Anthropogenic Interference in Goby Mating, by Ben Olenick

A freighter ship floats away from the harbor blaring its horn for other watercraft to note its presence and intentions as it sails out onto the open sea. The use of horns and other audible cues is common among the shipping world as it provided a form of communication amongst ships before the invention of the radio. Accordingly, it is known that many other animals other than humans use vocal and auditory cues to communicate, including fish. However, as with many human activities, human-induced noise pollution is impacting fish in all forms of bodies of waters. Fish use sound transmitted through water to communicate with fish for multiple purposes: schooling, hunting, mate searching and breeding. Gobies (Gobiidae) are known for their vocal mating behavior. In this interaction, males will produce drumming sounds with varying intervals to market their sexual quality to females as opposed to using a primarily visual display of quality (Amorim et al. 2013). Anthropogenic noise pollution poses a threat to the success of mating in the goby example provided. This is due to the fact that not only does the noise from ships and drilling drown out the drumming mating calls of gobies but also due to anthropogenic noises creating constructive or destructive interference in the wave frequencies of the mating drums of the gobies. Therefore, if the soundwaves of anthropogenic sources match the frequencies of the male goby’s mating call, then population numbers will dwindle because they will be less likely to identify a true mate with excess background noise.

Levels and frequencies of anthropogenic and naturally occurring sound sources in the marine environment. Specturum Noise Level ("Acoustic intensity per Hertz") versus Frequency (measured in Hertz or "cycles per second").  Source.

Naturally, the threat of anthropogenic noise pollution threatens some species more than others. For example, according to Amorim et al. (2013), the Painted Goby (Pomatoschistus pictus) is a vibrantly colored species of goby that was believed to utilize coloring to attract female mates in a display of health, however, was discovered to utilize vocalizations as the primary attractant force between males and females. While there is a correlation between body size of males and the depth and frequencies of their drumming calls, females would not notice the males before they processed the healthiness displayed in their vocalizations. This fact has the potential to ruin the population size, and thus, the genetic richness, of the Painted Goby. Anthropogenic noise pollution from fracking or motors on boats have the potential to match the frequencies of the drumming songs of the Painted Gobies which would make the males searching for mates go unnoticed and or attract the females into dangerous situations near the sources of the sound. In doing so, the reproductive success rates of the species will go down for both sexes of goby. With audible cues being their main source of mating displays, a mutation for female shift in mating display preferences would be necessary to keep the species population stable if anthropogenic noise pollution was to remain at its current levels.

Painted Goby Pomatoschistus pictus  CC BY-NC-ND 2.0. Photo by

Asbjørn Hansen 

Certain individuals have set out to see if anthropogenic noise pollution has a quantifiable effect on the mating success of gobies. Blom (2017) found that males had a 14% mating success when exposed to continuous anthropogenic noise in a laboratory situation. In addition to this, even intermittent noise pollution produced a lower mating success rate in males at 39% mating success; this falls 15% short of the success of the control group, however, there is a noticeable decrease in both testing groups and a significant difference in those expected to the long term effects of continuous noise pollution. This experiment was conducted by placing fish in a tank that had a resonating tube with speaker attached to it to transmit the noise played over the speaker. Those in the control group were not subjected to any human-induced noises. While there are some flaws in this experiment, such as the difficulty to truly reproduce the noises generated by ships and large machinery in a laboratory setting, this experiment confirms that the mating rituals of gobies are interrupted in significant ways with the presence of unnatural sounds. Although there are physiological and behavioral effects caused by the presence of the stressors, the damage done to the mating success in these species puts this family of gobies at risk (Blom 2017).

While there are clear direct effects on the goby mating systems, there is still much that is not understood as to all the ways anthropogenic noise pollution disturbs this process. However, we can look to other studies on the effect of noise pollution in aquatic systems to better understand how noise pollution negatively impacts the ecosystem. In a recent study conducted on the Pacific Oyster, it was discovered that noise pollution stunts the growth and fat metabolism by disrupting metal bioaccumulation and filtering patterns of the oysters (Charifi et al. 2018). Noise from cargo ships lowered overall oyster activity, leading to disruptions in circadian opening and closing of ventilation and filtration of the water by oysters. This has serious ecological implications for the entire ecosystem as oysters provide many ecological services for the environment. Seeing as oysters are often a part of the diets of many gobies and provide filtration of the waters that the gobies inhabit, this leads to a negative indirect impact on the vitality success of gobies in systems affected by anthropogenic systems. With less nutritional sources and unfiltered chemicals in the water, gobies may not make it to the mating stage in their life cycle. Even if they do reach this stage, there is potential for the gobies to be malnourished and not be able to produce strong, fit, viable offspring. Further research should look into the effects of noise pollution on the metabolism and homeostatic processes of gobies since there is evidence it has negative effects on the health of other animals.

In summation, the preferred mating selection in many gobies of using vocal cues is at risk in a world dominated by human-induced noise pollution. This is in response to how the soundwaves of anthropogenic sources match the frequencies of the male goby’s mating call, resulting in diminishing population numbers because gobies will be less likely to identify a true mate with interfering anthropogenic background noise. However, there is potential hope for this style of mating in the gobies. As climate change and shortages of fossil fuels are causing humans to search for more eco-friendly sources of energy and processes, the waters may become safer for the gobies that inhabit them. As solar and nuclear power expand into many forms and electric engines are the next step towards reducing the carbon footprint, consequently, the engines become quieter and the need to drill for oil is slowly disappearing. Through this, the populations of gobies will be able to bounce back to their natural strength. Nevertheless, something must be done to protect this mating mechanism in the meantime, otherwise, there is no telling what the future may look like for the gobies in our waters.

References

Amorim, M. C., S.S. Pedroso, M. Bolgan, J. M. Jordão, M. Caiano, and P.J. Fonseca. 2013. Painted gobies sing their quality out loud: acoustic rather than visual signals advertise male quality and contribute to mating success. Functional Ecology 27(2):289-298.

Charifi, M., A. Miserazzi, M. Sow, M, Perrigault, P. Gonzalez, P. Ciret, S. Benomar, J-C. Massabuau. 2018. Noise pollution limits metal bioaccumulation and growth rate in a filter feeder, the Pacific oyster Magallana gigas. PLOS ONE 13(4): e0194174. https://doi.org/ 10.1371/journal.pone.0194174

Blom, E. L. 2017. Sexual signalling and noise pollution - implications for courtship behaviour and reproductive success in two vocal species of marine gobies. Doctoral thesis. University of Gothenburg, Sweden.