When spending the day on the water, many people forget (or try not to think about) the vast ecosystem thriving below them. Plants, fish, mollusks, snails, snakes, and more live out their lives under the surface, whether or not they affect you. But have you ever considered how you affect them? While you may not be polluting the waters or physically disturbing any wildlife, new research shows that a day out on the water may still have detrimental effects on the natural behavior of fish.
Noise pollution is becoming an increasingly important field of study with more and more research showing the detrimental effects it can have on the natural behavior of animals. Extraneous noise has been shown to increase stress, cause hearing loss, and divert animals’ attention. Because sound travels further over water, many aquatic animals have evolved to rely heavily on these auditory cues, making it an especially important environment in which to study noise pollution.
Scientists at the University of Windsor recently published the results of a study testing the effects of boat noises on the behavior of fish both in and out of a laboratory setting. There is currently a debate happening among animal behaviorists about how to study noise pollution in aquatic environments. While working in a laboratory is certainly easier and more controlled, it is not as applicable to real world situations. To rectify this, experiments were conducted first inside the lab, and their validity tested in subsequent field experiments.
The team wanted to study the foraging behavior of the fish with and without the noise pollution, and came up with quite an ingenious set up. Nine holes were drilled into a sheet of plexiglass, and a chunk of worm was dangled from each one. In the lab, this sheet was placed on a platform above the tank, but in the field, they floated it on top of the water with pool noodles! An underwater speaker was placed near the worms that would play boat motor noises, or white noise. Trials were also done where no sounds were played, and also where the speaker was entirely disconnected. The team used black bullheads in their lab experiment because they have advanced hearing structures, and little of this research has been done on freshwater species. A Go-Pro camera filmed each trial, and the video was analyzed for two foraging behaviors: when a fish approached the worm with an open mouth, but didn’t get the worm, and when when a fish did get the worm. The amount of time a fish spent swimming erratically was also recorded.
The results? In the lab, fish showed a significant decrease in foraging events when the white noise was playing, and even more of a decrease when the motor noise was played. The fish also showed a slight increase in erratic swimming during the white noise, but a huge increase during the boat noise. Because the white noise and boat noise got such similar results, only the boat noise was used in the field experiment, as it has higher ecological relevance. The field experiments showed similar results to the lab ones; boat noise decreased the number of foraging events and also decreased the number of all species of fish visiting the worms, but fish with advanced hearing structures were the most affected. This replicability confirms that the results the group found in that lab are also applicable to wild fish as well.
But what does all of this mean? Well, while we may be focused mostly on the physical pollutants we put into our waterways, other aspects of our actions can have just as much of an effect. Our boats may be affecting a fish’s everyday habits, making them unable to get the food they need. It could even affect your fishing! What fish is going to go and forage for food right where there were just loud motor sounds? More research needs to be done in the future involving different species, different noises, and a longer period of time, but this is an important step towards understanding the impact we have on our environment.
Works Cited
Pieniazek, R. H., Mickle, M. F., & Higgs, D. M. (2020). Comparative analysis of noise effects on wild and captive freshwater fish behaviour. Animal Behaviour, 168, 129-135. doi:10.1016/j.anbehav.2020.08.004
