Pollution and fish cause damage
In several coastal areas of the southern
and central North Sea, a decrease in the number of whelks has been observed.
The problems in these areas coincide solely with intensive human activities
that cause pollution or physical damage. In the Wadden Sea just off the
Dutch coast, whelks were common here, but are now absent. At present many
empty shells are found in this area and suggest that living specimens once
existed here. Fisherman now have to leave the coastal areas and fish the
central areas of the North Sea where ample populations still exist.
Pollution, overfishing and damage caused by fishing are the
most probable reasons for the diminishing populations. Trawling has partly
damaged the sea bottom and the collections of eggs and fishing equipment
injures the whelks. Fishing can even result in the whelks or their food
stocks being depleted.
Whelks are effected negatively by pollution. It has been shown
that whelks in coastal areas store PCB (Polychlorobiphenyls)
in their tissues, but the effects of which are unknown. The amount of pollutants
in the whelk are an inducation of how polluted the sea bottom is. In Scotland
this association is utilized to measure PCB content. The whelk is a suitable
aid for measuring how polluted the sea bottom is because it is common and
does not move over large areas.