GOBIES IN THE UPPER BLACKWATER ESTUARY 121
Gobies in the Upper Blackwater Estuary—
Notes on their Identification
By R. J. C. Barron
School of Natural Sciences, The Hatfield Polytechnic, Hatfield, Herts
Summary
The field identification of six species of goby found in the Blackwater
Estuary* is discussed. Their relative abundance at Decoy Point, near
Maldon is reported, as found during fishing trips by the author. The
Common and Sand Gobies dominate the bottom fauna during the autumn
and the Black Goby is probably more common than previously reported.
Introduction
The estuarine conditions of the Blackwater above Osea Island are
suitable for several species of goby and Davis (1967) lists four species as
being present in the Blackwater Estuary as follows:
Pomatoschistus minutus (Pallas, 1770) the Sand Goby (listed as 'common'
in occurrence); Aphia minuta (Risso, 1810) the Transparent Goby ('occa-
sional'); Gobius niger Linnaeus 1758, the Black Goby ('one specimen from
the North shore in 1960') and Chaparrudo flavescens (Fabricius, 1779) the
Two-spot Goby ('last reported by Cole in 1888'). This list was not added
to by Barnes and Coughlan (1970) during a survey carried out in May
1970. The Common Goby, Pomatoschistus microps (Kr0yer, 1840), was
not included since its preference for shallow water placed it outside the
sampling areas. It is found, however, in the Blackwater Estuary (Wheeler
1969).
I have been collecting fish for laboratory work since 1973 and gobies
have always been present at the site near Decoy Point, often reaching
apparent densities of five or six fish per square metre at low-water during
the autumn. The dominant species were P. microps and P. minutus with an
occasional specimen from the other species. In this paper I will consider
the field identification of these species and their relative abundance at
Decoy Point.
Fishing Gear and Site
A beam-trawl net and a push net have been used for sampling. Both of
these nets were made from shrimp netting (18 mm mesh) with a cod-end
of lant-netting (9 mm mesh). The push net was 90 cm wide at the mouth,
the beam-trawl 110 cm; both nets were approximately 1.5 m long. Since
both nets were worked from the beach without the aid of a boat, the