Treatment of Cyprinus carpio L. and Clarias gariepinus (Burchell) embryos with formalin and malachite green: effect of concentration and length of treatment on their survival.

Malachite green and formalin were investigated as prophylactic dip treatments for developing embryos of Cyprinus carpio and Clarias gariepinus. Based on the findings, recommendations are made on the respective concentrations to be used and exposure periods to be followed for both formalin and malachite green for both fish species.

Investigations into the effects of concentration and duration of exposure to formalin and malachite green on the survival of the larvae and juveniles of the common carp Cyprinus carpio L. and the sharptooth catfish Clarias gariepinus (Burchell).

Prophylactic dip treatments using formalin and malachite green were applied to 4-day old larvae and 12- and 20-day old juveniles of the European common carp, Cyprinus carpio and the African sharptooth catfish, Clarias gariepinus. Treatments consisted of 100 mg/l malachite green for exposure periods of 10, 30 or 90 s and 200 mg/l formalin, administered for 30, 60 or 90 min. Larvae and juveniles of C. gariepinus could be treated with 100 mg/l malachite green for 10 s, or with 200 mg/l formalin for 30 min, with minimum mortalities. Both chemicals affected the survival of the C. gariepinus juveniles, especially the 90 min exposure to formalin. Juveniles of both species were extremely sensitive to 100 mg/l malachite green concentrations.

Some observations on the narcotizing ability of electric currents on the common carp Cyprinus carpio.

Some effects of alternating current electronarcosis and of rectified current electronarcosis on C. carpio were investigated. In all instances recovery from narcosis was accompanied by convulsive spasms. Haemorrhaging of the gills was also observed to occur. Carp do not appear to be suitable candidates for electronarcosis.

The use of electronarcosis as anaesthetic in the cichlid, Oreochromis mossambicus (Peters). III. The effects of changing physical and electrical parameters on the narcotizing ability of half-wave rectified currents.

The narcotizing potential of various rectified current configurations on Oreochromis mossambicus was investigated. A 50 Hz, 200 Vp. half-wave rectified current, applied for 30 s, was found to be a suitable configuration for electronarcosis.

The use of electronarcosis as anaesthetic in the cichlid, Oreochromis mossambicus (Peters). II. The effects of changing physical and electrical parameters on the narcotizing ability of alternating current.

The effects of wave form, voltage, frequency and current as well as application time on the narcotizing ability of alternating current were investigated. A 60 Vrms, 50 Hz sine wave current applied for 30 s produced narcosis of sufficient duration to enable handling and blood sampling. A triangle wave form was inferior in narcotizing ability to both sine wave and square wave forms. Duration of narcosis increased with increasing water conductivity but was reduced by increasing water temperatures.

The use of electronarcosis as anaesthetic in the cichlid, Oreochromis mossambicus (Peters). I. General experimental procedures and the role of fish length on the narcotizing effects of electric currents.

Procedures to narcotize fish by means of alternating or direct electrical currents are described and a method of evaluating the narcotic effects on fish of electrical currents is detailed. The role of fish length on the narcotizing potential of electrical currents was investigated. The results indicate that there is a positive correlation between fish length and the duration of narcosis.

Some observations on the influence of stress on ECG patterns in Oreochromis mossambicus and Cyprinus carpio.

Electrocardiograms of undisturbed, resting fish as well as disturbed (stressed) fish were recorded by biotelemetry. Both fish species showed marked changes in heartbeat patterns in response to stress with tilapia exhibiting the most pronounced changes. A theory is advanced to account for the marked changes in electrocardiogram patterns of disturbed fishes.

Thrombelastographic diagnosis of blood coagulation in two freshwater fish species.

Blood coagulation in two freshwater fish species was investigated by thrombelastography. This indicated that the process in fish is similar to that of humans and mammals, involving the same three basic processes, i.e. extrinsic and/or intrinsic thromboplastin generation, the conversion of prothrombin in thrombin and the formation of fibrinogen to fibrin. Calcium is essential for these reactions to occur.

A thrombelastographic study of the effect of stress on the blood coagulation in Cyprinus carpio (Cyprinidae) and Oreochromis mossambicus (Cichlidae).

The normal blood coagulation in Cyprinus carpio and Oreochromis mossambicus was investigated by thrombelastography and standard thrombelastographs were obtained for each species. The effect of stress on blood coagulation was thereafter determined. The thrombelastograms indicated hypercoagulability under stress conditions. A prominent observation is the differences in the elasticity of the clot under various conditions. Fibrinolysis occurred in all cases, except in the case of Cyprinus carpio after severe agitation for 30 min. Relevant values for various parameters are given.

Trout mortalities as a result of Streptococcus infection.

Excessive mortalities were experienced in the bigger rainbow trout (Salmo gairdneri) at an efficiently managed trout farm. All tests for known toxins in the feed and water proved to be negative. A faecal Streptococcus which belongs to the Lancefield group D but which could not be identified as belonging to any of the recognized species within this group, was isolated from the spleens, livers and kidneys of affected fish. Pathogenicity studies with this organism proved it to be highly fatal to trout but not to Mozambique bream (Sarotherodon mossambicus), banded bream (Tilapia sparrmenii), carp (Cyprinus carpio) or largemouth bass (Micropterus salmoides). The isolation and biochemical characteristics of the organism are described. The symptoms, gross- and histopathology of this disease are described and discussed. The disease resembles a haemorrhagic septicaemia and appears to be associated with intensification and conditions of stress.