| Summary: | Cottus haemusi (Marinov
and Dikov, 1986. Acta Zool. Bulg. 3, 18–23) is an endemic fish species
that is restricted to the upper tributaries of the river Vit, Northwest
Bulgaria. After its discovery in 1986, no further investigation of
the C. haemusi population has been conducted. The
aims of the present study were to determine its current population
status based on the distribution, abundance and size structure of
the C. haemusi population and to analyse the main
environmental parameters of its habitat. Five upland tributaries
and the main river were examined in low-water periods in 2009 and
2010. Two-pass electrofishing surveys were performed at 14 sites
to estimate species presence, abundance and size distribution. C.
haemusi was only detected in two tributaries of the river
Vit: Kostina and Toplja. The current investigation failed to find
the species at previously recorded sites. The total distribution
area of this species is estimated to be 16 200 m2. The observed
abundance of the Vit sculpin ranged from 5.6 to 8.4 individuals·100
m–2, with a mean of 7.0 individuals·100 m–2.
Investigation of the size structure revealed the relatively low
contribution of one-summer-old individuals. Microhabitat preferences
did not differ significantly from other European cottidae species.
Only a higher percentage of cobbles distinguished sites with sculpins
from those without. The restricted distribution and loss of the
bullhead population from some localities in the river Vit could be
explained by human disturbance and the deterioration of natural
habitat. Several protection measures are discussed.
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