Silurus

Abstract: Summary Gutted European catfish (Silurus glanis) from warm-water aquaculture was stored in ice for 30 days. The limit of saleability was reached after approximately 20 days, and cooked fillets became inedible after about 27 days. Quality changes were investigated using established analytical methods; pH, total volatile bases (TVB), thiobarbituric acid number and texture measurements by Instron were not usefully predictive of shelf-life or possible storage time. The Fish Tester and Torrymeter values decreased from 848 to 376 and 111 to 61, respectively. On day 27 the total aerobic bacterial counts had reached some 108/cm2 skin surface but only 105/g muscle. Hypoxanthine concentrations increased steadily to 17.2 mg/100 g, and ammonia levels increased from 11.5 to 18.7 mg/100 g muscle. There were no differences in the patterns obtained by isoelectric focusing of sarcoplasmic proteins from fresh and spoiled European catfish.

Abstract: Ovulation was stimulated in four groups of European catfish, Silurus glanis L., using injections of des-Gly10, [D-Ala6]-LHRH Ethylamide (20 μg kg–1) and pimozide (10 mg kg–1), Ovaprim (0.33 mL kg–1), and carp pituitary extract (4 mg kg–1, in one or two doses). A higher percentage of ovulating females (producing eggs of sufficient quality) was found after the LHRH-a and Ovaprim treatments (100% and 80%) in relation to fish treated with the pituitary extract (60% and 66.67%). The greatest weight of eggs was obtained in the case of repeated hypophysation and LHRH-a (1299.69 and 1298.57 g, respectively), and the smallest after single hypophysation (1144.08 g). After 60 h of incubation, the best quality of eggs was found in the group treated with Ovaprim (62.9% of live embryos) and the poorest in the two groups which underwent hypophysation (50.41% and 50.75%). No statistically significant effect by the ovulation stimulators on the characteristic qualitative and quantitative traits of obtained eggs was ascertained.