Hogsmill Electrofishing





Over the last two days members of the Environment Agency have been undertaking fish surveys at four locations along the Hogsmill. This is from Hogsmill Lane (just off Villiers Road) to Oakland Way-Chamber Mead KT19 upstream, just  across the borough boundary.

This type of survey is  usually undertaken by boat - although backpacks were used in the shallows upstream at Ewell. Circular electrofishing 'anodes' attract the fish, which swim towards the the charged equipment, where they are stunned but not harmed. They are then decanted to large buckets for further examination or 'processing'.

During the initial survey  at Elmbridge Meadows, a surprising catch of ~100 fish was made in the first of three runs. This is virtually one fish every metre of the ~90m netted area and included: chub, dace, roach, stone loach, gudgeon, stickleback, minnow, bullhead and an eel.

At  Worcester Park Road-Tolworth  A240  a similar number of fish were caught. By far the majority of the minor species were minnows, which were not located in the Ewell site. A rudd caught at this location was a surprise, as it would be more at home in still water, so had probably been introduced or had somehow introduced itself.



Measuring a rudd


The coarse fish are measured and in some cases a scale sample is taken - presumably for DNA analysis. The minor species are not  measured, although it can  be difficult for an untrained eye to tell them from the many young chub - which are measured - and  demonstrate natural recruitment. No perch were located, although there is a shoal below the gauging station at Watersplash Close in Kingston, so maybe they cannot negotiate the weir.



Silver eel about to return to spawn



eel on eel board Hogsmill lane 
 
Fun and games are averted, as the eels are measured by using a special 'eel board'. This prevents some of the larger animals from thrashing around and aids examination of the condition of the animal. Some were transforming into silver eels; laying down fat for the journey to the Sargasso in the Caribbean where they breed. The eel board facilitates gentle return to the water of the animal without too much handling.





Comments

Post a Comment

Please share your thoughts

Most viewed

Heritage Trees part 2: street trees.

Image
  Oaks and maples Cambridge Gardens 2019   Street trees can often be the most beautiful objects in our streets. They are important to their communities as well as having environmental benefits. They are a living history in our landscape and can have particular connections. They may be fragments of a previous landscape incorporated into a modern street scene, such as the oaks at Cambridge Gardens once  part of the Duke of Cambridge's estate.  A great read with information on how to research street trees is a  History of Street Trees by Dr. M. Johnston.  London plane trees CRE 1976 Beech tree, Chesterton Terrace 1976 Studies show that the difference in local tree cover can reflect the various socio-economic groups. In Victorian times middle class areas were planted with many street trees or had higher quality front gardens than working class districts; now referred to as 'green equity'. It can be demonstrated by looking at old photos of the seven roads that were
Read more

Fishing the Hogsmill

Image
Fly-fishing the Hogsmill   It is interesting to see the river from a different perspective: the Hogsmill is popular with anglers at this time of year; although it is unusual to see someone fly- fishing. A chub has just been caught on bread and it looks a good size. Trout are sometimes seen in the Hogsmill and can sit in the weir notch by the school. Our own Richard Jefferies in his book 'Nature Near London'  remarked on the Hogsmill trout as far up as Tolworth Hall Bridge (now the A240). chub    This fish was carefully unhooked and orientated in the swim where it soon finds it way - probably to the next father and son - sitting further upstream. These anglers have caught the 'ghost' koi within the last two weeks and appear to be the second successful pair to catch the pond-escapee in the last few days. Ghost koi are a British invention. They were produced by accident in the early 80’s when a farmer allowed a mirror carp and a koi to spawn together. The offspring
Read more

Seething Wells: they've done it again

Image
The last day of May, I went to see if I could find the black redstart that had been widely reported, no luck but it will turn up again on one of the old buildings. The lush vegetation was looking beautiful between the Filter Beds at Seething Wells. I made a note of the breeding birds: goldfinches twinkling away, blue tits gathering food, sand martins flying over the FB's (only two this year unfortunately) moorhens and some scruffy little coot chicks entangled in the algal blooms.   Proud parents were showing off their four Canada chicks; they can cover a lot of ground in a short space of time they were soon feeding on water pepper and bistort gleaned from  the ziggerat-sided basins. A song thrush sang from the wharf alongside greenfinches as well as the seasonal chiff chaff; although this year all numbers are down, reflecting not only the topsy-turvy Spring but also the continued tumble in insect numbers (even seed eating birds are dependent on insects to feed their young).
Read more