Boudreau Stephanie A, Yan Norman D
Department of Biology, York University, Toronto, Ontario, Canada.
Environ Monit Assess. 2004 Feb;91(1-3):17-26. doi: 10.1023/b:emas.0000009228.09204.b7.
We tested the sampling methods of a volunteer-based monitoring program designed to detect the non-indigenous spiny water flea, Bythotrephes longimanus, and found that the program could detect the majority of Bythotrephes invasions. Volunteers take two vertical hauls with a 30 cm diameter net at each of three pelagic stations. To determine if the volunteers were using a large enough net at their three stations, we performed a 17-lake comparison of the volunteer's net with a 75 cm diameter, research-grade net. We found no difference in the number of stations at which Bythotrephes was detected (paired t-test, p = 0.155) with the two nets, because Bythotrephes densities were above the detection limits for both nets. To determine if three stations were sufficient to detect the invader with the volunteer's net, we deployed it at 30 stations in two lakes with average (Harp Lake, 4.17 Bythotrephes m(-3)) vs. low Bythotrephes densities (Sugar Lake, 0.92 m(-3)). In Harp Lake, repeated randomized sampling of the 30 sets of data indicated that only three stations were needed for 100% capture success. In Sugar Lake, seven stations were needed for 100% capture success, but three stations, the current program design, failed to detect the invasion only 14% of the time.
我们对一个旨在检测外来物种长刺水蚤的基于志愿者的监测项目的采样方法进行了测试，发现该项目能够检测到大多数长刺水蚤的入侵情况。志愿者在三个中上层站点各使用一个直径30厘米的网进行两次垂直拖网采样。为了确定志愿者在其三个站点使用的网是否足够大，我们将志愿者使用的网与一个直径75厘米的科研级网在17个湖泊中进行了比较。我们发现，用这两种网检测到长刺水蚤的站点数量没有差异（配对t检验，p = 0.155），因为长刺水蚤的密度高于两种网的检测限。为了确定三个站点是否足以用志愿者的网检测到入侵者，我们在两个湖泊的30个站点部署了该网，其中一个湖泊长刺水蚤密度平均（哈普湖，4.17只/立方米），另一个湖泊长刺水蚤密度较低（糖湖，0.92只/立方米）。在哈普湖，对30组数据进行重复随机抽样表明，仅需三个站点就能实现100%的捕获成功率。在糖湖，需要七个站点才能实现100%的捕获成功率，但按照当前项目设计的三个站点，只有14%的时间未能检测到入侵。
