240
THE ESSEX NATURALIST
closer to land. By the end of summer their numbers diminish,
and a little later they will journey outwards to deep sea waters,
returning the following spring.
More than 50 years ago Dr. Murie suggested that on the
approach of the winter, the pink shrimps move to somewhere off
the Norfolk and Suffolk coast. In the spring they would appear
opposite Orfordness towards the Wallet and then make shore-
wards and southwards among the various deeps and channels to
Prince's and Queen's Channels, where they would remain
abundant for several weeks. Then they would move towards the
Girdler, Oilman and Red Sand and, still later, head up the
Thames Estuary, becoming more scattered and mixing with the
brown shrimps and even reaching beyond the Nore (Fig. 3).
The wintering grounds of the pink shrimp had remained a
mystery during these years, and even at present the problem
has not been solved completely. Information from various
shrimpers tended to support the view that the pink shrimps
usually remain longer on grounds off Harwich, and also appear
sooner than further south. Early February 1955, two short
exploratory trips were made in the Wash and off the Suffolk
coast, with the Ministry's M.R.V. ONAWAY, with the aim of
obtaining information on winter migrations in these areas. No
conclusive results were obtained from the Wash, because the
number of pink shrimps trawled were too small to suggest a
wintering ground. The picture off the Suffolk coast, however,
was quite different. A good concentration of pink shrimps was
located at one station, about 11 miles east of Aldeburgh, and
at a depth of 20 fathoms. Unusual quantities of live "ross",
with colonies of up to 6 inches in height were found on this
station. A very interesting point was the discovery that the
sample contained 97.5 per cent. female shrimps carrying spawn.
Densities of pink shrimps, north and south of the station de-
creased gradually. It was evident, therefore, that one of the
wintering grounds of the populations fished from the Essex ports
was situated around this station, where food was also available.
It is possible that there are other wintering grounds further
south or eastwards from the Suffolk coast.
The pink shrimp concentrates on grounds where "ross" is
abundant. "Ross" is the honey-comb colony built from sand
particles by two small marine polychaetes (Sabellaria spinulosa
and S. alveolata). The belief of the east coast shrimpers that
"ross" is an attraction to pink shrimps is well founded. This is
the reason for using the "tell-tale". Live "ross" with a fair
number of pink shrimps, indicates a good concentration over the
ground, while dead "ross" with a very small number indicates a
small or a poor catch. This, however, should not be accepted
as a general rule, since on several occasions when live "ross" was
abundant, catches proved to be poor.
Until recently no detailed account existed of the food taken
by the pink shrimp. Murie (1903) did refer to "ross", and another