A.D.
Vethaak, Institute for Coastal and Marine Management/RIKZ, PO Box 8039,
4330 EA Middelburg, The NetherlandsA.D.
Vethaak, Institute for Coastal and Marine Management/RIKZ, PO Box 8039,
4330 EA Middelburg, The Netherlands
Studies on the prevalence of diseases/disorders of wild marine fish are an
important component of national monitoring programmes aiming at an assessment
of the quality of the marine environment. Special attention is given to two
fish species, the flounder (Platichthys flesus) and the dab (Limanda limanda).
Major pathological conditions that have been associated with environmental quality
include: (1) lymphocystis, a viral disease; (2) skin ulceration, a bacterium-associated
condition; (3) epidermal hyperplasia/papilloma, unknown aetiology; (4) liver
neoplasia, caused by environmental carcinogens, e.g. PAHs; and (5) intersex
gonads in male fish most likely caused by estrogenic contamination.
The
purpose of this paper is to present information on temporal trends of the above
pathological conditions in dab and flounder in Dutch coastal waters and on a
wider regional scale in the North Sea. Long-term disease data (1981-1999) from
the International Council for Exploration of the Sea (ICES) Environmental Data
Centre, and data from specific studies on skin ulcerations and liver neoplasia
in flounder in Dutch coastal waters will be discussed.
It is concluded that pathological conditions in flatfish, that showed high prevalences
in the 1980s, show reducing prevalences in the 1990s at most sites, which suggest
that general water quality is improved. An exception is the occurrence of intersex
gonads and other estrogenic effects, for which time series information is not
yet available.
During the last few decades increasing attention has focussed on the occurrence
of fish diseases in the North Sea. Field, laboratory and mesocosm approaches
have been succesfully applied for understanding contaminant effects on fish
health.The problem of the possible influence of environmental factors on disease
is very complex.
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