The Otter Lutra lutra in Essex 1996-2002
Hamford Water
Two pairs of Otters were introduced into Hamford Water in 1996. During the survey of 1996 all four
monitoring sites were found positive with spraints recorded on the borrowdykes behind the sea wall.
One site on the Holland Brook where it discharges into the sea 5 km south of Hamford Water was
also positive. In 1997 three of the sites produced signs but an Otter was killed on the B1414 at
Beaumont-cum-Moze on 18/19 December 1997. In 1998 a survey was made of Horsey Island, a
privately owned island in Hamford Water where the 1996 introduction of Otters was made. It offers
ample fresh water but no signs were found. Only one of the standard survey sites on Hamford was
marked in 1998. However many spraints were discovered along the freshwater borrow dykes by the
municipal waste disposal facility at Dovercourt beach (adjacent to Hamford Water), a site heavily
used by anglers and dog walkers. Since then no signs have been located on or near Hamford Water,
although there was an unconfirmed observation in 1999.
River Colne catchment
In 1995, before the start of the current project, sites along the River Colne were surveyed for Otters
but nothing was found. In 1996, 16 of 37 sites (43%) proved positive with distribution extending
from Great Yeldham near to the top of the river to Rowhedge which is on the estuary downstream of
Colchester. One tidal site on the Roman River near its confluence with the Colne was also marked as
was the Bourne Brook, a small tributary that flows into the middle reaches of the Colne. The change
from 1995 to 1996 was therefore striking. In December 1996 an Otter was killed by traffic at White
Colne.
In 1997,46% of sites were occupied and while no evidence was found in the tidal stretches, animals
were still present from the upper river, including the Gosfield Lakes where disturbance from fishing
and water sports is significant, to Colchester. The lakes were still occupied in 1998 but overall,
throughout the catchment, only four of the 37 survey sites were positive and it seemed that the Colne
population, having appeared with such apparent suddenness had suffered a severe and equally sud-
den decline. Several sites were rc-chcckcd but the result did not improve.
in 1999 and in 2000 nothing was found and in 2001, when only 13 sites could be monitored due to
foot and mouth, the result was again negative. In 2002 the Colne was re-surveyed in March and still
no animals could be located but in April spraints were found along a stretch of approximately 9 km
upstream from Colchester. An Otter was back on the Colne after an apparent absence of three years.
It may have moved from the Stour as some tributaries of the two rivers rise in close proximity,
requiring only a few kilometres of overland travel.
From a peak in 1997 the index value (Fig. 10) collapsed to zero in 1999.
River Blackwater catchment
This system consists of the Blackwater, known in the headwaters as the Pant, together with its
tributary, the River Brain. In 1996, 33 sites were monitored and no Otter signs were found but, in
1997,13 sites were positive along the middle and lower reaches of the river. However, in 1998 only
seven sites produced signs and these were all on the lower river. In the following year the number of
sites where Otters were recorded was ten, rising to 15 in 2000 with signs found for the first time on
the River Brain showing that animals were passing through the town of Witham. In 2001 only five
sites proved positive but then only 21 sites could be visited due to foot and mouth disease. In 2002
nine sites were positive but distribution remained restricted to the lower reaches (downstream of
168
Essex Naturalist (New Series) 20 (2003)