An extensive trial to examine physiological and biochemical changes in perch (Perca fluviatilis) inhabiting coastal waters polluted by bleached kraft mill effluents (BKME) has been carried out. The investigations were performed at four different times of year. Fish from a reference site and from sampling sites 2, 4.5, 8, and 10 km from the discharge point were examined. The results of the investigation show profound effects of BKME on several fundamental biochemical and physiological functions. Typical symptoms in perch from the polluted areas were reduced gonad growth, enlarged liver, and very strong induction of certain cytochrome P-450-dependent enzyme activities in the liver. Elevated levels of ascorbic acid in liver tissue and abnormal carbohydrate metabolism reflect the effluent's ability to cause metabolic disorders. Marked effects on the white blood cell pattern indicate a suppressed immune defence. Alterations in the red blood cell status and in the ion balance suggest that the demand for oxygen by certain tissues was increased and that gill function was impaired, respectively. The toxic effects were most pronounced in fish living up to 4.5 km from the discharge point, but some disturbances (e.g. cytochrome P-450 induction, reduced gonad size, and hematological alterations) were observed in fish caught as far as 8–10 km from the kraft bleach plant.

Physiological methods, previously used as health indicators in laboratory investigations on fish exposed to environmental pollutants, have been applied to feral fish inhabiting coastal waters polluted by bleached kraft mill effluents (BKME). The results show that BKME affect important physiological functions and thereby the state of health of the fish in the receiving body of water. Typical symptoms were reduced gonad growth, enlarged liver, strong induction of enzymes in the hepatic mixed function oxidase system, elevated content of ascorbic acid in liver tissue, altered carbohydrate metabolism, disturbed ion balance and marked effects on the red and white blood cell pattern. Good agreement was found between the toxic effects detected in fish exposed to BKME in nature and those observed in laboratory investigations. The toxic effects were most pronounced in fish living up to 4.5 km from the discharge source, but some disturbances could be observed even in fish caught 8-10 km from the kraft pulp plant. This indicates that the area of influence where the BKME exert biological effects is much larger than was previously considered.

Ranges in the means of blood measurements from 121 Baltic salmon taken on nine occasions spread over an annual cycle were: packed cell volume or haematocrit; blood haemoglobin; red blood cell counts including immature erythrocytes; mean corpuscular haemoglobin concentration; mean cellular haemoglobin content and mean cellular volume. Seasonal changes appeared in all blood variables. Ontogenetic differences occurred in RBC and mean cellular volume when comparing 1 + parr with 2 + smolts in August one year apart, and in haemoglobin, RBC and immature RBC when comparing I + parr with adults once in November 1976. This points to greater influence upon haematological variation by season than by age. Significant regressions found within age groups, between pairs of mutually independent blood variables, are presented. 565 0022-1 112/84/050565+ 15 $03.00/0 0 The Fisheries Society of the British Isles HAEMATOLOGICAL DETERMINATIONS Packed cell volume, PCK or haematocritT o avoid the swelling of red blood cells which can occur in fish blood stored anaerobically, PCV was determined completely within 15 mm after sampling (Soivio et al., 1974).

Haematological variations were studied in a European eel population, Anguilla anguilla L., naturally infested by the sanguivorous nematode Anguillicola erassus. This occurred off the Swedish Baltic coast in an area reeeiving heated coohng water from a nuclear power station. The erythrocyte count, haematoerit, leucocrit, haemoglobin eoncentration, mean eorpuscular volume, mean coTpuscular haemoglobin and mean corpuscular haemoglobin eoncentrations, the various eell types in peripheral blood, serum iron concentration, the amount of total serum protein, and serum protein fractions a,, fix. fV2, ft and y were all measured. Each variable was correlated to: (1) the intensity of infestation, i.e. number of parasites per host; and (2) a parasitization index, i,e, the weight of parasites per somatic weight of the host. Most variables showed no or only minor reactions to the infestation. However, a marked increase in the y-fraction of serum proteins, reduced lymphocyte numbers and increased granulocyte numbers are indieativc of a humoral and cellular immune response.

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