56 THE ESSEX NATURALIST
Order Hypotremata
Rajidae
Raja clavata (Linne) Thornback Ray
Common in the spring and summer with sometimes an exten-
sion 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.
Some specimens carry the parasitic leech Pontobdella muricata.
Trygonidae
Dasyatis pastinaca (Linne) Sting Bay
Occasional in the summer; recent records from Cocum Hills,
Thirslet (1962) and at the Barrier Wall, Bradwell (1965).
Class PISCES
Order Chondrostei
Acipenseridae
Acipenser sturio (Linne) Sturgeon
Recorded at Maldon and Heybridge in 1886, 1889 and 1898,
the largest being 7 ft. 11 ins. in length. A large specimen was
caught in the Colne in 1700 (Essex Naturalist). There are no
recent records.
Order Isospondyli
Clupeidae
Clupea harengus Linne 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 white-
bait 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.
Clupea sprattus (Linne) 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.