Stream Dipping in Gillfield Wood 31 July 2022

 

If you go down to the Brook today......

 

Friends of Gillfield Wood’s stream dipping event was due to start about 1pm in Totley Brook. Nell Dixon, our Sheffield CC woodland ranger, myself and another ranger arrived around noon with the clear expectation of rain. Well, that’s it, we thought, people are not going to show up this year as the weather is unsettled and wet. The water level in the brook had improved with the recent rains and was flowing nicely but not too deep, probably 6 inches on average.

 

Then the weather began to slowly improve. The first family appeared around 1:30pm. And gradually a few more people turned up. We started handing out the nets and containers, then introduced youngsters to stirring the gravel and stones allowing the water to wash any invertebrates into their nets. More families joined us… and more, and in no time at all we had 24 children excitedly dipping to see what they could find. 

 

The children were really pleased with their discoveries with obvious delight in seeing fish, our largest mayfly and the extremely unusual Horsehair or Gordian worm. The latter is the free-living adult stage of a parasite which can use a variety of hosts, some of which are land invertebrates.

 

Here is a list of fish and invertebrates that we found. Some only have scientific names (shown in italics) or common names that apply to a whole group of similar animals.

 

Fish:

Trout - very young

 

Bullhead (Cottus gobio) including a number of sprats. Children often think these are tadpoles due to their large heads, but tadpoles are found in ponds not streams.

 

The mayflies, stoneflies and caddisflies are indicators of a healthy stream. Names in speech marks are often used by fishermen.

 

Mayflies - 4 families

Heptogeniidae: Flat-bodied mayfly (Ecdyonurus species)

 

Leptophlebiidae: Prong-gill mayfly (Habrophlebia fusca) 

 

Ephemerellidae: ‘Blue-winged olive’ (Serratella ignita)

 

Ephemeridae: ‘Green Drake’ (Ephemera danica) our largest mayfly. It likes to burrow in the mud & gravel awaiting its prey with its large projecting mandibles.

 

Stoneflies - 1 possibly 2 families

Leuctridae: ‘Willow or Needle flies’ (Leuctra species)

 

Possibly Chloroperlidae – small specimen & difficult to see the necessary identification features.

 

Caddis flies - 3 families

Rhyacophilidae: ‘the Green Sedge’ (Rhyacophila dorsalis). This caseless caddisfly has gills on the side of their abdomen. They are our only predatory caddisfly.

 

Sericostomatidae: Bush-tailed caddis (Sericostoma personatum)

 

Limnephildae:  Pupa of some - most common Caddis family

 

The invertebrates below are less likely to be found in a healthy river but are always around in a few numbers

 

Water Bug – some live on the surface such as Pond Skaters. Others live below the surface such as Water Scorpions. In Totley Brook they are only found in very slow sections forming pools at the edge of the stream.

Veliidae: Water Cricket (Velia caprai) - like a small pond skater with shorter legs.

 

True Flies – 3 families were found in their larval form.

Craneflies: Dicranota species (Pediciidae) and Tipula species (Tipulidae)

 

Dixidae: Meniscus Midges (Dixa species)

 

Additional finds

Water mite – looking just like their terrestrial representatives.

 

Gordian worm - not a true worm (Nematomorpha). Also called horsehair worms. They are unsegmented having a smooth body up to 20cm long and only 1mm wide. Rare.

 

Glossiphoniidae: Leech (Glossiphonia species). They have 6 eyes arranged in pairs in a line down the front of the head. Some of these look after their eggs and young which most people would not expect of a leech.

 

Gammaridae: Freshwater shrimp (Gammarus species)

 

Sialidae: Alderfly larva – (Sialis species). This is an invertebrate with a long evolution of some 200 million years. They are predatory and breath through 7 pairs of jointed gills. You might think these were more legs but only the front 3 pairs are true legs.

 

Snail - Jenkin's Spire Shell (Potamopyrgus antipodarum). This came from New Zealand about 150 years ago. They have travelled across most of the country via waterways.

In all this was an excellent day with many families attending and gaining a lot of pleasure from the experience, both children and adults. If you missed the opportunity or would like to see this event run again, please do let Friends of Gillfield Wood know by contacting fogwsecretary@gmail.com

 

Paul Hancock

Coming Soon (see Events page and Conservation Work page for further details):

    

Tuesday 16 May: Flora Walk

 

Saturday 20th May: Bird & Butterfly Walk 

 

Friday 30th June: Swift watching