The two fish in this YouTube clip are having a serious disagreement as some amused humans watch on. The footage was captured in a fish tank, and it is likely between a jawfish and a goby. They are literally spitting sand in each other’s faces! But why would they do this, and is this usual behavior? Read on to discover the potential explanations.
Are the Fish Feeding?
It is not unusual to see fish spitting out sand and small pebbles. It can be part of the feeding behavior. They do not have teeth, and therefore cannot chew food before swallowing. They ingest small stones, which are stored in their muscular gizzard and help grind up food for digestion. Fish that do this include carp, tilapia, cod, trout, and perch. They prefer to hover a few inches above their den so they can have a 360-degree view of their surroundings. It is also common to see fish such as goldfish and koi pick up small pebbles or sand and then spit them out after filtering out any edible bits. However, the fish in this clip appear to be expelling the sand and dirt in a more targeted way, indicating that this is not feeding behavior.
Are They Building Dens?
Goby fish are excellent den builders.
©Osama Abuassonon/Shutterstock.com
Some fish species, including jawfish, build dens and tunnels in sand by digging, taking sand in their mouths, and spitting it out. The goby fish group is sometimes called ‘engineers’ because they are such prolific den builders. The tunnels can be quite long, with branches and junctions. They are used as somewhere to live and for protection. It is likely that the goby in this clip has constructed a tunnel like this or is in the process of doing so. However, it appears that a jawfish has built a tunnel nearby, which is where the conflict begins. There is more happening here than just den building.
Captive jawfish, such as the dusky jawfish, are enthusiastic tunnel builders. Some inexperienced owners are shocked by the way they constantly move sand around as they build new burrows. They prefer to hover a few inches above their den so they can have a 360-degree view of their surroundings. However, sometimes they will stay in their den and simply stick their head out to see what is going on. They are usually peaceful fish, but they can be territorial.
Are the Fish Having a Confrontation?
The most likely explanation is that these two fish are both displaying territorial and defensive behavior. Neither of them is happy about the proximity of the other den, and so they are making this clear with a sand spitting display. It’s a bit like humans hollering ‘back off’ to each other! They like to establish a perimeter around the entrance to their tunnel and don’t like it when other fish encroach on it. Gobies may not always realize that their actions are bothering the jawfish. One owner reports seeing a jawfish deliberately grab a goby in its mouth and physically remove it from its territory, but it is unclear if this is typical behavior.
