Electrofishing removal sampling is a common method for abundance estimation of juvenile salmonids in streams and is usually performed during autumn. European guidelines specify that sampling should be conducted at water temperatures ≥ 5 °C, but studies investigating the validity of sampling below this threshold are lacking. We conducted electrofishing experiments during autumn and winter in three Norwegian rivers, comparing abundance estimation accuracy, rate of fish emigration from electrofishing sites, and mortality for juvenile Atlantic salmon Salmo salar and brown trout Salmo trutta. Abundance estimates were significantly more accurate during autumn than during winter, less accurate for age-0 fish than for older parr, and more accurate when the number of electrofishing passes was increased. By digging through the substrate after electrofishing, we found that a higher proportion of fish were uncatchable during winter than during autumn, and that age-0 fish were more likely than older fish to be uncatchable. For salmon older than age-0, both autumn and winter sampling consistently yielded relatively accurate abundance estimates. However, the rate of fish emigration from electrofishing sites was significantly higher during autumn than during winter and if block nets are not used, emigration during autumn sampling could cause severe underestimation of Atlantic salmon abundance. Fish mortality did not differ between autumn and winter sampling and was low for both species and all age groups. We recommend the use of block nets and conducting five electrofishing passes to reduce the likelihood of severe estimation error.

电捕捞取样是估算溪流中幼鲑鱼丰度的常用方法，通常在秋季进行。欧洲指南规定采样应在水温 ≥ 5 °C 时进行，但缺乏调查低于此阈值采样有效性的研究。我们在秋季和冬季在挪威的三条河流进行了电捕鱼实验，比较了大西洋鲑鱼Salmo salar和褐鳟Salmo trutta的丰度估计准确性、鱼类从电捕鱼地点的迁徙率以及死亡率。秋季的丰度估计明显比冬季更准确，0 龄鱼的准确度低于老年帕尔，而当电钓次数增加时，丰度估计的准确度更高。通过电捕鱼后挖掘基质，我们发现冬季钓不到的鱼的比例高于秋季，而且0龄鱼比年龄较大的鱼更容易钓不到。对于 0 龄以上的鲑鱼，秋季和冬季采样始终得出相对准确的丰度估计值。然而，秋季从电捕捞地点的鱼类迁徙率明显高于冬季，如果不使用拦网，秋季采样期间的迁徙可能会导致大西洋鲑鱼丰度的严重低估。秋季和冬季取样之间的鱼类死亡率没有差异，并且两个物种和所有年龄组的死亡率都很低。我们建议使用拦网并进行五次电钓，以减少严重估计错误的可能性。