The River Great Ouse runs alongside most of the reserve and I guess the gravel pits are naturally stocked from the river, so you would expect the species found to be much the same. However, anglers have stocked some of the lakes with their preferred quarry species such as common carp and European catfish. In addition (and this needs to be confirmed) grass carp may have been introduced into some of the A1 pits to keep down the aquatic vegetation.
Most of our freshwater fish will survive in lakes, streams and rivers but a few prefer the higher oxygen levels of fast-running streams. Species like brown trout and grayling often live in the upper reaches of our rivers and migratory salmonids might pass through sluggish sections of river on their way to spawning grounds upstream, but I have never heard of trout or salmon in our stretch of the river or on the Reserve. However, we do see some species such as loaches and bullheads that have similar requirements and I guess these breed in a few of the smaller tributaries and mill streams off the main river. We see them mostly in Southoe Brook.
A lot of information on the fishes of our reach of the Great Ouse comes from the Environment Agency's surveys. In 2003 they created a fish refuge, nursery and spawning area by enlarging an old backwater near Ray House Farm. A year later it was netted and produced over 2000 small fish. These included still-water species like tench; slow-water species like bream, chub, perch, pike, eels, minnows, gudgeon, bleak and roach; and a few surprises like bullheads, stone loach, spiny loach, sticklebacks and dace. Their fishery officer, Justin Mould has added a couple of interesting extras to my list.
Anglers tell me that there are some zander (pike-perch) in our stretch of river and probably European catfish too. Barbel may be present where there are weirs.
|A baby pike is measured.|
Trout and salmon are not known to occur in our stretch of the river or any of the lakes. However Grafham water is stocked with both brown and rainbow trout and escapes are not unlikely.
Greyling (Thymallus thymallus) are not found in the Great Ouse system to my knowledge though they have been introduced in at least one mill race of the River Nene near Oundle.
Pike (Esox lucius) are found throughout the river and the lakes at Paxton Pits. Females can reach over 20 lbs here.
Roach/bream hybrids are quite common. If you see a really big roach, it is quite likely to be a hybrid.
Rudd (Scardinius erythrophthalmus) are predominantly found in still waters. They are closely related to roach, being the same shape but they tend towards yellow/gold than silver in colour and they display bright red fins and eyes. Rudd Pit has big shoals of small rudd but Cloudy Pit used to be known for producing the bigger fish. We had them in the garden pond at one time but we removed them. Almost certainly they occur in other ponds too.
Dace (Leuciscus leuciscus) are also related to roach, but they prefer clean flowing water and so are usually more common upstream. I was surprised to find them in the nets but they may venture up Southoe Brook and even enter the Heronry Lakes, but they are not a common sight.
|A fine roach, a small pike, bleak and a spined loach.|
Chub (Leuciscus cephalus) are like oversized roach, reaching over 6lbs in weight in the river. They are pretty omnivorous but can be quite predatory, despite having no teeth. They do not like still water and are unlikely to occur in our lakes.
Minnows (Phoxinus phoxinus) are river fish, but they have been found in Cloudy Pit and Washout Pit so they may be present in all the lakes.
Tench (Tinca tinca) love still waters with a lot of cover such as lily pads where they can find snails and other invertebrates on the stems and undersides of the leaves. Their presence is often made known by clouds of bubbles that are released from pondweeds as the fish nose around looking for food. They are certainly present in Cloudy, the Hayling and Rudd Pits and probably most of the others too.
Gudgeon (Gobio gobio) often hide under the little bridge on Southoe Brook near the farmyard. They are river fish but they will live in gravel pits and so I expect them to occur in the Heronry lakes which are connected to the river.
Barbel (Barbus barbus) are popular with anglers and have been introduced into a lot of eastern rivers where they did not occur naturally. They are very strong swimmers that thrive in fast flowing water (such as the River Severn and the Yorkshire Swale) where other coarse fish might not hold station. In the Great Ouse they are common upstream of Bedford and in the Ivel which is a tributary. Closer to home, they are sometimes caught in the old mill race near Buckden Marina and under the big wears at Eaton Socon and Little Paxton.
|A "mirror" carp at Paxton Pits.|
Silver Bream (Blicca bjoerkna) can be mistaken for young common bream or "skimmers", which are also silver. Justin Mould reports that the Environment Agency has caught them at Paxton Pits.
Bitterling (Rhodeus amarus) is a non-native fish from the Baltic region. They lay their eggs inside swan mussels. The only local site that I know of is in the Lode at Wicken Fen.
Common Carp (Cyprinus carpio) were introduced into the UK from Asia as a food fish, probably by the Romans but subsequently too, particularly for monastic stew ponds. They can exceed 50 lbs in weight. The biggest ones at Paxton Pits are in the Weedy Pit which is operated by a syndicate of anglers, but they are in all of the larger lakes and have even been found in our new dragonfly pond (2015). Carp are also caught in the River at Paxton Pits. They are very variable fish and some have almost no scales (leather carp) and some have just a few very large scales (mirror carp) but they are all the same species.
|A minnow caught with a maggot.|
Spined loach (Cobitis taenia) is a very rare fish in the UK, except in the Great Ouse, its tributaries and nearby lakes. It is a prominent food item for grebes at Paxton Pits and easily recognised by being extremely elongated, like a small eel. Loaches grow to only about 11 cm.
The Wels or European Catfish (Siluris glanis) belongs on the east side of the Alps in the Danube system, but it has been introduced to English rivers and lakes. Unfortunately, these huge fish been introduced into Weedy Pit and Rudd Pit as well as the river and, if they reproduce, they will have a dramatic effect on native fish stocks, wildfowl, amphibians and water voles.
Eel (Anguilla anguilla) The migration of the European eel is very well known and they have been a lucrative commercial crop in the area. The last eel catcher on the Great Ouse retired in the 1990s. There are large eels in most of the pits and in the river. We mostly see them when they are caught by otters or herons.
Perch (Perca fluviatilis) are extremely striking fish with red fins and bold bars of black and green. They are in almost every pond at Paxton Pits and the river.
Zander (Stizostedion lucioperca) look like a cross between a pike and a perch but they have strange opaque eyes that are geared to hunting in low light. Like the Wels, they were introduced into European rivers from the Danube system. The lower parts of the Great Ouse have become populated with zander and they have spread upstream beyond Huntingdon, so they are likely to be in the river at Paxton too.
Bullheads (Cottus gobio) are often called miller's thumb. (Sculpin in the USA). They live in the faster mill streams and in the upper reaches of the Great Ouse but the Environment Agency also found them in the net at the Paxton Pits fish sanctuary near Ray House Farm.
Sticklebacks (Gasterosteus avculeatus) prefer running water but they also occur in some of our lakes, including Pumphouse Pit. The Hayling ditch and Southoe Brook often hold sticklebacks when there is enough water.
Grass Carp (Ctenopharyngodon idella) have been reported from one of the A1 lakes but these reports need to be verified. This is an Asiatic fish that does not belong in our lakes. Like common carp, they can grow to be huge (up to 40 Kilos!)