The potential use of clove oil (eugenol) as an anaesthetic for Atlantic salmon Salmo salar, brown trout Salmo trutta, rainbow trout Oncorhynchus mykiss, whitefish Coregonus lavaretus, perch Perca fluviatilis and roach Rutilus rutilus was examined at 5, 10, 15 and 20 C using three anaesthetic concentrations (varying from 20 to 200 mg l À1 ) at each temperature. Substantial species differences in sensitivity to clove oil were observed, even amongst congeners, and there may be some disadvantages (slow recovery and possibly mortality) with using clove oil for 0þ year whitefish and at low temperatures for perch and roach. # 2004 The Fisheries Society of the British Isles

The e¡ects of weekly anaesthetization with clove oil and tricaine methanesulphonate (MS-222) on feed intake and growth were examined in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), held individually. Repeated handling without anaesthetics signi¢cantly reduced feed intake and weight gain compared with an unhandled control group during an 8-week experiment.When anaesthetics were used during handling the feed consumption and weight gain were signi¢cantly (MS-222) or not signi¢cantly (clove oil) higher than in ¢sh handled without anaesthesia. When compared with the unhandled control group, neither of these two anaesthetics had signi¢cant e¡ects on feed intake but, in contrast to MS-222, repeated anaesthesia with clove oil had a signi¢cant negative e¡ect on growth. However, the e¡ects of MS-222 and clove oil on the growth were not sig-ni¢cantly di¡erent from each other. Feed conversion ratio (feed/gain) of MS-222-anaesthetized ¢sh was signi¢cantly higher compared with unhandled control and handled control ¢sh but was not signi¢cantly di¡erent from ¢sh anaesthetized with clove oil. These results suggest that both MS-222 and clove oil alleviate handling stress in juvenile rainbow trout, and that these two anaesthetics are rather similar with respect to their e¡ects during repeated exposures.

No abstract

Inhibitory concentrations of clove oil and ethanol against growth of Saprolegnia sp. hyphae were screened by a modification of the hemp (Cannabis sativa L.) seed MicroPlate (HeMP) method and their usability as antifungal agents during incubation of rainbow trout Oncorhynchus mykiss eggs was tested. In vitro experiment showed that in continuous static exposure, clove oil at 100 mg L À1 significantly inhibited the growth of Saprolegnia, whereas in bath exposures, clove oil at 500 mg L À1 had no significant effect at any exposure time tested (15, 60 and 240 min), but clove oil at 10 000 mg L À1 significantly inhibited growth at all exposure times. Clove oil and ethanol treatments had no visible effects on the onset or spread of the fungus during incubation of rainbow trout eggs. Clove oil at 1000 mg L À1 resulted in 95-100% mortality before the eyed stage was reached. Sublethal concentrations of clove oil and ethanol had no effects on the development rate of the embryo or growth and yolk utilization efficiency after hatching. This study suggests that clove oil and ethanol may not be options in controlling aquatic fungi infestations during incubation of rainbow trout eggs.