Vancmann wrote:Why Loaches Shadow.
Including my loaches, it is consistent across the board that they shadow one another. Also, I have seen my bigger loach turn around to give a strong snap to the smaller one following that makes me think she is saying, " I have had enough!! Go bother someone else". Sometimes a group of similar sized Clowns shadow each other, like a dance, in a “clump” when they are happy or when they are playing by the waterfall in my river tank. This behavior seems to be programmed in loaches to have that natural instinct to shadow another loach from a small size. Regarding why shadowing happens, I have a Hypothesis based on observing my loaches for many hours at different times and in water movement.
First, some facts:
1. Loaches are highly social, can't exist alone for long (at least happily).
2. They know and remember each other.
3 They sometimes form little sub-groups within large groups.
4. They expend lots of energy to establish leader/pecking order.
5. Their natural habitat exist strong currents, floods and fast flowing waters.
Here are a few assumptions:
In rivers where there can be floods, loaches will have to swim to resist being washed down stream unlike their hillstream cousins who can attach themselves to rocks. They may have to swim vigorously for long periods just to stay in the same place as a group, a tight one, and they will have to have fun doing so.
Based on these facts, I think that loaches do this for two reasons:
1. To stay together as a group. The fact that loaches have a pecking order means they have to establish a group and they have order in the group (pecking order). In the turbulent conditions of their environment, they will have to do what they can to stay in the group and that may be sticking closely to a stronger leader during rough times.
2. To expend less energy fighting the resistance of current.
Birds on long flights do this; they fly in a “V” formation to reduce friction as a group. The leading bird gets rotated out. Since loaches have a bond within their group, they will have to stick together during the monsoon floods or heavy rains. To me it seems that a school of loaches with their mouths bunched up or in a line will have less resistance and a greater chance of sticking together. They can also stick themselves in a log, I guess.
All this said, why my Botia almorhae (Yoyo) tries to shadow my Clowns and Modestas or in the past, Angelfish, African Cichlid, Rainbows, Sharks…. is probably not mating behavior or any of the reasons I discussed. Until we have someone to track, record and document these fish in their natural habitat for a 2-year period, this will only be a hypothesis and they will truly remain a mystery.
Vance, I applaud you in coming up with this list of ideas.
However, from my experience and observations, I can't say I agree with all of them (sorry!).
I do concur with facts 1-5 that you listed, but not with the two reasons which may be behind why they do this.
I have seen shadowing pretty much every evening in my clown aquarium for years and years now. When I observe them, they do not always parallel swim when in the path of fast currents, indeed sometimes it starts in a quieter area of the tank when beforehand the loaches had been at rest. They
do parallel swim in the currents, but I just wanted to point out that in my tank it's not always the case. Also, when they are in the full force of currents, I have frequently seen them shadowing a larger specimen (sometimes several on each side of the main fish) and they go round and round and round whilst the big one appears to try and shake them off. In no way is the larger one offering any shelter from the currents or encouraging/helping them to stick together.
My clowns also seem to shadow other clowns at random, depending on who is around and nearest to them when they decide to start it off. They never choose just one leader and stick to shadowing her/him and they may go from one to another within the same excited shadowing spell.
The fact that I have seen them carry this out in all areas of the tank, in areas of high and lower flow leads me to think that it is not for aerodynamic reasons. Their bodies are pretty streamlined as it is and I imagine (although I obviously don't know this for sure) that in the wild they remain quite hidden amongst aquatic debris and stay close to the bottom for much of their time, so I find it difficult to visualise them swimming/shadowing to aid their movement into forceful currents (although some species such as
Y. modesta are migratory and probably do have to spend time moving against the currents). And although they are a shoaling species, I think they are already more than capable of moving against powerful currents themselves (in a group but not necessarily touching), even smaller specimens.
Anyway, I'm sorry to disagree!
I still reckon it could be more of a social bonding behaviour. My fish are certainly very excitable when it happens and others often join in themselves once they see it going on. The larger fish do not always appreciate it and seem to get quite exasperated when it continually occurs.
Emma
. I am not saying I am correct so it is ok to disagree and I don’t take it personally. Like you, I also have seen my fish shadowing/parallel swimming. They do it with what seems like any random loaches since I have had them many years ago and for no/any particular reason. Even long before my high flow river tank that was constructed 3-4 months ago, they shadowed. I did not mean to use the flow of my tank as the basis of my hypothesis. Although part of my tank turns over 72 times per hour, they manage to glide through this very effortlessly. Our tanks are in no way, not even close, to the conditions of a real river or a flood condition in terms of current and distance to swim to prove they shadow for this reason. Furthermore, I don’t think that most of us, if any, could duplicate those conditions so I can’t really use the flow of my tank and the environment of a tank to prove they shadow or behave in any similar way for the same reason in the wild. An example, lion cubs and juveniles in captive and in the wild have the habit of running behind their siblings to trip them with their front paw in play. It is social, it is instinct, and it is practice. In the wild, this skill comes in handy for a totally different reason, to catch their prey for their survival.