Minnows are not common in Harris and they are ofter confused with sticklebacks. They are an 'alien' species recently introduced to Harris by mistake! If you find minnows in Harris do not move them. Instead tell the Outer Hebrides Fisheries Trust
Being small makes minnows a good snack for trout and birds (their predators). To confuse these predators minnows move fast and swim close together in shoals. Fish at the outside of the shoal are in the most danger of being eaten and so all the fish want to be in the middle.
Life cycle and habitat
Minnows are small, most could fit in your hand (they are less than 10 cm). They spend their whole lives in freshwater and like clean, cool water with lots of places to hide. Their shoals often contain over one hundred fish and they eat water fleas and young insects, water plants and rotting scraps. Minnows collect in large groups in the summer and put their eggs in areas where water is always moving like stony river and burn beds and in shallow water along the sides of lochs.
Minnows in Harris
Minnows are common in other areas of Scotland but they have only just come to the Outer Hebrides (they have only been found in one set of rivers and lochs in Harris). They cannot live in the sea and that stopped them from reaching the Hebrides before. Live minnows used to be put on hooks by fisher men and women to catch bigger fish. Sometimes minnows wriggle off hooks and in this way they may get to new places. We are worried about minnows spreading because they might change the animals and plants in our freshwaters. They could also replace trout and salmon which locals and tourists like to catch.
Minnows like to eat the same things as young trout and salmon. In Harris where there is not much food for fish, minnows might steal the food and hiding places that young salmon and trout need. Minnows also eat the eggs of other fish like trout and charr. Small fish like minnows are difficult to remove from a place once they have arrived because they slip through nets, hide under stones and make millions of tiny eggs.
by Katherine Ross