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”....
Bass
Fairly common in the summer. Taken locally for food, sometimes in trawls but mainly by netting
and harpooning in creeks.
Blue Whiting
Rare. A few specimens taken in the mouth of the Blackwater
and offshore in November 1964.
Brill
Sometimes
caught in the summer.
Brown Shrimp
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.
Cockle
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.
Cod
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.
Common Eel
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.
Conger Eel
Specimens,
occasionally of large size, recorded from the Blackwater.
During the winter of 1962-63 many were washed up dead on the shore.
Dab
Commonly caught in
trawl hauls during the summer.
Flat Winkle
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.
Five-bearded Rockling
Recorded
as common in 1888.
Flounder
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.
Garfish
Fairly common in the summer
and taken as a food fish locally.
Great Pipe-fish
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).
Hake
One
record from fishermen.
Herring
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.
John Dory
One
record from fishermen.
Nilsson
Fairly common in trawl hauls
in the Blackwater.
Lemon Sole
Occasional
in summer.
Lobster
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.
Plaice
Common and sometimes
abundant during the summer.
Porbeagle Shark
Occasionally
recorded at the beginning of the century, off Brightlingsea,
Tollesbury and Clacton
Pout
Often common in the summer and autumn in most parts
of the Blackwater and offshore.
Prawn
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.
Rough Winkle
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
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.
Shore Crab
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.
Sole
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.
Spider Crab
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.
Sprat
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.
Smelt
Common in the winter but also
present at other times.
Skipper
One
specimen caught at West Mersea in 1907. Noted as being common in the Thames Estuary in 1960.
Sting Ray
Occasional
in the summer; recent records from Cocum Hills, Thirslet (1962) and at the Barrier Wall, Bradwell (1965).
Sturgeon
Recorded
at Maldon and Heybridge in 1886, 1889 and 1898, the
largest being 7 ft. 11 ins. in length. There are no recent records.
Thornback Ray
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.
Tope
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.
Trout
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.
Turbot
One
record from local fisherman.
Whales
Whales
have been seen or have become stranded on shores in the area from time to time.
Whiting
Often common during the summer and
autumn.
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