Hello dear reader,
We are The Guppy Girls and during a week we compared how guppies react to sound from how a frequency analyzer reacts to sound.
Every good fisherman knows that he needs to stay silent while fishing at the water’s edge, but have you ever asked yourselves why? (Here is a video where you can see the impact of noise). This is the question that started we have been trying to answer this past week. Therefore, we tried to compare the reaction (change of speed, attitude for example) of the fish with an electronic captor - a phone - exposed to different sound frequency.
Before continuing, you need to know that the sound is a wave, characterised by its frequency and its amplitude. The wave propagates itself in all directions of the air but it is also the case in water. The transit of this wave provoke a vibration in the middle that it is passing through and it becomes possible to quantify the incoming sound thanks to a vibration captor.
Now let's focus on fish. Fish can hear a sound if its frequency is between 150 Hz (Click here if you want to look at the impact of sound) and 1000 Hz (or here), and some of them can even hear up to 3000 Hz (or here ) thanks to their swim bladder. The swim bladder is a kind of air bubble, and when it is located next to the intern ear, it acts like a sounding board and allows amplification of the perceived sound. ( Here is an article that tells a lot on the hearing of fish)
We first created a protocol to study the fish’s reactions and bought fifteen female guppies, a small plant and placed them all in an aquarium. Then, we placed five fish in five jam jars in five different location of a room, at constant light, and quite isolated from external noise. After a fifteen minute break (to let the fish adapt to their new environment), we started to film from two different angles (side and above). We filmed 30 seconds without any sound and then we added the frequencies for 30 seconds and at last filmed 20 seconds after the end of the frequency. This was the kind of video that we obtained. We tested three different conditions : 200 Hz, 600 Hz, and 1000 Hz and did two controls: 0 Hz and 3000 Hz. The controls are there to see the difference of reaction between a sound they can hear and something they are not supposed to hear. We did the experiment twice on 10 different fishes. No fish stayed more than 45 minutes in a jar and no fish were harmed.
We then analysed the videos thanks to the software Tracker by tracking the fish on every ten image in order to get its position in x, y and z and deducted from that their speed. According to our results, the fishes seems to move a bit faster when their hear sounds, but their is no obvious reaction.
Average speed in function of time during the sound :
We can see that at 200 Hz the speed is higher than at 0 Hz. This shows us that sound may have an impact on the reactions of fish
For the electronic captor, we thought about using a vibration captor. Sadly, after numerous tentatives we did not managed to make it work properly. We therefore used a smartphone application that analysed incoming frequencies. We dived the phone in jars full of water that were located at the same spots as the fish. We did two replicates for each of the five positions and conditions. From this experiment, we saw that the analyser was very precise and accurate as you can see for the 3000 Hz in the graph below.
Results at 3000 Hz :
The measured frequencies are very closed from the theoric frequency. This shows us the accuracy and the precision of the device
To concluded, if we had more time, we would have been able to analysed more videos from the other frequencies we filmed, and maybe we will have been able to see more reactions from the fish and determined if he can really hear.
No comments:
Post a Comment