Many people (myself included) tend to use the terms "school" and "shoal" somewhat indiscriminately without thinking too much for the difference between them.

However, I happened to come across the scientific definitions while reading.

The below information was gleaned from Fishes, An Introduction to Ichthyology Fifth Edition by Peter B. Moyle and Joseph J. Cech, Jr.



The distinction is necessary because experiments have shown that schooling is just an extreme example of many shoaling behaviours. It is important also to note that fish shift in and out of schools on a regular basis.

A shoal can go from the classic grouping of fish into an amorphous mass in a matter of seconds. The stimulus for this is a change of activity from travelling, feeding, resting, or avoiding predators. The shape of a shoal can vary widely depending on activity and type of fish; fast moving shoals typically assume a wedge shape whereas feeding shoals are more or less circular.

Shaw (1978) estimated that 25% of fish shoal throughout their lives and that approximately half of all fishes spend at least part of their lives shoaling. In many commercial species the largest shoals are formed when a number of smaller shoals merge. Radakov (1972) mentions “chains” of shoals of migrating mullet (Mugil)in the Caspian Sea that were 100km long! Radakov further noted that in the North Atlantic, herring shoals can occupy 279 million to 4,850 million cubic metres with a fish density of 0.5 to 1.0 fish/cubic metre

How do fish school?

Schooling requires precise sensory contacts among individuals within the schools. The fact that most schools (but not shoals) disperse after dark indicates that vision plays an important part in schooling. Laboratory experiments with temporarily blinded fish support this, but also show that other senses are used. It is believed that the lateral-line system (seeing as it is so sensitive to the movement of water) also plays an important part in ensuring the fish in a school maintain their spacing. It is also believed possible that sound or pheromones play a part but at this time there is no evidence to support this.

Why do fish shoal?

Landa (1998) argues that the combined benefits of the below benefits of shoaling provide strong selective incentives for fish to join shoals.

1) Increased Hydrodynamic Efficiency
This applies mainly to schooling fish and is appealing both because of the regular spacing of fish in schools and because shoals tend to be uniform in size (Hoare et al. 2000). However, laboratory experiments have not shown the positioning of fish in schools to gain any advantage from the hydrodynamic lift created by their neighbours (Pitcher and Parish 1993) though it is still believed that this is the case in the wild. Landa (1998) argues that the leadership of a school is always changing, because while being immersed in a school incurs hydrodynamic advantages to individuals, being the leader of a school means you are the first to food.

2) Increased Efficiency of Food Finding
The reason for this is the presence of many eyes searching for the food. Fish in shoals “share” information by monitoring each other’s behaviour closely. Feeding behaviour in one fish quickly stimulates food-searching behaviour in others (Pitcher and Parish 1993)

3) Increased Reproductive Success
Little energy has to be expended to find a mate within a shoal. Also, for migrating spawners that travel long distances it is more likely that the average direction taken by a shoal is better than one taken by a single migrating fish.

4) Reduced Risk of Predation
This comes in two main interacting ways: dilution, and confusion (Pitcher and Parish 1993). The dilution effect relies simply on safety in numbers (Pitcher and Parish 1993). In any given attack, a smaller percentage of a large shoal will be eaten compared to a small shoal (Major 1978).

The confusion effect is based in the common observation that shoaling fish tend to get eaten mostly when they have been separated from the shoal. Shoaling fish are the same size and silvery, so it is difficult for a visually oriented predator to pick an individual out of a mass of twisting, flashing fish and then have enough time to grab its prey before it disappears into the shoal.

There is plenty more in the book on this subject (begins on page 192) and also in Biology of Fishes by Carl E. Bond (Second Edition).

Andy

Ok, so when I'm looking at a clump of fish in the ocean darting around like one huge mass, they are shoalling?

If they are acting as one polarised synchronised mass, then they are schooling. If they are just "hangin out" together, chances are they are shoaling.

Good to know! I ever knew what the difference was, thanks for the info

I hate to bump myself, but it took a little while to research and write, so I'll give it another shot at life

I was wondering why this thread sank to the bottom so quickly!

I think this is wonderful info to have! I had always assumed that the difference between the to had more to do with the UK preferring shoal, and the US preferring school.

And now I know that seals and the like so after schooling fish (not shoalling) to get food!

It's nice to know! I always used the term "schooling" just because it's what I'm used to hearing ^^

Awesome! Thanks a ton for the Information. That clears a lot of things up.

There's a lot more info in the references and the main book (I tried to make sure I wasn't plagurising...).

It's one of those things you don't realise until you come accross it.

IIRC there are times when a school can develop into a pod. I think that refers to a giant bait ball, but am struggling to find any real information on it.

Anyone know?

Pin it...

I don't know how I missed this when it was new back in August. It is good information. I guess schooling fish were actually the inventors of an Olympics event....synchronized swimming.

I'm going to pin this in TCC FAQ as it's quite handy.

So, from my observations of my loaches...clowns are schoolers, queen botias are shoalers. I have one clown (after mine all died within days of each other a little over a year ago). He *tries* to school with the botias but they scatter willy nilly and it confuses him It's sad AND hilarious.
*No, I'm not getting more clowns anytime soon, maybe someday. He's been alone for over a year, they treated him like dirt anyway.

From the reading I've done I would be surprised if we see any true schooling behaviour outside of the wild or public aquaria. That's not to say that the species that we have do not school in the wild, but I would be surprised to see a polarised amorphous shoal of fish moving in an almost unison that makes the group appear as one larger being.

My neons regulary school, come and watch them some time, as per your definitions


2) Increased Efficiency of Food Finding
The reason for this is the presence of many eyes searching for the food. Fish in shoals “share” information by monitoring each other’s behaviour closely. Feeding behaviour in one fish quickly stimulates food-searching behaviour in others (Pitcher and Parish 1993)

-I can drop a little food down one end of a tank, one or two fish find it and start feeding, the rest of the neons observe their peers feeding and quickly feed as well "school feeding" by the above definition

4) Reduced Risk of Predation
This comes in two main interacting ways: dilution, and confusion (Pitcher and Parish 1993). The dilution effect relies simply on safety in numbers (Pitcher and Parish 1993). In any given attack, a smaller percentage of a large shoal will be eaten compared to a small shoal (Major 1978).

-not seen on such a grand sacle as in the open seas but still possible, any time a large fish shows threatening behaviour the neons immediatly bunch together for saftey, or school as defined above for "dilution, and confusion"




I would be suprised as well, as fish do not schoal as already exampled by you above that to appear as a larger being they schoal for social aspects and that can consist of some distance if cories are watched for any period. If you actually meant the schooling aspect I'd be supprised here as well as they dont do it to appear as one larger being. (although I have read some childrens books that say otherwise )


While in aquarium keeping we gererally do not see things to the same scale as in the wild, if kept correctly we should still see most if not of their "normal" behaviour just on a smaller scale.

Andrew

This post has been edited by Katchan: Jan 7 2006, 11:13 AM

Those reasons you have quoted are for shoaling in general, not schooling in particular. I doubt you will see the neons school. If they did you would see them moving as if they are one large organism. When the group of neons are startled (by another fish or by you) they will scatter in a random manner decided by the individual fish, rather than following a specific pattern as if it were one large mind controlling all of them.

While I was aware of the technical difference, my experience of writing for British and American magazines supports your assumption. Whenever I have used 'shoaling' in an American publication it's been changed to schooling, with 'shoals' being used by Americans to refer to piles of pebbles or sand in streams. American readers get confused when 'shoal' or 'shoaling' is used for groups of fish. British readers seem to use both without any bother.

Presumably American ichthyologists known the difference, though!

Cheers,

Neale

The way i learned is that in basic terms a school of fish is a group of fish all traveling in one direction for a purpose, whether that be moving to feeding grounds or a mass migration. A shoal of fish is a group of fish gathered in one place but not facing in any particular direction or for any purpose other than the company of their own kind.