Formalin treatments before eyeing and hand-picking of Arctic charr (Salvelinus alpinus) eggs – re-evaluating the timing of antifungal treatments

Arctic charr (Salvelinus alpinus) eggs in hatcheries are treated for fungal infections using formalin before, and hand-picking during the eyed stage. The relative effectiveness of the treatments was evaluated using a factorial design with the application of weekly hand-picking, and formalin treatments at 380 ppm for 13 minutes three times weekly as factors. The effects of the treatments on total mortality and hatching success were compared using a two-way ANOVA. Both treatments exhibited significant, positive effects on egg survival. Hand-picking during the eyed stage (+ 0.5 to 2.5 % survival to hatch) was found to be more effective than formalin treatments before (+ 0.0004 to 0.8 % survival to hatch). This is likely due to differences in the timing of administration of the treatments. The probability of fungal infections is indicated to vary with time, and a peak seemed to occur at hatch.

孵化场中的北极红点鲑（Salvelinus alpinus）卵会在眼发育期前使用福尔马林（formalin）处理真菌感染，并在眼发育期开展人工挑拣。本研究采用析因设计评估上述两种处理方式的相对有效性，实验因素设置为每周1次人工挑拣，以及以380ppm浓度福尔马林每周施用3次、每次13分钟的处理。采用双因素方差分析（two-way ANOVA）比较两种处理对总死亡率及孵化成功率的影响。结果显示，两种处理均对卵存活具有显著正向作用；眼发育期人工挑拣可使孵化存活率提升0.5%至2.5%，其效果优于孵化前的福尔马林处理（仅可提升0.0004%至0.8%的孵化存活率）。该差异或源于两种处理的施用时机不同。研究表明，真菌感染概率随时间动态变化，且在孵化阶段似乎存在感染峰值。