Congratulations! This year, you have been lucky enough to have trout in your classroom. The tank was set up before Christmas and 100 eggs delivered in January, so what next? Well now it is up to you to take care of your new classroom friends and nurture them from egg to fry. See the video below for Neil and Christi’s egg introduction presentation.
CHALLENGE – Once your trout have hatched, it is your job to name them all. There is a catch though: all the names have to begin with the letter ‘T’. This is called alliteration. Each trout will have their own character, just like each pupil in your class, and you can base their names off this if you like. What might you call a trout that races around the tank and is always bouncing off the sides? How about Turbo? What about a trout that is quite shy and stays near the bottom? Could that one be called Timid? Or maybe you know a very shy person called Trevor and decide to name your shy trout after him. As a class, keep a list of all the names you come up with.
Important things to remember:
- Check the temperature every day – the water should be no higher than 10°C for the first few weeks.
- Remove dead eggs when you see them (a teaspoon and net are good tools for this).
- Wash your hands with water only if doing anything in the tank, then wash your hands with soap and water afterwards.
- Once your fish are swimming up and looking for food (in the fry stage), feed them twice a day. Only feed them a small amount – one small pinch will do.
As you can see from the video below, your Trout are still at the Alevin stage and are very happy to stay in their Redd.
The Alevins have everything they need as they are still getting food from their yolk sac, the orange bulge on their under belly.
As this diminishes they will begin to look more like a fish and will soon be Parr.
It will probably be next week before this happens. They will begin to leave the Redd in search of food and instinct tells them to look up to the surface, this is when we can start to introduce food.
Next time we look at when, and how, to feed the Parr.
Neil and Christi
24/02/2021: Swim bladder
Today’s key word is buoyancy, which is the ability of an object to float in water or any other fluid.
Your trout are now entering a critical stage as they transition from Alevins to Fry. They have almost depleted their Yolk Sac and hunger will soon force them from hiding on the bottom to swim up to look for food.
At this time, your Trout are heavier than water and would struggle to maintain a position in mid-water however, they have a clever way of overcoming this, the Swim Bladder (see diagram below). The Swim Bladder acts as a balance to help the fish maintain ‘Neutral Density’. This makes it easier for the fish to swim freely between different layers in the water.
Not all fish have Swim Bladders, particularly bottom dwelling fish, as being heavier than water is an advantage for them.
The Swim Bladder is like a small balloon within the body cavity of the fish and contains a gas, usually air/oxygen. At this stage, your Trout need to inflate their Swim Bladder to enable them feed easily off the surface, where the food will be. The Fry achieve this by swimming to the surface and taking a gulp of air that inflates their Swim Bladder.
Only when your Trout are swimming up in the tank can you begin to feed them with a tiny, small, miniscule, pinch of food. If, after 5 minutes, there is still food on the surface, you have given them too much. If all the food is eaten, you can try giving them a little more.
Neil and Christi
Click on the image below to learn more about the swim bladder and how it works by doing your own experiment!
Go through the worksheet above then watch this video to see Christi and Neil run through the swim bladder experiment:
For the Teachers – click on the cover below to open the teacher’s guide and troubleshooting document: