations for natural comparisons.