The Lost Fish Species of the Lower River Don

Our Trustee Chris Firth (MBE) describes the historical drainage of the lower Don’s diverse wetlands, which species can still be found and which are yet to return.

Prior to the early part of the 17th century the lower River Don consisted of a vast area of wetland which extended from the town we now know as Thorne all the way to the confluence of the Rivers Trent and Ouse. It then extended up the Trent valley as far as Misterton and across from there to the outskirts of Doncaster. It covered an area equivalent to 90 thousand acres and encompassed one of England’s foremost Royal hunting estates, the Hatfield Chase.

This area of land known as the Isle of Axholme was made up of a myriad of wetland habitats including lakes, meres, ponds, marshes, reed beds and river channels including those of the Rivers Idle and Torne which at that time were tributaries of the Don. Most notable of the features was Bradmere, a huge lake which at the time was regarded as the second largest body of fresh water in Yorkshire eclipsed only by Semerwater up in the Yorkshire Dales. Bradmere stood immediately to the west of Thorne and received the flow of the Don as it coursed its way into the wetlands of the Isle of Axholme. This area was subjected to frequent inundation from both spring tides and fluvial flooding and provided conditions which accommodated a huge variety of fish species. Passing annually up the river channel were huge numbers of salmon and sea trout heading for the clean fresh conditions of the upper Don and its tributaries. An indication of the numbers of these species frequenting the river can be gained from their market value at the time. Salmon was the cheapest fish available and was generally eaten by only the poorest in society. In comparison, eels were jealously guarded with the rights to fish for them most often held by Monastic Orders. In the lakes, ponds and meres species such as roach, bream, perch and pike would have abounded and these would have been the most common species exploited by the residents as a source of food. But there were other species which despite the Don’s recovery from gross pollution, are no longer found. Species such as the smelt a small silvery fish which appeared in huge shoals and moved up the tidal areas to spawn. Another was the burbot a freshwater member of the cod family. Both of these species would have been present in huge numbers as would river lamprey which would have entered the river to reproduce. Interestingly the river lamprey’s larger cousin the sea lamprey made its first appearance in the Don in 2016 after more than a century of absence. All of these species were tolerant of the brackish conditions created by saline influence of the Humber Estuary.

Today, smelt are still found in parts of the Humber Estuary but in very small numbers compared to the vast shoals which once existed. They make their way into the estuary between January and April to breed then drop back out to sea. As late as the 1970s large numbers of this species would make their way, by way of connected channels, into the lakes created by redundant mineral workings along the Humber banks around Barton and Hessle and annually their presence could be detected by a distinctive smell of thyme rising from the water. Their decline has been blamed on a number of factors mainly associated with land drainage activities. The introduction of clough gates and pumping stations at the outfalls into the estuary undoubtably had a significant impact as it restricted access to many of the most suitable spawning sites. Despite there being a remnant population in the estuary, no sign of them returning to the River Don has been found.

The burbot is the only member of the cod family to live in freshwater and as earlier stated, was once common in the rivers connected to the Humber. Its eating qualities were regarded as very good despite its ugly appearance and it would undoubtably have been a prized dish for the residents of the lower Don. Burbot were still present in relatively large numbers in the Yorkshire Derwent in the late 1940’s and early 50’s and my uncle was a regular visitor to Bubwith and Wressle often returning with half a dozen fish for the table. Its decline and later extinction has been blamed once again on land drainage practices, particularly the construction of the barrage which was built at the outfall of the Derwent into the River Ouse, changing the tidal nature of the river. Today the burbot is recognised as extinct in British waters.

sturgeon no copyright
The European Sea Sturgeon, Acipenser sturio

Probably the most iconic species yet to make a reappearance is the European sea sturgeon, once an occasional visitor to the Don. These huge fish, some weighing in excess of 200 lbs, probably entered the river in search of suitable spawning sites but the construction of weirs, particularly the one at Doncaster built around the 12th century, would have been a complete barrier to their upstream movement. There are records of these fish being speared and gaffed when they appeared in the weir pool at Doncaster where, because of their size, they would have been easy prey to the local human population.

The recovery of the River Don’s fish population has been remarkable over the last 25 years with 27 of the river’s original 32 recorded species now present within the system. The prospects for the return of smelt and river lamprey are probably good despite the national decline of these species but the likelihood of us witnessing the return of burbot and sturgeon are poor, particularly with burbot which is recognised as extinct in British waters. The only possibility of this happening would be reintroduction from populations existing in Europe, something which has been considered. We must recognise however that because of the extensive draining of the Don’s tidal floodplain in the 17th century, the habitat of the lower river has fundamentally changed resulting in little being left of the habitat that supported such a remarkable fishery.

We should never say never and perhaps some time in the future the work that has taken place to restore this once incredible river system will be rewarded with the return of all of its historic fishery inhabitants.