We just published a new paper ‘No negative effects of boat sound playbacks on olfactory-mediated food finding behaviour of shore crabs in a T-maze‘ and it’s open access (HTML/PDF)! The paper is authored by Jostijn J. van Bemmelen, Hans Slabbekoorn and myself.
We are interested in the effects of man-made noise on marine life. Naturally, one would expect disturbance of behaviour that relies on biologically relevant sound. However, the processing of noise by an animal, may also interfere with the processing and interpretation of non-acoustic cues; for example, an olfactory cue (smell).
To study this, we allowed shore crabs to find food in a T-maze. We placed a food item in one of the ends of a T-maze. The crab could not see or hear the food, so had to find it based on smell. To facilitate this, we created a continuous waterflow from both ends to the starting area of the maze (as demonstrated in the color-test below). We tested two crabs at the same time and exposed about half of all of them to boat sound playbacks and the other half to ambient (background) sound playback. We scored how fast and efficient the crabs were in finding the food. Crabs that were exposed to boat sound were not slower or less efficient in finding the food, so we concluded that boat sound did not interfere with the processing and interpretation of smell in the current experiment.
In the YouTube-playlist above, you find several example trials (at normal speed) and some additional explanation on how we conducted the trials.
We just published a new paper ‘Effects of seismic airgun playbacks on swimming patterns and behavioural states of Atlantic cod in a net pen‘ and it’s open access (HTML/PDF)! The paper is part of the PCAD4Cod project and is authored by James A. Campbell, Hans Slabbekoorn and myself.
Increasing amounts of studies are being conducted on the effects of sound on marine life, including fish. However, it remains complex to translate results from controlled experiments to consequences for fitness of an individual or population. A first step might be to quantify time spent performing particular behaviour, and changes therein due to sound exposures. In the future, these changes in time budgets may be translated to changes in energy budgets, and consequently to changes in growth, reproduction, and mortality.
We used Atlantic cod as our study species and tracked them for about a day while swimming in our floating pen set-up (see pictures). After about 20 hours of baseline conditions, we exposed them to an hour of seismic survey sound playback. Firstly, we showed that the cod did not immediately changed their swimming patterns upon sound exposure onset. Next, we used statistical models to classify the behaviour of the fish and modelled the behaviour as if no exposure had taken place. Here, we saw that some fish seemed to have changed their time spent performing certain behaviour. This may be translated to changes in energy budgets and consequently individual and population fitness consequences in the future.
We just published a new conference paper ‘Exploring effects of sound on the time budget of fishes: An experimental approach with captive cod‘ and it’s open access (PDF)! The paper is part of the PCAD4Cod project and is authored by Daniël A. Wille, Hans Slabbekoorn and myself.
There’s an increasing interest into the effects of anthropogenic sound on marine animals including fish. A variety of studies is being conducted to gain insight into these effects. Ultimately, we want to gain insight into the effects of sound on individuals’ fitness and population levels. Modeling studies show that changes in energy expenditure and intake have most potential to lead to population levels effect. So, it’s important to study the effect of sound on individuals’ time and/or energy budget.
Ideally, this is studied in the field, but it’s very challenging to track free-ranging fish in their natural environment at high resolution. For that reason, we conducted a pilot study in a basin. We videoed 3 pairs of Atlantic cod for 7 hours per day, for 6 consecutive days. We exposed them to the playback of seismic survey sound for 3 consecutive days and a silent control for another 3 consecutive days. Each morning, we introduced live crabs in the experimental basin and the cod exhibited natural foraging behaviour by scanning and lifting patches of oysters in search for the crabs.
From the daily 7 hours of video footage, we extracted 20 second clips every five minutes (see example clips below). We scored the most dominant behaviour of both fish (foraging, swimming or stationary). In this way, we got insight in the activity budgets of individual cod with and without sound exposure. This can be translated to energy budgets by determining the energy expenditure and intake in all behavioural states.
We just published a new paper ‘The role of ambient sound levels, signal-to-noise ratio, and stimulus pulse rate on behavioural disturbance of seabass in a net pen‘ and it’s open access (HTML/PDF)! The paper is a collaboration between Leiden University and Wageningen Marine Research and is authored by Errol (Y. Y.) Neo, Erwin (H. V.) Winter, Hans Slabbekoorn and myself.
We are interested in the effects of man-made sound on marine life, including fish. Sound exposures can have a range of effects on fish; it may mask communication or other biological relevant sounds, elicit physiological and behavioural responses, and may even induce physical damage (close to a loud sound source). The sound levels are often used to predict the potential harm of sound exposure, however the acoustic characteristics of the environment (ambient noise) and sound exposure itself (the potentially disturbing stimulus) may also influence the behavioural responsiveness of animals.
Underwater, ambient noise mainly originates from water surface roughness from weather conditions and boat noise. When ambient noise levels are higher, a potentially disturbing stimulus may stand out less strongly (lower signal-to-noise ratio) and thereby elicit a milder behavioural response. Also, the potentially disturbing anthropogenic sounds themselves vary in acoustic characteristics which may affect fish differently, for example the rate at which poles (e.g. of wind turbines) are being driven in the seabed or the rate at which airguns of seismic surveys are being fired.
We tested the effect of such acoustic characteristics by exposing 16 groups of four European seabass to multiple impulsive sound treatments that varied in elevated background level, pulse rate, and pulse level. We implanted the fish with acoustic tags to be able to track the positions of the individual fish. We showed that the seabass increased their swimming depth after the start of the sound exposure, however the variation in the response could not be explained by any of the tested acoustic characteristics. Nevertheless, based on our review of the literature, we think it is worthwhile to continue on this line of research by testing wider ranges of signal and background levels.
Citation: Hubert, J., Neo, Y. Y., Winter, H. V., & Slabbekoorn, H. (2020). The role of ambient sound levels, signal-to-noise ratio, and stimulus pulse rate on behavioural disturbance of seabass in a net pen. Behavioural Processes, 170, 103992. DOI. [Open Access: HTML/PDF]
P.s. During the field season in which we collected data for the current paper, the Dutch TV programme ‘Vroege Vogels’ visited our field site to make an item on the effects of sound on fish in general, and about another study we did on an acoustic deterrent device for fish. For this, we also used the floating pen and a highly simular experimental design, so it may be interesting to watch the tv item (from 14:35 min on): https://www.bnnvara.nl/vroegevogels/videos/283480