It’s September!  This means that it’s time for everybody’s favourite time of the year – back to school!

Okay, so, maybe not everybody loves back-to-school time.  But for a lot of our fish, their “school” is the happiest and safest part of their lives.

A school of fish is most accurately defined as: a group of fish that swim together in the same direction. Fish that group for social purposes are technically shoaling, and groups of fish often switch back and forth between both.

For something that appears so simple, it’s actually an incredibly complex behaviour. Scientists don’t fully understand the ins and outs of it yet, but the fact that it’s so common means it must be advantageous.  Schooling can increase feeding efficiency, make it easier to find a mate, and let the group as a whole navigate better than an individual.  Some scientists believe that traveling in a school may reduce drag or resistance, similar to a flock of birds.  It’s also quite an effective predator-avoidance technique – safety in numbers, right?  Schooling behaviour can confuse hunters, and lower individual risk of predation.

One of the flashiest exhibits at Ripley’s Aquarium of Canada is the alewife exhibit, located at the entrance to the Canadian Waters gallery.

In-house, it’s referred to simply as “Schooling”, and it’s easy to see why.  This is a monospecific exhibit, meaning it has only one kind of animal.  Alewives are anadromous, which means that in the wild, they are born in freshwater and live most of their lives in the ocean (sort of like salmon).  They’re close cousins of herring, and there’s some evidence that they communicate with farts!  But the first thing you’ll notice is that it’s a huge group of animals, all swimming together.  How many fish do you think there are in there?  Go on, take a guess.

Some fish, like alewives, are what we call obligate shoalers. This means that they spend their entire lives in a group.  With obligate shoalers, being alone or in a too-small group can cause a measurable stress response.  That’s part of the reason why we have such a large school here at the Aquarium – they won’t be happy or healthy otherwise.  If you’re looking at the alewife exhibit, watch out for any that get separated from the main group.  They zoom back in in quite a hurry!  You’ll be able to see the school swimming together against the current in the exhibit, and moving up and down in the water.  If you’re lucky, you might get to see a feeding, when they’ll all rocket to the surface together.  These fish usually have a very fast response time during feeds.  Many eyes mean someone is likely to spot the food as soon as it goes in.

While the alewives are certainly an obvious example, make sure to look for schooling and shoaling behaviour in the other exhibits as well!

Our Swarm: Nature by Numbers exhibit has more information about group behaviours in animals, and lots of other examples of animals that swarm, shoal, and school together. Make sure to check it out!

Oh, and to answer the question above? We have almost 7000 individuals in our alewife school!


Have a question about the Aquarium, or something you would like to see on Deep Sea Diary? Drop us a line in the comments below for the chance to be featured in our monthly Q&A post!


Hannah is an aquarist in the Canadian Waters gallery, where she’s currently the primary caretaker for the Alewife, American Eel, Lobster, and Sea Pens exhibits. She double majored in Marine Biology and Oceanography at Dalhousie University in Halifax, where her Honours research involved social animal behaviour, though she’s downsized from whales to fish. When she’s not at work, she likes to hang out with her pet rats, read and write, play Pokémon Go, and eat All-Dressed potato chips.

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