J.T. Ferreira

Comparison of Anesthetic Potency of Benzocaine Hydrochloride and MS-222 in Two Freshwater Fish Species

Abstract The hydrochloride of ethyl p-aminobenzoate was synthesized and its anesthetic potency compared with that of MS-222 at concentrations of 50,80, and 100 mg/L. The free compound of these agents in fish blood was also determined. The results indicate that benzocaine hydrochloride is a more effective anesthetic than MS-222 at the concentrations applied. It must be pointed out, however, that benzocaine hydrochloride is not registered for fishery use in the United States.

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.

Genetic distances between and evolutionary relationships for Tilapia guinasana, T. rendalli and T. sparrmanii

Abstract Due to the extent of morphological similarities between Tilapia guinasana and T. sparrmanii , the validity of the former species is in question. Tilapia guinasana and T. Sparrmanii were electrophoretically analysed to determine the amount of genetic differences between the species. Tilapia rendalli was included in this investigation because it represents the only other commonly found tilapia in southern Africa. Genetic distances calculated between the species revealed a small genetic distance (values ranged from 0.07 to 0.10) between T. guinasana and T. Sparrmanii and a much larger distance (from 0.51 to 0.76) between the former species and T. rendalli . Sufficient genetic differentiation therefore exist between these species in order to regard each of them as separate species. Evolutionary relatonships inferred by cladistic and phenetic analyses also revealed T. guinasana to be evolutionary closer to T. sparrmanii than to T. rendalli . The results from this study indicate the T. guinasada probably evolved from a population of T. sparrmanii and that this separation occurred approximately 1.19 million years ago.

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.

Genetic variation in the nine rainbow trout (Oncorhynchus mykiss) populations in South Africa

Abstract 1. 1. Twenty-six protein coding loci in nine populations of rainbow trout, from different localities in South Africa, were analyzed by starch and polyacrylamide gel electrophoresis to estimate the amount of genetic diversity present. 2. 2. Heterozygosity ranged between 0.0445 and 0.0745. 3. 3. The relatively high heterozygosity levels are probably due to the historical mixing of strains, and the differences in heterozygosity indicate that the populations originate from different sources, each with different genetical characteristics. 4. 4. Differences in phenotypic characters (i.e. growth) seem to relate to genotypic variation, whilst food conversion rate and survival performance results did not seem to relate to genotypic variation.