Shoals and schools, what are we keeping?

HoldenOn

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Hey all,
I was doing some deep dives in the "scientific section" of this forum and found most, if not all, of the posts really interesting. That being said, it seems we lost some of our science friends over the years, and this section has slowly become less and less used. I thought this concept was interesting, so I thought it could make a cool thread.

A thread started in 2014 talked about the intelligence of fish, and in 2018 user Colin_T said this,

"Some years ago we got a group of wild caught Melanotaenia boesemani (rainbowfish from West Papua New Guinea). The boesemani were only about 2 inches long and still young so we put them in a 6 foot tank with a group of about 50 adult cardinal tetras. The tetras were pretty good size and we didn't think there would be any problems because they were nearly the same size as the boesemani.

All went well for the first day or so then one day we noticed the cardinals hiding in one corner of the tank. We tested the water and it was fine so we watched and waited and nothing. We moved out of the room and watched from around a corner and the boesemani were hunting them.

The boesemani split up into 2 groups. One group went along the front of the glass towards the cardinals, while the other group created a wall with their bodies and basically pushed the cardinals into the corner. The group that went along the glass raced in and attacked the cardinals while the group that created the wall held position to prevent any cardinals escaping. After a few minutes the groups swapped position and repeated the scenario. After that we removed the boesemani and put them in a separate tank.

I have seen the same hunting/ feeding behaviour in Geraldton WA, when a group of tailor trapped a heap of bait fish in a man made bay that was about 20meters wide and had limestone walls on 3 sides. The tailor split into 2 groups and one group made a wall preventing the smaller fish from getting back out to see, while the second group went in and fed. Again after several minutes of feeding the groups swapped and feeding continued.

Interestingly none of the tailor were interested in fishing lures that we were cast in during the feeding frenzy. They were only going after the bait fish. We had a number of different lures being cast in and the fish did swim past the lures but completely rejected them. This feeding pattern happened pretty regularly in this same bay.

The boesemani are lake dwelling fish that occur in freshwater and have had no contact with oceanic species for thousands of years, and therefore thousands of generations. Yet they showed the same hunting behaviour as wild oceanic fish. Is this a learned behaviour or inherited?

Domesticated boesemani (fish that have been bred in captivity for 10 generations or more) never showed any behaviour like this. However, when the domestic boesemani were housed with the wild ones, they quickly joined in feeding frenzies and made walls to heard smaller fish into corners. We used Gambusia not cardinal tetras during these experiments. Once the domestic and wild boesemani were separated the domestic fish never behaved like that again, even tho the wild ones continued to do it."
Quote was shortened for ease of reading. Credit goes to @Colin_T

When I was first interested in keeping fish I asked user Byron if there were any small "schooling" fish that I could keep. He replied by saying,

"Technically no freshwater fish species, or very few, "school" in the sense of remaining in a pack and hunting together. Shoaling as I tend to use it refers to fish that must be in a group of their own species, no matter how they interact; they may swim together at times, or they may remain apart much of the time. The important factor is that there are several of them in the tank to provide for their sense of security by living in groups of dozens if not hundreds naturally."
Quote was shortened for ease of reading. Credit goes to @Byron

Now, if we were to go by Byrons definitions of schooling and shoaling, which basically boil down too: if a fish is swimming with other fish similar in size, shape and color for social purposes and/or security reasons, it's shoaling. If it is swimming with other fish similar in size, shape and color in a coordinated manner in order to survive or obtain food, it is schooling. At this point if we are to refer back to Colin_Ts post, we can begin to see some similarities. In his post he says that his wild rainbow fish cooperated in a coordinated manner in order to obtain food, which by definition would be considered schooling. He also says that his domesticated rainbow fish recognized the behavior and joined in. This raises the question of wether semi-aggressive domesticated fish that are kept in groups, such as large tetra, rainbow fish, gregarious cichlids, etc. are actually shoaling, or schooling. If we say they are schooling, where does the line get drawn, when does a fish stop schooling and start shoaling, and how, if one even can, could someone determine this?
 
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Colin_T

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school vs shoal. I always took school of fish as being a single species of fish living in a group, whereas shoal of fish was a group of fishes containing multiple species that were living together. Or vice versa, can't remember these days but it was in an ichthyology book.
 
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HoldenOn

HoldenOn

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school vs shoal. I always took school of fish as being a single species of fish living in a group, whereas shoal of fish was a group of fishes containing multiple species that were living together. Or vice versa, can't remember these days but it was in an ichthyology book.
Interesting. So you are saying we are keeping schools when we have a group of say 10 tetra, but a shoal when we have some green corydoras and bronze corydoras mixing.
 

AtomicFish

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a school is when a single species of fish swims together and a shoal is a whole community of fish swimming together. at least that's what I think. in the movie finding nemo a school was multiple fish together.
 

seangee

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My description of schooling is where the whole school moves as a single entity as if they have a telepathic connection. I have seen this several time in the ocean where thousands of fish move in harmony and (seemingly) randomly change direction, but every fish stays in formation. Truly spectacular to watch. Most tropical fish don't do this, or we don't have enough of them in a big enough space. When our fish shoal tightly it is usually because they are stressed or threatened. They huddle together for security and we mistakenly think they are schooling.
 
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HoldenOn

HoldenOn

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My description of schooling is where the whole school moves as a single entity as if they have a telepathic connection. I have seen this several time in the ocean where thousands of fish move in harmony and (seemingly) randomly change direction, but every fish stays in formation. Truly spectacular to watch. Most tropical fish don't do this, or we don't have enough of them in a big enough space. When our fish shoal tightly it is usually because they are stressed or threatened. They huddle together for security and we mistakenly think they are schooling.
I read somewhere that certain fish school like that in reefs to reduce drag.
 

mbsqw1d

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Safety in numbers! Some fish when in the same species do as Sean states, similar to starling murmuration, and that is a school of fish. I think it gives them the appearance of being one large unmanageable fish to an onlooking predator.
 

Colin_T

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Interesting. So you are saying we are keeping schools when we have a group of say 10 tetra, but a shoal when we have some green corydoras and bronze corydoras mixing.
yes.

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My description of schooling is where the whole school moves as a single entity as if they have a telepathic connection. I have seen this several time in the ocean where thousands of fish move in harmony and (seemingly) randomly change direction, but every fish stays in formation. Truly spectacular to watch. Most tropical fish don't do this, or we don't have enough of them in a big enough space. When our fish shoal tightly it is usually because they are stressed or threatened. They huddle together for security and we mistakenly think they are schooling.
A lot of freshwater fish do move as one in the wild, but you need lots of them and a big environment and a predator. This doesn't happen in captivity because most people don't keep a thousand neons in a swimming pool with an Oscar.
 

AtomicFish

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A good example is Cherry Barbs. Now this fish at least in my tank all 5 of them swim pretty close together most of the time all though they will go all over from time to time in there own directions.
 
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