The Impact of Human-Generated Noise on Aquatic Animals: A Growing Concern.

There exists a linear relationship between the human-generated sound and health, behaviour as well as the well-being of animals just like humans. There is an increasing concern over the years on the impacts of the noise on aquatic animals, including fishes, and other reptiles. Even though the ever-increasing human activities are generating a lot of sound around the marine environment, very little information is known on the direct impacts of these sounds on reptiles, mainly the fishes (Amorim et al., 2018). Moreover, these sounds come from different sources, including noise from the ship, air guns, and pile driving. Therefore, there is a significant need to compare the impact on the stimulus of different sources independently.

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Besides, to learn about the environment as well as communicate, fishes have several sensory systems, including hearing. Moreover, fish make use of hearing senses to receive information even from greater distances around its environment (Amorim et al., 2018). Therefore, fishes can overcome the limitations of other sensory systems, including touch, vision, smell, and taste, to receive information through hearing in three dimensions. Furthermore, fish make use of sound in communicating with other fishes, detecting predictors and preys, migration, mating behaviour, and selecting habitats (Carder & Miller, 1972). Any activity that results in interference with the detection and response to relevant sounds directly affects its survival and fitness, not only for the individual fish but also for the entire fish population.

In this report, I will review the potential impacts of vibrations and the sound of approaching individuals on the swimming patterns of the goldfish. Besides, this paper provides further information on sound transmission and movements under the waters, particularly the concept of how particles move underwater. Moreover, in this article, you will gain an understanding of fish's acoustic behaviour, hearing, and sound production. However, different fish species respond differently to various sound sources under different conditions. Therefore further research is recommended. Besides, both immediate and long-term effects of sound exposure should be examined, especially on swimming patterns.

Over several years we have seen an increased interest and studies around the anthropogenic sounds and their significant effects on aquatic life. Furthermore, increasing human activities and movements around marine and freshwater environments have resulted in rising in these anthropogenic sounds. For instance, wave energy generation, shipping, seismic surveys, dredging and pipe and cable laying have significantly contributed to an increase in these anthropogenic sounds (Buscaino et al., 2010). The initial focus was on the effects of these sounds on aquatic animals. However, the numbers of marine mammals cannot be compared with other animals that contribute to more abundant aquatic biomass, including fishes. Therefore, concerns have grown over the years on effects these sounds poses to fishes, including how they influence the swimming patterns.

Several studies for the past years have highlighted the potential effects of sounds on the behavioural characteristics of a fish. However, some studies were conducted using a laboratory tank targeting specific species that are able to thrive in captivity as opposed to the other fish species that are different in terms of both psychologically and behavioural, for instance, the goldfish. Furthermore, in the regular and natural aquatic environment, the behaviour of fishes is entirely affected by the temperature, motivational state, body size, physiological state, and school size. Therefore, exploring and studying the commercially important fish should be done with a lot of caution. Besides, it is believed that better hearing capabilities among the fishes contribute to better behavioural responses as compared to those species that are less sensitive to sound (Buscaino et al., 2010). However, in most cases, this assumption is never correct, therefore calling for further investigation. For instance, swimming is not always affected by hearing capabilities.

Moreover, exposure to sound potentially damages the sensory cells and, after that resulting in hearing impairment or loss (Buscaino et al., 2010). However, the hearing loss is not permanent among the fishes. Besides, fishes can repair the sensory cells found in the inner ear after the damage of even temporary loss.

However, the impact of the sound is highly dependent on the degree of the behavioural response and, therefore, might be very low. Moreover, a more significant impact would be when the sound vibrations affect fish's movement, for instance, away from breeding or foraging, grounds, change of the migration patterns or interferes with reproductive activities (Amoser & Ladich, 2003). Besides, noise resulting from boating activities has been reported to cause some significant effects on fish's behaviour. I decided to choose goldfish considering its high sensitivity to sound, including the availability of data on its hearing and behavioural characteristics. Furthermore, I love goldfish, and I have been keeping them for more than one year. Goldfish is a well-known member of the Cyprinidae family of the Order Cypriniformes and possesses a Weberian ossicle (Amoser & Ladich, 2003). Weberian ossicles are modified cervical vertebrae adjoined to the ear. Besides, these Weberian bones are very critical to its hearing sensory system, contributing to enhanced hearing sensitivity. In comparison with the other fish species, goldfish have a broader frequency range of hearing as well as lower auditory thresholds.

Methods

I own an aquarium where I keep goldfish and decided to use them for the studies. The standard mess for goldfish was between 10.5 and 34.8 centimetres (Amoser & Ladich, 2003). Moreover, forty-two goldfish were used for the long-term noise exposure experiment. Besides, all the fishes were maintained in two groups of 600-litre aquaria made from glass, and corner filters applied accordingly (Bart et al., 2001). Furthermore, sixty-five percent of the water was changed at least three times per week with two aquaria water kept in different rooms where one acted as a control experiment and the other to house the noise-exposed goldfishes. Furthermore, the impact of the induced noise on the animals over a long period, between one to twenty-one days, was examined in groups of six and five fish.

The two experiments aimed to assess the effects, especially for short-term exposure to the sound vibrations from the induced noise (Carder & Miller, 1972). Besides, one experiment analyzed the response to the physiological stress in the course of the experiment duration. At the same time, the other focused on the behavioural effects of sound vibrations on temporary shifts on the hearing thresholds.

White noise was used to conduct bot experiments with a bandwidth between 0.1 and 10 kilohertz (kHz) at a total SPL (Sound Pressure Levels) of 160 decibels. A Sony MiniDisc player was used to induce the sound using an amplifier and an underwater speaker placed at the bottom centre of the aquarium. Besides, white noise was computer generated using a defined flat power spectrum occupying the entire bandwidth (Carder & Miller, 1972). However, the sound pressure levels were varied for long-term experiments with a maximum of 170 decibels. The SPL for the control experiment was operated within the ranges of 110 and 125 dBs at the farthest corners of the speaker (Carder & Miller, 1972). However, there was a very minimal sound vibration that could be heard outside of the noise tanks because the water-air interface resulted in a 40 dB loss in sound energy. Besides, none of the lost energy was known to pass into the rest of the tanks.

Glucose concentrations and plasma cortisol in the blood are the most common indicators of both secondary and primary stress levels in fishes. However, cortisol contributes to a highly rapid and transient response compared to glucose. Before our induced sound experiments, preliminary tests have been conducted as a positive control in evaluating both glucose and cortisol levels in response to physiological stress (Buscaino et al., 2010). Besides, a ten litres water tank was used to hold groups of goldfish for preliminary tests and the control group was left for 30 minutes while exposing the treatment group to repeated and continuous vibratory stress for thirty minutes.

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Results.

The results of the preliminary tests conducted using buckets as stressor indicated a significant increase in the post-stress plasma cortisol and glucose by 84-90 percent compared to the controls (Buscaino et al., 2010). Furthermore, the plasma concentration of both glucose and cortisol was noted to be directly proportional to the bleeding order, a clear suggestion of fish exhibiting stress response as a result of the netting of the removed fish. However, with the long-term noise experiment, noise exposure did not show any consequential effect on the cortisol or the glucose levels as opposed to the short-term experimentation where cortisol plasma levels were affected although glucose was not. Moreover, mean cortisol levels increased three times in every 10 minutes of noise exposure and reduced back to control levels after every sixty minutes as compared to the controls.

Discussion

According to the experiment, there was an initial startle response by the goldfish to the beginning of the white noise, which diminished within a short duration of time (Amoser & Ladich, 2003). Besides, the goldfish did not seem to avoid areas around the speakers placed under the water, nor did it try to move to neighbourhoods where speaker pressure levels (SPL) would be lower. Furthermore, there was initial erratic swimming at the beginning of the startle response, which was followed by a general increase in swimming activity. Besides, it is common for a loud sound to cause such behaviours in fishes (Buscaino et al., 2010). Moreover, fishes might show a transient behaviour characteristic in response to sounds, although the sound results to ear damages that occur quicker and has a long-lasting effect.

Furthermore, the sound has a direct effect on the swimming patterns of fishes. There is temporary and erratic swimming behaviour after exposure to noise, although the fish can return to normal after a short while. However, repeated exposure to these sounds could have a permanent effect on their behaviour, including potential habituation to the disturbances.

Fig: Relationship between sound power and the effect on swimming speeds.

References

Amoser, S., & Ladich, F. (2003). Diversity in noise-induced temporary hearing loss in otophysine fishes. The Journal of the Acoustical Society of America, 113(4), 2170-2179.

Bart, A. N., Clark, J., Young, J., & Zohar, Y. (2001). Underwater ambient noise measurements in aquaculture systems: a survey. Aquacultural Engineering, 25(2), 99-110.

Carder, H. M., & Miller, J. D. (1972). Temporary threshold shifts from prolonged exposure to noise. Journal of Speech and Hearing Research, 15(3), 603-623.

Amorim, M. C. P., Vasconcelos, R. O., Bolgan, M., Pedroso, S. S., & Fonseca, P. J. (2018). Acoustic communication in shallow marine waters: testing the adaptive acoustic hypothesis in sand gobies. Journal of Experimental Biology, 221(22).

Buscaino, G., Filiciotto, F., Buffa, G., Bellante, A., Di Stefano, V., Assenza, A., ... & Mazzola, S. (2010). Impact of an acoustic stimulus on the motility and blo...