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Van den Broek, Willem Louis Frits (1977) Aspects of the biology of fish populations from the Medway Estuary, based on power station intake sampling with special reference to parasitism and pollution. Doctoral thesis, City of London Polytechnic.
Historical records suggest there has been a decline in the diversity of fish species in the Medway Estuary. The aims of the present study were to assess the type and composition of fish populations currently using the estuary, investigate aspects of their biology and gather information on the occurrence of specific pollutants in their tissues with a view to evaluating the influence of man's activities.
Quantitative sampling was carried out monthly between 1973 and 1975 from the intake screens of Kingsnorth Power Station. Trawl samples were also taken as a check for selectivity.
During the study over 46,000 fish, divided between 59 species, were collected. All individuals were weighed and measured, and selected species were aged. The annual cycle of species-occurrence, their relative abundance, population structure and growth of the most common species were investigated.
The diets of plaice, Pleuronectes platessa L., flounder, Platichthys flesus (L.), whiting, Merlangius merlangus (L.) and pouting, Trisopterus luscus (L.) were monitored. Seasonal and/or age variations in food intake and feeding behaviour were considered in conjunction with parasite and pollution studies.
The integumental tissues and branchial cavities of fish were inspected for parasites. Adults of the blood-feeding ectoparasitic copepod Lernaeocera branchialis (L.) infested whiting. Fish so infected showed a statistically significant reduction in body weight. Also, a brief study of their liver lipids revealed an approximately 50 percent loss in weight and this primarily reflected lower levels of phospholipid.
Selected fish, and some of their dietary constituents, were analysed for organochlorine pesticides, polychlorinated biphenyls and five heavy metals. Heavy metal levels were low in comparison with other A literature values. Chlorinated hydrocarbon values showed no marked seasonal variations connected with agricultural activities but their concentrations were correlated with the lipid content of most tissues.
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