To end this 🧵on the Wensum at Ringland, a glimpse of my drift back downstream in golden rays of the sinking sun, over rippling ribbons of Unbranched Bur-reed & Arrowhead, disturbing a lurking Pike (Esox lucius). Hoping this river stays safe from any road building. #rivers #fish #norfolk 14/14

Above the water Banded Demoiselles sparkled, while below Caddisfly larvae trogged about in their mosaic cases. Sad signs of #invasivespecies Signal Crayfish (Pacifastacus leniusculus) & even more worrying, could these be legs of Chinese Mitten Crab (Eriocheir sinensis)? #riverflies #rivers 13/14

The River Wensum is a #chalkstream rich in molluscs, as can be seen by the drifts of shells including tiny pea clams (Euglesa), big Duck Mussels (Anodonta anatina), Great Ram's-Horn (Planorbarius corneus) & Lister's River-Snail (Viviparus contectus). #MolluscMonday #invert #snailsky #snails 12/14

Under stones were snails: River Nerite (Theodoxus fluviatilis) & the eggs of ?Common Bithynia (Bithynia tentaculata). Still mystified by the abundant jelly loops (see also vid in 1 above), some 30 cm long. AI suggests they are Northern Caddisflies (Limnephilidae) egg masses. Really? #invert 11/14

Arrowhead (Sagittaria sagittifolia) is a dominant macrophyte in the Wensum & there's a bit of Spiked Water-Milfoil (Myriophyllum spicatum). On the banks Common Club-Rush (Schoenoplectus lacustris) austerely stands sentry, while Great Willowherb (Epilobium hirsutum) gives pink flamboyance. 10/14

Besides Fan-leaved Water-Crowfoot (Ranunculus circinatus) it was good to see a sprig of another Water-Crowfoot but I'm not sure which species. Also some nice Water-Starwort (Callitriche) possibly of two species. #wildflowerhour #flower #norfolk #norwich #rivers #macrophytes #chalkstreams 9/14

In the shallows of the River Wensum at Ringland there were some tiny plants of Curled Pondweed (Potamogeton crispus). Also some Perfoliate Pondweed (P. perfoliatus) & one stand of Fennel Pondweed (Stuckenia pectinata). #wildflowerhour #flower #norfolk #norwich #rivers #macrophytes #chalkstreams 8/14

The dominant macrophyte of the Wensum at Ringland is the Yellow Water-Lily (Nuphar lutea), in full glorious bloom last week, spangling the river with golden nuggets, some already bearing their "brandy bottle" seed pods, above forests of their giant lettuce-like leaves. #wildflowerhour #flower 7/14

The River Wensum has the usual sad array of green #algae: Blanketweed (Cladophora glomerata), Gutweed (Ulva intestinalis) & Water Felt (Vaucheria), indicating eutrophication, the #invasivespecies Nuttall's Waterweed (Elodea nuttallii) & the more welcome Willow Moss (Fontinalis antipyretica). 6/14

The Wensum at Ringland also has European Perch (Perca fluviatilis) while Mute Swans patrol the river. Many people were enjoying it in flotillas of SUPs, kayaks etc, as the air soared to 34.1°C, the water barely cooling at 22.4. Though water was clear, the river clearly suffering excess silt. 5/14

Chabot Bullhead (Cottus perifretum) & Common Gudgeon (Gobio gobio) inhabit the clean sands & gravels of the Wensum at Ringland as #rivers of European Minnows (Phoxinus phoxinus) accompanied by plentiful Common Dace (Leuciscus leuciscus) criss-cross the water column of this chalk stream. #fish 4/14

As with my previous swim, 5 years ago, in the Wensum at Ringland bsky.app/profile/nume..., amazed at high numbers of European Chub (Squalius cephalus) compared to any other river I've been in. Fewer Common Roach (Rutilus rutilus) except the gathering of big ones under the tree. #fish #rivers 3/14

The biggest Chub (Squalius cephalus) I saw in the River Wensum at Ringland was actually not in the congregation but out on its own in the main channel, among the highest density of Chub I've ever seen. A few have lumps on their bodies, perhaps from the Cnidarian parasite Myxobolus pseudodispar. 2/14

Burwell Lode was a cool 18.5°C while the air was 30.3°C. Despite wearing a wetsuit, contracted my 1st Swimmer's Itch case of the year (on my face outside mask); larvae of the Schistosome parasitic flatworm (trematode) Trichobilharzia franki had burrowed into my skin. Also found a body board! 12/13

Besides water boatmen (Sigara lateralis), surprise to see a Scarce Chaser (Libellula fulva) presumably from Wicken Fen, along with steady stream of Black-headed Gulls. Mute Swans were making the poor visibility worse. Given its chalk spring origins, visibility should be good. #birdsseenin2026 11/13

Some sculptural stands of air-bubble bejewelled Fennel Pondweed (Stuckenia pectinata) persist in Burwell Lode, along with some tattered remnants of Perfoliate Pondweed (Potamogeton perfoliatus) and of course, Arrowhead (Sagittaria sagittifolia). #Wildflowerhour #rivers #cambridgeshire #nature 10/13

While the banks of Burwell Lode are fringed with Reed Sweet Grass (Glyceria maxima), surviving the green algae is Whorled Water-Milfoil (Myriophyllum verticillatum), Rigid Hornwort (Ceratophyllum demersum) & perhaps Common Mare's Tail (Hippuris vulgaris). #Wildflowerhour #rivers #cambridgeshire 9/13

Among the plants that suffered from clearance, and were mostly only found in the reach of Burwell Lode that had been left, hopefully deliberately, as a refuge for fish and other life, were Fan-leaved Water-Crowfoot (Ranunculus circinatus) & Yellow Water-Lily (Nuphar lutea). #Wildflowerhour 8/13

Apart from the plant clearance, Burwell Lode, a 5km canal flowing from Burwell to the River Cam at Upware, originally an industrial shipping lane dating back to the 17th C, suffers eutrophication with dense growth of green algae: Gutweed (Ulva intestinalis), Cladophora glomerata & Vaucheria. 7/13

This is what much of Burwell Lode, a chalk spring fed canal, looked like at the start of July; brutally stripped naked of macrophytes below the water, with remnants of the rent vegetation scattered on the surface. I also twice got tangled in abandoned fishing line. #rivers #cambridgeshire 6/13

In the vegetated refugia in Burwell Lode it was lovely to see quite a few Silver Bream (Blicca bjoerkna) as well as Common Gudgeon (Gobio gobio) & Threespine Sticklebacks (Gasterosteus aculeatus), including a dead one of the latter that was also another victim of the vegetation clearance. #fish 5/13

The refugee fish packed in the one remaining vegetated reach of Burwell Lode, included some reasonable size Common Roach, some infected with the Cnidarian parasite Myxobolus pseudodispar, as well as some fry & occasional Common Rudd (Scardinius erythrophthalmus) & European Chub. #fish #rivers 4/13

In Burwell Lode where the vegetation hadn't been destroyed, besides Dace, Bleak were busy feeding at the surface. Could the #fish below be the #invasivespecies, Sunbleak (Leucaspius delineatus)? Not sure I've ever seen it before except perhaps in the Lark bsky.app/profile/nume.... #Rivers 3/13

As we got in Lode at Burwell, puzzled how few #fish, apart from scared Perch. Contrast to our experience of the Lode at Upware end where it can be like a fish-packed aquarium bsky.app/profile/nume.... Realised: vegetation clearance including killing this Perch. Where plants left, Dace appeared. 2/13

Maiden Pink (Dianthus deltoides) #StillFlowering at usual place at West Stow, but very stunted, and most of the surroundings dried to a brown, desert crisp. #WildflowerHour #Suffolk

🙏 Usually use iNaturalist but as this Water-Lily Reed Beetle (Donacia crassipes) from Cut-Off Channel, Stoke Ferry is nationally scarce thought I'd add to iRecord. 15 mins of my life I'll never get back! Thought how do people manage with such a clunky system, but seems I was judging it unfairly...

To end this 🧵the star-spangled River Wissey 10 days ago, when the air was a mere 32°C and the water a cooling 20.5°C (although at 20 degrees it no longer counts as cold water swimming!). Even a coral reef or Mediterranean sea cannot generate more joy in this river snorkeller. #rivers #norfolk 23/23

Here are two quite big Brown Trout, mirrored on the surface, in a sandy pool of the River Wissey, then a small & medium trout hanging out together beneath a little waterfall; often small trout seem to seek protection beside bigger ones. #fish #rivers #norfolk #trout #browntrout #chalkstreams 22/23

The River Wissey is full of history; bottle maybe 80-130 years old from the Victorian or Edwardian eras, horse shoe potentially 70-140 years old likely from a heavy horse & the lower jaw bone of probably a calf, maybe iron age (thanks for help with ID @timholtwilson.bsky.social & Sam Dunnett). 21/23

Here too are strands of the green #algae Cladophora glomerata, indicating that the River Wissey is eutrophicated, likely by agriculture & sewage. But there is also the healthier indicator, in the faster flowing reaches, of brown algae Frogspawn algae Batrachospermum & fluffy green Vaucheria. 20/23