The Marine Fauna of the Blackwater Estuary
by D.S. Davis in 1967
Studies carried out on the Blackwater Estuary in connection with the possible biological effects of the Bradwell Power Station have provided records of a wide variety of marine animals. The species identified are listed with those recorded by previous workers and evidence given for progressive natural changes in the fauna. These investigations have continued up to the present time giving the first major assessment of the fauna of the Blackwater Estuary that has yet been made.
The area covered by the investigation includes the whole of the tidal Blackwater. Most of the records come from that part of the Blackwater immediately above and below Bradwell Power Station as this is of particular interest to the present investigation.
Of the 41 fish species listed in the paper and given in the extracts below, 11 are identified as “common” or “very common”. 6 are listed as “Fairly Common” or “Often Common” and 13 could be interpreted as “commercially fished”....
Fairly common in the summer. Taken locally for food, sometimes in trawls but mainly by netting and harpooning in creeks.
Rare. A few specimens taken in the mouth of the Blackwater and offshore in November 1964.
Sometimes caught in the summer.
Very common in all parts of the Blackwater from Maldon seawards, on both clean and muddy bottoms. Present all the year round but more common in the summer.
Very common on the tidal flats of the Blackwater in sand and sandy-mud, from middle shore to just below low water mark. Extends from the low salinity areas below Maldon to the offshore sand banks. Sampling on the north shore of the Blackwater produced, in 1964, up to 416 per m3.
Small specimens frequently taken in trawl hauls during the summer, including some with distorted bodies. Some fine, large specimens have been taken in mid-water trawls while fishing for sprats in the winter.
Often common at places where there is some freshwater run-off from the land. Also found around the warm water discharge at the Barrier Wall, Bradwell.
Specimens, occasionally of large size, recorded from the Blackwater. During the winter of 1962-63 many were washed up dead on the shore.
Commonly caught in trawl hauls during the summer.
Fairly common seawards of Osea Island under fucoid weeds at the base of sea walls and sometimes among shells and stones lower on the shore.
Recorded as common in 1888.
Present all the year round in most parts of the Blackwater but particularly in creeks and in brackish water. Common and widely distributed in the summer.
Fairly common in the summer and taken as a food fish locally.
Fairly common. Specimens taken in trawl hauls from along the south shore and mid-river in the Blackwater and in the Bench Head area (1960-65).
One record from fishermen.
First appear in the Blackwater during the autumn but do not become common until the early winter. The fish come into the area to spawn and spawning has been observed in April 1963 and April 1964 on the Colne Bar and Eagle. The eggs are attached to stones and shells on the bottom. The young Herring or whitebait may be seen throughout the year. These fish are mainly a smaller variety than the North Sea Herring, but the larger fish do also occur. The best fishing takes place when the Herring are shoaling in preparation for spawning. The years 1954-56 were poor for the fishery but there has been an improvement up to 1965. The 1963 season gave the best catches for many years.
One record from fishermen.
Fairly common in trawl hauls in the Blackwater.
Occasional in summer.
Lobsters are not common but may be taken occasionally in trawl hauls, particularly in the Colne Bar area. The species was once more common in the Blackwater. Present distribution is related to the availability of suitable shelter on the bottom, e.g. wrecks. Specimens have also been obtained from Bradwell Creek and the water intake culverts of Bradwell Power Station. The severe winter of 1962-63 caused heavy mortality.
Common and sometimes abundant during the summer.
Occasionally recorded at the beginning of the century, off Brightlingsea, Tollesbury and Clacton
Often common in the summer and autumn in most parts of the Blackwater and offshore.
Common in 1960, being taken in trawl hauls from Thirslet seawards, but not commonly recorded subsequently. This is another English Channel species which is at the limit of its distribution off the Suffolk coast.
Very common on the shore, from Maldon seawards in the Blackwater and in the Colne estuary. There is a wide range of habitat and some different varieties of the species are associated with these.
Salmon have not been recorded from the tidal waters, but it has been noted that on 12th April, 1904, a salmon, which must have travelled up the Blackwater, was caught at Kelvedon. Some years previous to this event, salmon could be caught in nets in the Blackwater estuary.
Very common on the sea shore, in saltings and on the bottom of the Blackwater, breeding in spring and summer. Juveniles are abundant on the shores in the autumn, but later migrate below low water mark as they out-grow the limited cover provided by the small shells and stones. Numerous in 1960 but declined during the winters of 1961-62 and 1962-63. Generally more abundant in 1965 than in 1960 showing a rapid recovery from the effects of the winter.
Mostly common in the early summer. Sometimes abundant and at other times nearly absent. Widely distributed; from Thirslet to the Mouth of the Blackwater and offshore.
Commonly taken in dredge and trawl samples from bottoms of shell and stones. Recorded as occasional by Cole (1888) and as present between Osea Island and Bradwell.
Very common and often abundant in the winter forming the basis of an important fishery. There are marked fluctuations in the catches from year to year. 1955 and 1956 were good years but from then until 1961 were comparatively poor. There was then an improvement to the very good seasons of 1963 and 1964. The fish come into the Blackwater for spawning, which takes place in the late winter. After this the fish move out of the area.
Common in the winter but also present at other times.
One specimen caught at West Mersea in 1907. Noted as being common in the Thames Estuary in 1960.
Occasional in the summer; recent records from Cocum Hills, Thirslet (1962) and at the Barrier Wall, Bradwell (1965).
Recorded at Maldon and Heybridge in 1886, 1889 and 1898, the largest being 7 ft. 11 ins. in length. There are no recent records.
Common in the spring and summer with sometimes an extension into the autumn. Breeds in the spring and the juveniles are to be seen in the late summer. This species is a mainstay of the local inshore fishery.
Fairly common. Caught in trawls on the Bench Head and offshore (1962) and by anglers in the Blackwater. A record nine foot Tope was caught off Maylandsea in 1847.
Noted as being caught in the Blackwater Estuary in 1889. Recently re-introduced to non-tidal parts of the Blackwater by the Essex River Authority.
One record from local fisherman.
Whales have been seen or have become stranded on shores in the area from time to time.
Often common during the summer and autumn.