a tumor of the skin, while in other areas of the German Bight and the North Sea the
percentage of this disease in dab was about 0.5% (Dethlefsen and Watermann 1980).
Unfortunately, up to the day in June 1981, while I am finally correcting this book,
basic data in this interesting correlation have not been published, and experts are discussing matters with different points of view. It could well be that a closer look into
the basic material allows explanations other than the supposed correlation with
dumping, for example with the effluents of the polluted Elbe river (Gerlach 1981).
In principle, however, it could well be that dab with its very delicate skin is a more
sensitive indicator than invertebrate macrobenthos living in the sediment. Future
scientific investigations hopefully will make the case clear. The public discussion of
the possible correlation between dumping of wastes in the North Sea and fish disease,
including activities of the Greenpeace organization, has forced the German and Dutch
Governments to some activity; probably the licence for dumping will expire soon,
in the Netherlands in March 1982.
Disease is a concomitant of life for any species of organism; symptoms of a disease as
such can be quite normal under undisturbed, natural conditions. However, any departure from normal environmental conditions, natural accidents, or man-made impact
produces a degree of stress and may contribute to an increase of diseases. It is welldocumented that human activity has increased stress for fish in estuarine and nearshore waters because concentrations of toxic heavy metals (see Chap. 3.1) or toxic
organics (see Chap. 3.2) have increased, or because the oxygen regime is burdened
with degradable organic substances (see Chap. 4.3). Examples of good correlations
between the frequency of fin rot and ulcer in fishes and shell disease in crustacea, and
with pollution have been given (Sindermann 1978). However, there are many diseases
where up to now such correlations could not be demonstrated beyond doubt.
Back to the period of 1900 there are reports about the "cauliflower disease" of eel
(AnguilliI anguilliI) in the lower reach of the Elbe River. But such tumors in the head
region of eel seem to occur nowadays more frequently, in 12-28% of all eel caught
in summer, but only in Central Europe, not in West Europe and the Mediterranean
region. It is not known what causes the skin defects; stress from reduced oxygen
concentrations seems to trigger its outbreak (Peters 1981). On the Pacific coasts of
Canada and the northern U.S.A. flatfish tumors are more frequent close to larger
cities and close to sewage inlets. But again there is no direct proof that pollution
causes these diseases. Apparently geographical areas exist in which flatfish or eels
have a certain chance of developing skin tumors, and pollution stress may increase the
chance. But outside those areas populations of such fish are not affected by tumors
even if they inhabit polluted estuaries (Stich et al. 1977).
To make any firm association of the disease with environmental pollution requires
knowledge of the history of the disease and the pollution situation, a following-up of
future trends, knowledge of the life history of the disease, a baseline study to compare
polluted with unpolluted situations, and, if possible, experimental reproduction of the
disease by exposure to contaminants (Sindermann 1978). In the case of the epidermal
papillomes of dab in the region ofHelgoland Bight where wastes of the titanium pigment
industry are dumped, up to now only the first attempts have been made to make a case
out of a baseline study. Surprises may occur with future research. At this moment one
should not misinterpret the evidence from the invertebrate bottomfauna (Fig. 38).
60
percentage of this disease in dab was about 0.5% (Dethlefsen and Watermann 1980).
Unfortunately, up to the day in June 1981, while I am finally correcting this book,
basic data in this interesting correlation have not been published, and experts are discussing matters with different points of view. It could well be that a closer look into
the basic material allows explanations other than the supposed correlation with
dumping, for example with the effluents of the polluted Elbe river (Gerlach 1981).
In principle, however, it could well be that dab with its very delicate skin is a more
sensitive indicator than invertebrate macrobenthos living in the sediment. Future
scientific investigations hopefully will make the case clear. The public discussion of
the possible correlation between dumping of wastes in the North Sea and fish disease,
including activities of the Greenpeace organization, has forced the German and Dutch
Governments to some activity; probably the licence for dumping will expire soon,
in the Netherlands in March 1982.
Disease is a concomitant of life for any species of organism; symptoms of a disease as
such can be quite normal under undisturbed, natural conditions. However, any departure from normal environmental conditions, natural accidents, or man-made impact
produces a degree of stress and may contribute to an increase of diseases. It is welldocumented that human activity has increased stress for fish in estuarine and nearshore waters because concentrations of toxic heavy metals (see Chap. 3.1) or toxic
organics (see Chap. 3.2) have increased, or because the oxygen regime is burdened
with degradable organic substances (see Chap. 4.3). Examples of good correlations
between the frequency of fin rot and ulcer in fishes and shell disease in crustacea, and
with pollution have been given (Sindermann 1978). However, there are many diseases
where up to now such correlations could not be demonstrated beyond doubt.
Back to the period of 1900 there are reports about the "cauliflower disease" of eel
(AnguilliI anguilliI) in the lower reach of the Elbe River. But such tumors in the head
region of eel seem to occur nowadays more frequently, in 12-28% of all eel caught
in summer, but only in Central Europe, not in West Europe and the Mediterranean
region. It is not known what causes the skin defects; stress from reduced oxygen
concentrations seems to trigger its outbreak (Peters 1981). On the Pacific coasts of
Canada and the northern U.S.A. flatfish tumors are more frequent close to larger
cities and close to sewage inlets. But again there is no direct proof that pollution
causes these diseases. Apparently geographical areas exist in which flatfish or eels
have a certain chance of developing skin tumors, and pollution stress may increase the
chance. But outside those areas populations of such fish are not affected by tumors
even if they inhabit polluted estuaries (Stich et al. 1977).
To make any firm association of the disease with environmental pollution requires
knowledge of the history of the disease and the pollution situation, a following-up of
future trends, knowledge of the life history of the disease, a baseline study to compare
polluted with unpolluted situations, and, if possible, experimental reproduction of the
disease by exposure to contaminants (Sindermann 1978). In the case of the epidermal
papillomes of dab in the region ofHelgoland Bight where wastes of the titanium pigment
industry are dumped, up to now only the first attempts have been made to make a case
out of a baseline study. Surprises may occur with future research. At this moment one
should not misinterpret the evidence from the invertebrate bottomfauna (Fig. 38).
60