Wow, what a busy few weeks it’s been! Most of the trout eggs have now hatched and all of this year’s pupils have been working very hard to look after their new aquatic classmates. We’ve been impressed by the high success rate of hatching, even if it happened a little sooner than we expected in some hatcheries! The first couple of weeks of development are shown the pics below!
Some of the other eggs have changed shape slightly and you can see the fish curled up inside, ready to hatch.
Once the fish start to hatch, it’s important to keep the water nice and clean. This involves removing any leftover egg shells which can make the water foamy (as a result of protein mixing with the water) as well as using your spare water supply to replace a cup-full of water from the tank every day.
These alevins are one week old. Their bodies are quite pale with a large orange yolk sac attached. At this stage they spend most of the time resting on their sides at the bottom of the tank. In the wild these fish would still be hiding in the redd, so it’s normal if they don’t move around much!
This week, following the February break, we have noticed more changes in both the appearance and behaviour of the alevins. They are starting to darken in colour and are becoming more sensitive to disturbance (you will notice they hide under the stones when the hatchery lid is opened). These changes are all part of their preparation for life outside of the redd. They are still pretty tiny (around a couple of centimetres long), so here’s a close-up picture of some we’ve been looking after in the Clyde River Foundation lab.
We’ll be keeping a careful eye on the over the next couple of weeks. As soon as the yolk sac is used up, the fish need to start feeding on aquatic insects and that means releasing them into a burn. Look out for Release Day updates soon!