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Four homozygous (HomIso) and eight heterozygous isogenic (HetIso) strains of common carp were used in two separate experiments to examine the genetic background of a stress-related cortisol response due to a rapid temperature decrease. The homozygous sires (two high and two low) and dams (high and low) used to obtain the strains were selected based on their estimated breeding value for this trait at an age of 15 months (EBV15). In both experiments, the strains were subjected to a 9 °C cold shock at an age of 5 months. The ranking in plasma cortisol levels of the HomIso strains was identical to the ranking in EBV15 of the sires and the maximal difference of 350 nmol l−1 was similar to the expected difference based on these EBV15's. Differences between the HetIso strains were smaller than expected, and influence of non-additive genetic effects could not be detected (PDS=0.14). Estimated breeding values based on the performance of the androgenetic progeny (EBV5) in experiment 1 and general combining abilities (GCA) of the sires and dams calculated in experiment 2 were positively correlated with the EBV15 (r not significantly different from 1), providing no evidence that the stress response at 5 and 15 months are different traits. Based on the results of these experiments, it can be argued that the best method to change the stress responsiveness of common carp would be through selective breeding (exploiting additive genetic effects) rather than through crossbreeding (exploiting non-additive genetic effects).

The tissue depletion of the anthelmintic fenbendazole (FBZ) was studied in rainbow trout (Oncorhynchus mykiss). FBZ was administered orally at a dose of 6 mg kg−1 body weight. A bath treatment at a dose of 1.5 mg l−1 for 12 h at a water temperature of 12 °C was also carried out. Muscle tissue and skin samples were collected at 12 and 24 h intervals following drug administration and analysed for FBZ and the metabolites oxfendazole (FBZ-SO) and oxfendazole sulphone (FBZ-SO2) by high-performance liquid chromatography (HPLC). Following oral treatment, FBZ was detected in muscle tissue until 96 h after treatment. The highest median concentration was found at the 24 h sampling time (40 μg kg−1), thereafter a decline occurred. The levels of FBZ in the skin were higher than those found in the muscle tissue, with the highest content found at the 24 h sampling time (median 249 μg kg−1). FBZ-SO could not be detected in muscle tissue. In skin, FBZ-SO was detected in four samples out of five at the 24 and 48 h sampling points. FBZ-SO2 was not detected in all samples examined. Following bath treatment, FBZ was found in muscle tissue and skin at the 12 and 24 h sampling points only, the median concentrations being 96 and 17 μg kg−1 for muscle tissue and 282 and 109 μg kg−1 for skin, respectively. FBZ-SO was present in muscle tissue at the 12 and 24 h sampling points only. In the skin, this compound was detected until 96 h after treatment. FBZ-SO2 was not detected in all samples examined. This study clearly demonstrates that, in trout, FBZ is metabolised to FBZ-SO and that both FBZ and FBZ-SO accumulate in trout skin after administration of the drug. Furthermore, the data obtained indicate that FBZ-residues in rainbow trout following oral and bath treatments are largely depleted within 96 and 24 h, respectively.

On two shrimp farms in East Java, Indonesia, a total of 16 tambaks stocked with Penaeus monodon (Fabricius) were monitored for water quality during one growing season. The water quality parameter values were compared with production characteristics. Ranges of parameter values remained between acceptable reference values. Influences of farm, tambak and time on water quality were significant. Tambak production was explained for 25% by water transparency. Observed water quality parameter values could not be a reason for recently described decreased production. Therefore, other factors should be investigated.

Thirty-three androgenetic progeny groups of common carp were analysed using 11 microsatellite markers to (i) verify the homozygous status of the 566 androgenetic individuals, (ii) analyse the microsatellite allele segregation, and (iii) study the possible association of microsatellite alleles with phenotypic traits. In total, 92% of the androgenetic individuals proved to be homozygous at all 11 loci. Forty-three of the 47 heterozygous individuals were heterozygous at a single locus only. This heterozygosity was probably due to DNA fragments caused by UV irradiation of the eggs, although the maternal origin of the fragments could not be proved beyond doubt. Screening with 11 microsatellites also revealed two linkage groups, a segregation distortion at two microsatellite loci, and the possible association of some microsatellites with mass, length, stress-related plasma cortisol levels, and basal plasma glucose levels. The success of the linkage and association study could be explained by a low recombination frequency due to high chiasma interference. This would imply a relatively short genetic map for common carp.Key words: doubled haploids, residual heterozygosity, microsatellite allele segregation, linkage analysis, common carp.

The influence of flumequine on mitogen induced lymphoid cell proliferation in European eels ( Anguilla anguilla L., 1758) was studied. For this purpose an in vivo test, using peroral drug administration followed by successive intraperitoneal injections with concanavalin A (ConA) or bacterial lipopolysaccharides (LPS) and 5-bromo-2′-deoxyuridine, was applied. Direct counting of proliferated cells in blood smears revealed that flumequine possesses mitogenic properties. A synergistic and an antagonistic effect of the drug was observed after LPS and ConA stimulation, respectively. Flow cytometric analysis of peripheral blood lymphoid cells showed a significant reduction of the mean proportion surface immunoglobulin positive cells in the flumequine-treated animals. It is concluded that flumequine enhances proliferation of lymphoid cells (probably surface immunoglobulin negative cells) in eel under the present experimental conditions.

In two experiments with European eel (Anguilla anguilla L., 1758) the effects of flumequine (FQ), oxytetracycline (OTC) and furazolidone (FZ) on peripheral blood leucocytes were tested using measurements of differential white blood cell counts in blood smears, flow cytometry and respiratory burst activity of adherent cells. Results revealed that FQ and OTC affected (different) leucocyte populations, whereas no effect of FZ was detected in these experiments. These effects should be taken into account when drugs are registered for official approval in veterinary (fish) medicine.