fish in the river darent
A large Chub
People belong to DRiPS for many different reasons, but many members are likely to have an interest in the fish population of the river. There are both 'game' fish populations (such as brown and rainbow trout) and ‘coarse’ fish (such as chub, dace, roach, perch, pike, minnow and so on.) Probably, most of the ‘game’ fish come from artificial stocking: some years ago, at Shoreham, a large number of small brown trout were introduced, and anglers there caught many of them.
A good way to find out what is in the river is to walk along, quietly, with polaroid sunglasses, and after a while your eyes will become acclimatised and you will be able to see what is there. Large blunt-headed fish with dark tails will be chub, and fish which ‘flash’ silver sides in the river will be dace. In quiet spots, you may see the elongated form of the pike, and fish with dark stripes are perch. Some years ago, again at Shoreham, there was a single bream, of about 2 pounds weight, living happily in the deeper water. Very small fish in large shoals are likely to be minnows, a food source for chub (on left) , perch, pike, and trout (pictured below) which often feed on them.
A good way to find out what is in the river is to walk along, quietly, with polaroid sunglasses, and after a while your eyes will become acclimatised and you will be able to see what is there. Large blunt-headed fish with dark tails will be chub, and fish which ‘flash’ silver sides in the river will be dace. In quiet spots, you may see the elongated form of the pike, and fish with dark stripes are perch. Some years ago, again at Shoreham, there was a single bream, of about 2 pounds weight, living happily in the deeper water. Very small fish in large shoals are likely to be minnows, a food source for chub (on left) , perch, pike, and trout (pictured below) which often feed on them.
Brown Trout
Another way of finding out what is in the river is to take off your shoes (or put wellies on) and go for a paddle, upstream. If you gentry overturn large stones you may spot a stone loach or bullhead amongst the shrimps and snails. If you turn any stones over, replace them the way you found them very gently. Sadly, you are unlikely to find the native crayfish which I used to: they’ve been pretty much wiped out by disease introduced by foreign species (signal crayfish).
Every so often, the Environment Agency do fish surveys on the river, and we reproduce here their 2011 summary of what they found. They try to be consistent in their techniques. So, they use electric fishing equipment to stun (not kill) the fish, which they then net out to assess and then return alive and well. They look into what species there are in each area of river, the number of fish (density) per 100m2, the weight (biomass) of each species in each area, their growth rates, and whether or not there is a good spread of different ages of fish and are they successfully breeding.
Perch
In 2011, fish surveys were undertaken at fourteen sites in the Darent catchment from 23 May to 5 October 2011 using standard electric fishing techniques. A total of 2076 individuals of 13 species were captured during the surveys, in addition to bullhead, minnow, stone loach and three spined stickleback. Roach was the most abundant species, accounting for 41% of the total catch, followed by dace & chub at 20% and 19 % respectively and perch at 5%.
Perch was the most widespread species, occurring at eleven out of the fourteen survey sites followed by chub and roach which each occurred at nine of the fourteen survey sites. The bullhead, which is of conservation significance, occurred at eight of the fourteen survey sites while the declining eel occurred at half of the survey sites, albeit at generally low densities. Brown trout occurred at six of the fourteen survey sites although some of these brown trout were stocked fish (notably at Preston Farm and Twitton Brook where stocked rainbow trout also occurred).
Perch was the most widespread species, occurring at eleven out of the fourteen survey sites followed by chub and roach which each occurred at nine of the fourteen survey sites. The bullhead, which is of conservation significance, occurred at eight of the fourteen survey sites while the declining eel occurred at half of the survey sites, albeit at generally low densities. Brown trout occurred at six of the fourteen survey sites although some of these brown trout were stocked fish (notably at Preston Farm and Twitton Brook where stocked rainbow trout also occurred).
A pike
Densities ranged from 1.5 to 79.6 fish/100m2. The highest densities were recorded at Bexley Park on the River Shuttle where a total of 196 fish were captured, dominated by roach (n = 157). The lowest densities were found at Quebec House Car Park, Westerham, where a total of 3 fish were caught (excluding minor species).
Standing crop or biomass averaged 2306g/100m2 along the Darent and was dominated by chub (27%), brown trout (24%) and roach (14%). Lullingstone produced the highest overall biomass (4573g/100m2) whilst the lowest was recorded at Quebec House Car Park, Westerham (26.5g/100m2).
Dace and roach in the River Cray had average growth rates when compared to the species standards for dace and roach in southern English waters having Percentage Standard Growth (PSG) values of 102% and 91%. Dace were aged up to 5+ and roach up to 7+. There was good recruitment of chub, dace, perch and roach in the River Cray. Chub in the River Darent had an average growth rate when compared to the species standards for chub in southern English waters, having a PSG value of 93%. Dace and roach had slow growth rates when compared to the species standards for dace and roach in southern English waters, both having PSG values of 82% respectively. Chub were aged up to 16+, dace to 6+ and roach to 7+. Pike were aged up to 7+ and brown trout up to 5+.
There was good recruitment of chub, dace, gudgeon, perch, pike and the abundant roach in the River Darent. There was good recruitment of brown trout too though care needs to be taken in interpretation due to the presence of large, stocked trout.
Analysis of fish species diversity across Darent catchment sites indicates that:
Park Farm and Sundridge were characterised by a brown trout dominated community with a single dominant minor species (bullhead or stone loach depending on the available habitat).
Twitton Brook and Preston Farm showed the least similarity to the general picture, probably due to the stocking of considerable quantities of trout.
Sevenoaks, Lullingstone and Horton Kirby showed similar fish communities where roach is dominant but there is one important sub-dominant cyprind (chub or dace) with good numbers of bullhead and minnow present.
Hawley, Dartford and Maiden Lane were similar, characterised by dominant roach with a sub-dominant perch community.
It is worth noting that the site with easily the most diverse fish population (Shannon Index = 2.015) was at Lullingstone. The site is immediately downstream of a major obstruction at a lake outlet and has also benefited from Environment Agency habitat enhancement work in recent years.
By contrast Dartford Park and, in particular, Maiden Lane, have channelised homogeneous habitat dominated by a single generalist species (roach) and have the lowest diversity scores (0.6 and 0.4).
Stephen Crowley, March 2014
Standing crop or biomass averaged 2306g/100m2 along the Darent and was dominated by chub (27%), brown trout (24%) and roach (14%). Lullingstone produced the highest overall biomass (4573g/100m2) whilst the lowest was recorded at Quebec House Car Park, Westerham (26.5g/100m2).
Dace and roach in the River Cray had average growth rates when compared to the species standards for dace and roach in southern English waters having Percentage Standard Growth (PSG) values of 102% and 91%. Dace were aged up to 5+ and roach up to 7+. There was good recruitment of chub, dace, perch and roach in the River Cray. Chub in the River Darent had an average growth rate when compared to the species standards for chub in southern English waters, having a PSG value of 93%. Dace and roach had slow growth rates when compared to the species standards for dace and roach in southern English waters, both having PSG values of 82% respectively. Chub were aged up to 16+, dace to 6+ and roach to 7+. Pike were aged up to 7+ and brown trout up to 5+.
There was good recruitment of chub, dace, gudgeon, perch, pike and the abundant roach in the River Darent. There was good recruitment of brown trout too though care needs to be taken in interpretation due to the presence of large, stocked trout.
Analysis of fish species diversity across Darent catchment sites indicates that:
Park Farm and Sundridge were characterised by a brown trout dominated community with a single dominant minor species (bullhead or stone loach depending on the available habitat).
Twitton Brook and Preston Farm showed the least similarity to the general picture, probably due to the stocking of considerable quantities of trout.
Sevenoaks, Lullingstone and Horton Kirby showed similar fish communities where roach is dominant but there is one important sub-dominant cyprind (chub or dace) with good numbers of bullhead and minnow present.
Hawley, Dartford and Maiden Lane were similar, characterised by dominant roach with a sub-dominant perch community.
It is worth noting that the site with easily the most diverse fish population (Shannon Index = 2.015) was at Lullingstone. The site is immediately downstream of a major obstruction at a lake outlet and has also benefited from Environment Agency habitat enhancement work in recent years.
By contrast Dartford Park and, in particular, Maiden Lane, have channelised homogeneous habitat dominated by a single generalist species (roach) and have the lowest diversity scores (0.6 and 0.4).
Stephen Crowley, March 2014
