The effects of temperature (11, 15, and 20°C) on clove‐oil‐induced anesthesia in fry of steelhead Oncorhynchus mykiss (0.18 ± 0.01 g [mean ± SE]) were evaluated at 25, 50, and 100 mg clove oil/L. Induction time decreased significantly with increasing temperature and dose. Recovery time after removal from anesthesia decreased significantly with increasing temperature. Mortality at 24 h postanesthesia increased significantly with increasing temperature and dose. Although clove oil appears to be an effective general anesthetic for salmonid fry, the data indicate that care must be taken in determining the appropriate dose to minimize temperature‐associated mortality.

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This study examined the pH sensitivity of steelhead, Oncorhynchus mykiss (Walbaum), sperm motility relative to the composition of incubation and activation media. The percentage of sperm that initiated motility following incubation in a sperm immobilizing solution (SI) titrated to different pH values and subsequent activation by dilution in buffered swimming medium (SM) at pH 8.5 or 50% ovarian fluid (OF) showed little or no pH sensitivity; sperm diluted in de‐ionized water (DI) showed no motility after incubation at any pH. In contrast, motility of sperm diluted in tap water (TAP) was highly sensitive to the pH of the incubation medium. Sperm incubated with buffered seminal plasma at high, but not low pH demonstrated high percent motility when diluted with DI. Sperm incubated in low‐pH SI demonstrated high motility only when diluted into high‐pH SM. The effects of the composition of incubation and activation media on sperm motility were generally reflected in comparable effects on fertility. Therefore, these data indicate that the pH sensitivity of sperm motility and fertility depends on the composition of commonly used incubation as well as activation media.

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This study examined the direct impact of three commonly used anesthetics-clove oil (86% eugenol), tricaine (tricaine methanesulfonate ), and CO 2 -on egg quality for steelhead Oncorhynchus mykiss and that of clove oil and tricaine on the motility of sperm from both steelhead and white sturgeon Acipenser transmontanus. Exposure of unfertilized eggs for 6 or 24 h to 150 mg clove oil/L, 225 mg tricaine/L, or less than 100 mm Hg CO 2 resulted in no reduction in egg fertility or embryo survival to hatch. However, higher doses (1,500 mg clove oil/L; 2,250 and 22,500 mg tricaine/L; or more than 125 mm Hg CO 2 ) negatively impacted egg quality. Similarly, a 3-h exposure to clove oil (150 mg/L) or tricaine (225 mg/L) produced no significant effect on sperm motility in steelhead. White sturgeon sperm showed a modest decline in motility after incubation in clove oil. Thus, the data suggest that clove oil and tricaine can be used on fish prior to gamete harvesting without significant adverse impacts on gametes. Although CO 2 is unlikely to have deleterious effects on eggs, CO 2 -associated declines in ovarian fluid pH may be of concern when ovarian fluid pH is used as an indicator of egg quality.