Recently I took a weekend trip up to visit some friends at their cabin outside the city. It’s always great to get out of the concrete and glass of my daily surroundings and hit the lake. This particular weekend was during a recent heat wave and it was great to be in nature where the temperature was a little cooler. My friend’s cabin is in a bay with a lot of variation in the water level, causing a big difference in where the shore line will be at various points in the year. In order to combat this the docks have to be built reaching quite a way out into the water to ensure that the boats will not hit the bottom during low season. Their dock stretched out into the water about 100 feet (as seen in photo above) and made a great place to sit and spend an afternoon lounging and passing the time. While out on the dock I noticed that hundreds, maybe even thousands, of 2 inch minnows were huddled under the dock, possibly to use the shade as protection from the blasting mid-day sun. This made me wonder if these little fish made any noise as they whipped around each other in such tight quarters, so I grabbed my hydrophone and dropped it in the water to take a listen.
I quickly found out that the minnows wanted nothing to do with the shinny silver capsule of the hydrophone. The second it hit the water they all uniformly swam away a few feet and kept their distance from the intruder. Luckily I was doing nothing for the rest of the day but relaxing, so my plan was to simply wait them out. I figured if I left the hydrophone in the water for a long while the fish would start to accept it as part of the environment and eventually start swimming near it and then I could listen in. As time past I came to the conclusion that this was not going to work. After a long time they were still going no where near the underwater microphone. At this point my wife asked me what the hell I was up to, somewhat annoyed that I was doing work-esque experiments at a beautiful lake instead of just relaxing. Luckily she knows me well enough to realize that this is my form of relaxing. So when she heard my situation she immediately came up with the answer to my problems. I had to lure the fish in towards the mic, but I still did not know how, until she told me fish eat bread. What? Fish eat bread? I had no idea, and to be honest I was very skeptical of this even being true. Until I tried it and found out it is 100% true.
I poked a hole in the middle of a slice of bread, fed the cable for the hydrophone through the hole and then popped the little audio trap in the water. I had to put the cable through the bread hole in order to keep the bread slice from floating away on me. Next I tied off the cable on the dock so the length had the capsule of the hydrophone about an inch to two below the bread in the water. This time I did not have to wait long for the minnows to come over and investigate. With in a minute I had about 5 or 6 minnows taking little pecks at the bread and although it was cool to watch it even cooler to listen to. The little fish made great little wiggle sounds as they moved around the mic. Take a listen:
Then in another minute a whole other school of fish came over for a taste and then another wave of the little wigglers came after that. Soon there were hundred and hundreds of the tiny fish swimming all over the area near the bread slice, taking little bites. The sound of them all together became a lot more delicate and clicky. The sounds they were making were mostly the sounds of tiny little bites into the bread as they slowly nibbled away, sounding kind of like a wet static. There were also some sounds of their little tails whipping the capsule as they swam by. There were also other noises that I am not able to easily identify (listen to the video a few paragraphs below).
As time passed the fish were really putting a dent in the bread. First they ate their way through the crust and then worked on the interior until they managed to eat enough bread to free it from the cable of the hydrophone. Finally the slice was taken away with the current while the fish follwed it. The whole sequence lasted about 40 minutes.