Join us for the next part of the Salmon’s Tale! In this blogging series by DCRT trustee Chris Firth, follow Salmo the salmon smolt as he travels from the River Don’s headwaters to the low, meandering reaches of the river. Learn which fish species inhabit the three different reaches of the Don and pick up some of the history of the Don along the way…
Salmo had reached the outskirts of Sheffield and everything he once knew was changing. The clarity of the water was no longer the crystal clear condition he had enjoyed in the upper river and the taste and scent were very different. As he dropped further down the river he felt unnerving vibrations and noises rumbling through the water. The bank side vegetation had been replaced by high stone walls, with strange objects moving along the tops of them. The only thing which was consistent were the fish species he encountered. Trout and grayling were in abundance down here darting in and out of the bright green weed which stretched in long ribbons across the surface. He felt safe tucked under this weed but his sanctuary was short lived. Suddenly, without warning, a trout came hurtling past pursued by a large brown creature which expertly grabbed the fish in its mouth and swam up to the surface. It quickly carried its struggling victim to the river’s edge, before disappearing into the bankside vegetation.
This event prompted a desperate urge to keep up his descent. He had been coming upon an increasing number of the walls which stretched across the river but in most cases these had sections cut out of the top which enabled him to drop down into the pools below without much delay. He was now reaching the downstream outskirts of the city and having just descended a particularly large obstruction, noticed a large flow of water entering. This inflow almost doubled the flow of the river and had a particularly unusual taste and smell which he found rather distasteful. Nevertheless, within this flow were hundreds of small fish, very similar in size to himself. They were silvery in colour with slightly orange coloured fins, and appeared to be feeding on small particles in the flow. As he passed through this shoal he also noticed, on the fringes, a number of much larger fish drifting backwards and forwards. These were powerful looking and were clearly attempting to pick off weaker members of the small fish. They were bronze in colour with distinctive orange fins and black tails. They had large mouths that they opened and closed almost in anticipation of taking an easy meal. In an attempt to avoid them Salmo swam close to the opposite bank where there was some overhanging vegetation.
At this point the habitat was beginning to change even more, with very deep pools running into shallows. Fish seemed to everywhere but one group particularly caught his attention. They were laid close to the bottom on the gravelly shallows. They were huge, bronze in colour with the same bright orange fins, and their mouths seemed to be under their heads with strange whiskers hanging from their lips. Their size unnerved Salmo but, as he passed they completely ignored him.
Our salmon was now approaching the outskirts of Rotherham where another river joined the Don. From this point on the changes he was to encounter would be even more profound.
The new fish species that Salmo encountered were dace, chub and barbel. These three species were introduced back into the recovering river Don in 1990 being released at several locations including below Sandersons Weir. The fish were purchased by Yorkshire Water from a fish farm run by the National Rivers Authority. These were some of the first coarse fish to be artificially reared in this country and before introduction were placed in tanks where the flow was steadily increased. This developed their strength, giving them the ability to swim against the flowing river. From these introductions the populations of these species have developed and are now fully sustainable.
Dace live in large shoals preferring steadily flowing water. They feed close to the surface and are sometimes seen in large numbers taking small insects as they drift down. They rarely exceed 300g in weight or 20cm in length.
In their immature stage Chub can be easily mistaken for Dace. The easiest way to tell them apart is to look at the shape of the fins, particularly the anal fin. In dace the end of the fin is concave where as in chub the fins are convex. Chub can grow up to 4kls in weight. They have a very varied diet but can be extremely predatory feeding heavily on the fry of other species.
The iconic Barbel are extremely powerful fish and in the Don specimens of over 7kgs have been taken. They prefer conditions where there is a good flow pushing food downstream along the riverbed, such as below weirs. They can be found throughout the middle and lower reaches of the Don.