Recently, the Environment Agency have been working at School Weir along the Sid removing a large bank of river stone – and at the same time they have ‘rescued’ the fish in the pool at the bottom of the weir.
As reported by Ed Dolphin: Busy week for the river, the Environment Agency is clearing the gravel bank at the foot of school weir in the Byes to keep the flood defences working…
The fish were caught using the harmless method of electro fishing, or a pulse sent through the water that stuns the fish. It was done this time last year, as also reported by Ed at the time: Electro-fishing this morning on the main river and tributaries as part of the assessment of the whole catchment of the Sid
As for this year’s ‘catch’, the River Sid Catchment Group reports: Salmon found in the Sid!
Salmon found in the Sid! – I salmon parr, 19 brown trout numerous loach, bullhead, minnows, eels and brook lamprey. were found below School Weir on Monday 15th Sept during the electrofishing carried out before the EA started to remove the stone bank. Thanks to Jon Trevett of Stonbury for sharing the information with us.
Which [as commented on by Ed] means an adult pair will have bred successfully. Let’s hope they will soon be able move up river to their preferred spawning beds.
Here’s Ed’s full piece in the Herald [18th September], talking about new plans in place to help the River Sid’s migratory fish:
The River Sid is a trout river, and hopefully, ongoing work will boost the population and allow more migratory fish upstream for a chance to breed. Maybe we will even see the return of the salmon, which were last recorded in 2019.
In the meantime, the Environment Agency is supporting the local efforts to improve the river. This week, the EA has employed specialist contractors Stonbury to clear the gravel island that is choking the river below the school weir.
Before they began, they took the trouble to move the trout that live in the pool to a safer area. They applied the same electro-fishing technique used last year by the Westcountry Rivers Trust and the River Sid Catchment Group to survey the health of the river’s fish population. An electrode is laid on the bed of the river, and the person doing the fishing has another electrode that releases electric pulses of about 150 volts. This stuns any fish between the two electrodes and allows them to be netted and put into a container. This doesn’t harm the fish, which recover very quickly, to be released into the safer area away from the shingle digger.
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Back in the 1920s, John Tindall studied the nature of the beach shingle and established that the majority of the smaller shingle came down the river from the geology at the upper end of the valley.In years past, when the EA dredged the river, they took shingle down to the beach, thus mimicking the ancient natural process, but they stopped doing that a few years ago.
I’m pleased to say they have started doing that again, and the shingle was spread on the beach by Port Royal. It was rather muddy at first, but the high tides and rain soon washed it.
The river gravel is one key factor for the fish spawning; they create a depression in the river bed called a redd to hold the eggs. Sea trout prefer to lay their eggs in the gravel in the upper reaches of the river, but at the moment, there are too many barriers, and most of the sea trout have to breed in the stretch below the school weir, which depletes what would be the natural balance in the upper river.
Plans are now in place to adjust some of the man-made barriers that block upstream progress for migrating fish trying to reach a breeding site. One thing that can be done is moving some of the rocks in the many weirs from Sidford down to the Byes to create passable channels, but the main barrier is school weir. At 3m, the school weir is just too big even for a salmon to jump.
There are pictures of salmon managing to reach halfway up, but they would have to be like Armand Duplantis to make it over the weir.
There have been many plans to build a way around the weir, perhaps a fish ladder which allows the trout and salmon to take a series of smaller leaps, but to no avail. New ideas are coming forward, and the river current group won’t be giving up.
And here’s Ed following up his piece in the Herald a week later [26th September]. As he says, salmon are still breeding in the river Sid – but it’s not enough:
The good news is that we still have salmon breeding in the River Sid. The less good news is that they are restricted to the stretch in town rather than getting to the upper reaches of the river to their preferred breeding sites.
As I reported last week, Environment Agency contractors were electro-fishing in the river below School Weir to keep fish safe while the gravel was being dredged. I didn’t have the full results by the deadline for the story, but two days later, Jon Trevett sent the details of the catch. Apart from 19 brown trout of average size 30cm, there were numerous loach, bullhead, minnows, eels, 18 brook lamprey, and the big surprise: one salmon parr of 7cm.
A salmon parr is a juvenile fish, the fourth stage in a complicated life cycle. Salmon lay their eggs in winter in a hollow on the river bed, and the female then covers them with more gravel. The babies, or alevins, hatch and stay in the protection of the gravel, feeding on their yolk sac. When this is exhausted, they swim free as 3cm long fry.
By the autumn, the young fish have grown to be what are known as parr, and are beginning bodily changes to cope with the next big change when they leave the freshwater river and swim out to sea to grow to full adults. When the sea-living adults are ready to breed they return to a river, usually the one where they were born, navigating by the Earth’s magnetic field and minute chemical symbols detected in the water.
In years gone by, salmon frequently bred in the upper reaches of our river system, but numbers have declined for several reasons, the size of School Weir is literally the biggest problem. At 3m, it is too big a leap for most salmon.
The presence of the young parr shows that at least some adults have continued to return to the river, and they have found gravel good enough for egg laying in the stretch between the ford and the weir. There is a possibility that they have also been breeding in the area below the ford.
Local fishermen have reported good numbers of migratory sea trout in there, but it hasn’t been electro-fished for parr, and so we cannot tell. Local enthusiasts net fish at the foot of School Weir in October and lift them above the weir, but it is several years since an adult salmon was caught.
The River Sid Catchment Group is putting together a plan to reduce barriers to the migrating adult trout and salmon, and it is hoped that a way around School Weir can be constructed, but complications with flood prevention are proving difficult.
The presence of the salmon, a priority species for conservation, can only help push the project forward.
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