Centre for Conservation Ecology and Environmental Science, School of Applied Sciences, Bournemouth University, Poole BH12 5BB, U.K.
J Fish Biol. 2014 Jun;84(6):1926-39. doi: 10.1111/jfb.12409.
The effects of number of fish that are aged and scale sub-sampling strategies on the precision of estimates of mean age-length increments from populations of Rutilus rutilus, Leuciscus leuciscus and Leuciscus cephalus were tested. Analyses used data derived from river fish communities in eastern England, U.K.. Regarding the number of fishes analysed in each age group, for each species and mean fork-length increment at age, significant relationships were detected between sample size (n) and the coefficient of variation of the mean (Z) and mean length increment x‾ and measured variance (s(2)). This enabled calculation of the number of scales for producing a mean length increment at age according to n=ax‾(b(-2))Zx‾(-2). Outputs indicated that the number of scales requiring ageing increased substantially as precision increased, but with little variation between species per age category. Ageing between seven and 12 scales per age group would thus provide estimates at 10% precision. As the ages of fishes are not known in advance of scale ageing, the effect of scale sub-sampling regime on precision was also tested using randomized strategies of 10 fish per 5 mm, five per 5 mm, three per 5 mm, 10 per 10 mm, five per 10 mm and three per 10 mm. These were applied to the datasets and the consequences of their reduction in the number of scales for precision were determined using Z=a(0.5)x‾((b/2)(-1))n(-0.5). When compared to no sub-sampling, three per 10 mm always significantly reduced data precision, whereas 10 per 5 mm never significantly reduced precision. These outputs can thus be applied to the design of fish sampling protocols where age and growth estimates are required, with the randomized sub-sampling likely to be the most useful strategy.
测试了鱼类年龄的数量和鳞片亚抽样策略对估算 Rutilus rutilus、Leuciscus leuciscus 和 Leuciscus cephalus 种群平均年龄-长度增量的精度的影响。分析使用了来自英国英格兰东部河流鱼类群落的数据。关于每个年龄组中分析的鱼类数量，对于每个物种和平均叉长增量，在样本量（n）和平均变异系数（Z）与平均长度增量 x‾ 和测量方差（s(2)）之间检测到显著关系。这使得可以根据 n=ax‾(b(-2))Zx‾(-2)计算出产生年龄平均长度增量所需的鳞片数量。结果表明，随着精度的提高，需要老化的鳞片数量大幅增加，但每个年龄类别之间的物种变化很小。因此，每个年龄组龄 7-12 片鳞片可以提供 10%精度的估计。由于在鳞片老化之前不知道鱼类的年龄，因此还使用随机化策略测试了鳞片亚抽样方案对精度的影响，10 条鱼/5 毫米、5 条鱼/5 毫米、3 条鱼/5 毫米、10 条鱼/10 毫米、5 条鱼/10 毫米和 3 条鱼/10 毫米。将这些应用于数据集，并使用 Z=a(0.5)x‾((b/2)(-1))n(-0.5)确定它们减少鳞片数量对精度的影响。与不进行亚抽样相比，3 条鱼/10 毫米总是显著降低数据精度，而 10 条鱼/5 毫米从不显著降低精度。因此，这些输出可以应用于需要年龄和生长估计的鱼类采样协议的设计，随机亚抽样可能是最有用的策略。
