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Sunday, 4 September 2016

Have we got newts for you?

Monday 29 August dipping at the new flood relief channels, Riverside Valley Park
The quick answer would be nope, we didn't find any newts.
Net gain: pondlife enthusiasts dip in 

Possibly the new channels are just too new for any newt population to have re-established itself yet. We used to run this event annually over several years, recording numbers of palmate newts, water scorpions, sticklebacks, dragonfly, damselfy and mayfly nymphs, and the occasional water measurer and eel.

In addition to being still quite bare, yet to develop more mature bankside and floating- leaved vegetation, the newly re-formed channels (see post 'Joy of Exe' Mon 26 October 2015 about the larger flood relief scheme) flow much more quickly, shallowly and clearly, as opposed to being deeper, standing water. It might suggest we were in for a long afternoon. 

But the first nettings proved otherwise, with abundant water boatmen and water snails. These seemed both numerous and quite small sized, new colonisers moving in to the new habitat.  
Spot the freshwater minibeasts ... they are in there somewhere

As the tray contents settled, more species were found with successive dips: Daphnia water fleas, water slaters, midge larvae, freshwater shrimp Gammerus, a gelatinous glob of snail eggs. A stick turned out to contain a Caddis fly larvae. Most of these feed on vegetation or detritus, quite sparse in the new and constantly flowing channels. We also found several freshwater leeches (probably Erpobdella octoculata, with its 8 eyes and mottled coloration), a minnow, and a planarian flatworm, from the different ventral and dorsal colouring Dugesia polychroa, with its amazing orange eye slits and partial shapeshifting. Despite the flow, there were also a few pond skaters skimming over the surface.
Brown and sticky. With a caddis fly inside
As to what could be supporting such proportions of predatory species ... a pond, or a freshwater channel, is a bug eat bug world, where survival is of the biggest, the fastest growing, or the best at hiding. 

Interestingly while most of minibeasts in the newest channel were early stage, mobile or fast-developing species, some of the other deeper, more established and weedier channels with still water contained other species, such as sticklebacks, damselfly nymphs, and a dragonfly nymph (likely one of this year's Broad-bodied-chasers Libellula depressa), in the early stages of accumulating its cladding of algae.

Around the watercourses themselves were a few other terrestrial species to spot amongst the emerging vegetation: a Common darter dragonfly basking on the open ground, a Rusty dot pearl moth Udea ferrugalis, and the telltale woven together leaf blade of a Clubionid spider.
Ruddy for action: Common darter dragonfly (photo: D Ireland)

Who lives in a web like this? Probably a Clubionid spider

Rusty dot pearl moth dropped by

By the end of our allotted two hour survey event slot, we had gathered a useful species list. The value is in regular monitoring, to build up a picture of the species assemblage and any changes over time. We'll be back; no newts today; but next time....

With many thanks to Matt, Nicky and Dave for help on the day.

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