G. L. Smit

The use of benzocaine-hydrochloride as an aid in the transport of fish

Abstract The potential of benzocaine-hydrochloride as an aid in the transport of fish was investigated. When used at a concentration of 25 mg/l the anaesthetic caused a reduction in the excretion of ammonia and carbon dioxide by the fish, while, as a result of the reduced activities of the fish, the pH and alkalinity values of the transport water remained fairly constant. When benzocaine-hydrochloride was not used, the activities of the fish produced a significant deterioration in water quality evidenced by the accumulation of ammonia and carbon dioxide.

Anaesthetic potency of MS 222 and neutralized MS 222 as studied in three freshwater fish species

Abstract 1. The effects of several different concentrations of MS 222 and neutralized MS 222 on aquarium water quality and anaeshetic potency were investigated in Cyprinus carpio, Sarotherodon mossambicus and Salmo gairdneri. 2. MS 222 caused a decrease in pH and bicarbonate alkalinity with a corresponding increase in pCO2 of the aquarium water. Conductivity was also increased. Neutralized MS 222 prevented, apart from an increase in conductivity, such effects. 3. Increasing the concentration of MS 222 in the aquarium water resulted in a decrease in anaesthetic induction times in all three fish species studied. Neutralized MS 222 induced anaesthesia, reduced induction times further and also increased recovery times from anaesthesia. 4. The amount of free MS 222 in the blood of the three fish species studied did not differ significantly from each other per MS 222 concentration employed and showed an increase with increased concentrations of MS 222. With neutralized MS 222 the concentration of free MS 222 in the blood of the three fish species was generally higher. 5. Neutralized MS 222 thus resulted in a deeper, more consistent anaesthesia, thereby indicating a safer, more effective, longer-acting anaesthetic.

Observations on some effects of disodium ethylenediamine tetra-acetate and heparin on fish blood

Abstract 1. Heparin in NaCl solution, containing 0.15% chlorocresol as preservative and disodium ethyldiamine tetra-acetate (EDTA) powder (dissolved in deionized water), were compared as anticoagulants for the determination of pH, pCO 2 , pO 2 and haematocrit values immediately upon withdrawal and after certain time intervals in the blood of the freshwater fish, Cyprinus carpio . 2. All concentrations of EDTA investigated caused drastic changes in pH, pCO 2 , pO 2 and haematocrit values of blood whereas heparin produced few significant effects. 3. Possible reasons for the observed effects are discussed. It is again stressed that preliminary experiments must be done to examine the effects of anticoagulants prior to routine haematological investigations.

The anaesthetic potency of benzocaine-hydrochloride in three freshwater fish species

Anaesthesia was induced in the common carp, Cyprinus carpio, tiiapia, Oreochromis mossambicus and rainbow trout, Salmo gairdneri, at concentrations of 25; 50; 75 and 100 mg/1 of benzocaine-hydrochloride as well as neutralized benzocaine-hydrochloride at water temperatures of 15; 20 and 25 °C. The results obtained indicated intra-and interspecific differences in the susceptibility of fish to anaesthesia due to metabolic, chemoreceptive and temperature tolerance differences in and amongst the three species.

The effect of heparin concentration on certain blood parameters of the rainbow trout Salmo gairdneri Richardson

Abstract 1. The effect of concentrations of 1, 2, 3 and 4 mg of the anticoagulant heparin per ml blood on the pH, pO2, pCO2, haematocrit and plasma chloride concentration of the blood of the trout Salmo gairdeneri was studied. 2. A concentration of 4 mg heparin/ml blood appeared to have the least effect on most parameters. 3. Plasma chloride concentration, however, appeared to be the least affected by an anticoagulant concentration of 3 mg/ml blood.