Dis-guising water beasts!

Preparing a spooky disguise this Halloween? Did you know that, in our celebrated rivers and lochs, there are many animals that also like to use camouflage at this time of year? Some are even quite gruesome! Find out more about what lies hidden below the surface in the Year of Coasts of Waters.

Lamprey use suckers and rasping teeth to feed on other fish.

There are an array of animals that use our rivers, lochs, and ponds for their hidden early life stages and only really reveal themselves when they reach adulthood.  One occasionally gruesome fish that lives concealed in our rivers is the lamprey.  Lampreys are particularly primitive and unusual fish which have a long larval stage in our rivers. Right now, juvenile lamprey will be living as blind, filter feeders hidden within silt beds on the margins of rivers and backwaters.  But by next spring some of them will have transformed into eel-like adults. 

Their adult mouths are a disturbing sight, with circular arrays of teeth to suck blood and fluids for their meal!  The adults search for other fish and, when they find the right one, attach themselves with their sucker-like mouth and get a quick meal.  Sea and river lamprey both feed when they migrate down into the sea.  But our Loch Lomond National Nature Reserve hosts a unique river lamprey population that, instead of going down into the Firth of Clyde, only feeds on the fish populations that live in Loch Lomond.


A large number of riverflies also spend most of their lives on the beds of rivers and lochs.  The best known riverflies are perhaps mayflies which grow, largely hidden, underwater as larvae for a year.  During this time you may see them in the bills of dippers, which like to feed on them in fast flowing streams.  Or you might more commonly see versions of them as ‘flies’ that fishermen often use to catch trout or salmon.  However mayflies shake off their shy and hidden nature right at the end of their unique lifecycle, when their adult stage emerges for only about 24 hours.  As their name suggests, this happens during the month of May, when they famously ‘dance’ above the water to attract a mate, and then lay their eggs.

Our riverflies also provide a vital source of food for several fish species in our rivers and lochs.  Again, they are often hidden well below the surface at this time of year. The most famous of our fish species is the Atlantic salmon.  As juveniles they live largely hidden in our rivers feeding on riverflies and other insects.  But the adults will just be finishing their amazing migration up to their spawning grounds in many of our rivers, having travelled from feeding grounds in the North Atlantic.  They are most obvious when they briefly leap clear of the surface as they battle up waterfalls.  They will soon begin spawning and their backs can sometimes be visible when they spawn in shallow gravel areas.

Atlantic salmon

Find out more about freshwater life and how to visit our National Nature Reserves where you can find many of our freshwater species.

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