Christmas CRIMP

When is the best time to go wading in a river? That's right, WINTER!

 

 

There's more life in here than meets the eye!

The last riverfly survey before Christmas was indeed a very chilly one. The river was a lot higher than usual due to the heavy rains recently but that didn't stop us from catching some cool beasties! I've caught a couple of brown trout parr on the odd occasion like the little guy below, however I've never had a stickleback land in my net, never mind two of them!

Brown Trout parr

Three-spined Stickleback Gasterosteus aculeatus

Sticklebacks are common in UK rivers and ponds, usually reaching a length between 4-7cm and living for up to 3 years. They are unusual in that they do not have scales on their body like most fish, but instead have bony armour-like plates, as well as the characteristic spiny protrusions on their backs. Sticklebacks are normally schooling fish but during the breeding season in the spring the males become very territorial and develop a red patch under their belly to advertise their dominance over other males and to attract a female. The male also takes on parental care duties, building a nest using bits of weed, chasing rival males away, and ensuring that the eggs are well oxygenated once the female has laid them. Once the eggs have hatched he will capture any fry that try to escape by sucking them into his mouth and depositing them back in the nest. He will do this until the young are big or strong enough to escape him!

We also caught some familiar faces in the form of pea mussels, pond snails, and various leeches. Leeches can survive in a wide variety of freshwater bodies including those with low dissolved oxygen which may indicate polluted waters. However as we are also regularly finding large numbers of blue olive mayfly, flat bodied upwing, caddis and stonefly larvae which are all very sensitive to pollution, we can assume that this river is healthy for Christmas. Yay!

Leech, possibly Erpobdella sp. next to a flat bodied upwing larva