Schooling, here we go again

[Tifftastic]

I have a deadline coming up, right before a LONG flight from Glasgow to Seattle to throw myself into the wolf den I call my family. So naturally, I am pulling a long night and avoiding most of what I am supposed to be doing in favor of reading slightly related articles in between meticulously rewording sentences and trying to squeeze in as much information as I can. In addition to that I'm thinking about shoaling and shoal numbers and was brought back to this video posted by the University of Glasgow Fish Biology Group (see bottom of post). Essentially, not all shoaling fish want to be part of a shoal. Some are more social than others and some want to be left alone and are not bothered about shoaling. There is also a gene for shoaling that has been identified and the strength of the desire to shoal can be impacted by environmental factors during development. For example in stickleback the male cares for the eggs and fry until they can survive on their own. There is a difference in quality of care between benthic (those that hang out on the bottom of a body of water) and limnetic (those that hang out in the open waters) males and interestingly those that tend to spend more time in open water, where predation risk is higher exhibit higher parental care and have offspring that are stronger shoalers. Now, this seems to make sense because its all to protect from predation, but if you take limnetic juveniles and let them be raised by benthic fathers, they don't shoal as well, indicating that it isn't purely genetic but also an effect of the early environment experienced.
Now all of this taken into account, how did we aquarium hobbyists decide that six was the magic number for school size? We don't know how social our fish are, they could be highly social and require interactions from hundreds to have their needs met, or they could be anti-social and want to be left alone. Why is six somehow the perfect number between the wild populations of hundreds to thousands and the sad, single, lonely neon tetra that someone decided was pretty, but didn't want to be bothered with buying more of?

https://www.facebook.com/video.php?v=131402743881253

source: https://www.facebook.com/GlasgowFishBiology

 

[wesleydnunder]

Hey Tiff! Glad to see you back...was afraid you'd left us.

I love the question; "Why the number Six?" I've often asked it myself...never did get a satisfactory answer, other than the link that OrionGirl posted on the Rant Thread. I anxiously await your conclusions...

Mark

 

[Tifftastic]

I've been lurking, been kind of busy with starting this PhD and haven't had as much time to look at shoaling as I've been trying to learn about parental care and epigenetics O.O

I wanted to see if I could find any explanations of the minimum number of six through a quick google search and I found a variety of recommendations, which I find interesting.

This article from 2012 (I believe) talks about how 10 is actually a better number than six. But they went no higher than 10, so I'm sure the natural behaviors would be exhibited better by larger numbers.
http://www.nbcnews.com/id/31952465/ns/technology_and_science-science/#.Tkez32H_yx4

Then you have this random person who says that fish usually start in shoals of 10-20 and join another shoal. Which I find to be an odd thought since fish shoals usually begin with siblings and then increase in size and many broods are MUCH larger than 10-20 fish, so this is still a generalization.
https://uk.answers.yahoo.com/question/index?qid=20140117204820AAE4hMA

Other sites just say "the minimum number is six" with no explanation. When I first had it explained to me I was told 3 is the bare minimum. Because fish that shoal never have a true pecking order and the leader is often fluid (this has actually been studied and is true, I have many references on it if desired). So the fish are constantly picking at each other and if you have only two, they will stress each other. But if you have three one will get a break from time to time and you will have happier fish. This makes sense, but also for fish that live in the thousands seems very small a number. So is it just six because that's better than three? Then what about the "odd number" thing that people swear is true for some species, particularly piranhas. So, we still have the why six? That study from 2012 presented at the SEB (an awesome conference that I may get to go to this year!) suggests that fish are still stressed at numbers under 10.

 

[smitty]

A great topic to think about. I am going to look into it during some free time. But really I never thought schooling had a set number starting at 6, but did realize it was a common number.

 

[SnakeIce]

Six is an easy number to pick on to slow down the new fish keeper at the store that in their enthusiasm starts with the idea of getting one of every little fish they see. Gotta collect them all. Wait, you mean they need friends?

I have a hunch tank size plays a part. I know red minor/serpae tetras have a loose social structure, and if you cram that in to small a space they get nasty to each other and to other fish. If you give them enough room between individuals they mellow out. So I think the number of fish you can keep depends on both personal space needs and social needs. Limit either one to much and you have a stressed, abnormal acting fish. It is easier to err on the side of not limiting personal space for a fish than it is to be sure you have enough for sufficient social needs.

 

[Astarell]

I don't know where six comes from but I do use 3 as my magic number. I figure that way if one of them is aggressive, it won't get frustrated by being alone with no one to lord it over, and it also won't henpeck just one companion into misery. If there are three, the henpecking gets spread around enough that no one fish is totally miserable, and if they're more the loner type they can still go be off on their own because it won't be too crowded. More is fine, obviously, but I feel 3 is minimum. Just my 2 cents.

 

[fishorama]

I always suggest 6 for a minimum for a better gender mix, less aggression & possible breeding activity, always interesting.

What is wrong with this thread, it keeps jumping up & down making typing almost impossible? Is it the links?

 

[Tifftastic]

What is wrong with this thread, it keeps jumping up & down making typing almost impossible? Is it the links?

I think for some reason there is an issue with the embedded video, which weirdly worked just fine in the preview and also when I first posted. . . It takes a little while for the video to load I guess, and then the jumping stops.

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The problem with six for me is that it is still so small. I don't always see how it is much better than three, personally. That being said, I have done my shoal cohesion experiments with four and ran out of time to do it with six, but this year will be upping the numbers and looking at how shoal cohesion changes as numbers increase.

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Yesterday (and today), we had (have) a guest speaker David Reznick from UC Riverside. He does a lot of work with guppies in Trinidad. He briefly mentioned at the end of his talk yesterday that guppies from high predation environments have the tendency to shoal, and to shoal tighter more so than those from low predation environments. So, taking that into account and the instances of solitary guppies that he mentioned when my lab met with him today, I would have a hard time continuing to suggest to people that guppies MUST always be in an aggregation/shoal/school and particularly that they be in numbers of six.

As more and more work comes out on shoaling behaviors in different species, I believe we will find that not only is our suggestion of six far too little (something most people know), but our insistence that captive raised fish who shoal in the wild will still require a large shoal in captivity. Not only that, but I personally predict that some fish actually suffer when put into a large (relatively for captive states) shoal, based on their individual personalities.

 

[myswtsins]

I think 6 is used because it is a reasonable number. It is enough to get a good mix of M/F, to create the idea of a shoal and small enough number to be comfortable in most aquarium sizes. But personally I always try to go for large groups of only a few species. I always end up with some leftover oddballs though too. I also think that too large of a shoal in an aquarium does defeat the purpose. Very interested in your findings Tiff, I'll be following along.

Yes, the video in the first post is why the page jumps and I was able to see it just fine when it was first posted also. I just "stop" the page from loading and it stops the jumping.