Sampling Efficiency of Gerking Sampler and Sweep Net in Pond Emergent Littoral Macrophyte Beds - a Pilot Study

摘要

Modified Gerking box sampler is one of devices used for the collection of aquatic phytophilous macroinvertebrates. The presented modification consists of a metallic frame box and a movable cutter. It was constructed for sampling in hard emergent littoral macrophyte beds. In this pilot study, its efficiency was compared with a frequently used sweep net. Comparative sampling was performed in the same mesohabitat of hard emergent vegetation in littoral zones of three carp ponds during one season (late summer). Sampling with the frame box sampler was more labour consuming, but significantly (P<0.05) more effective in capturing slow-moving or sedentary animals such as gastropods, oligochaetes, leeches, water mites, and chironomid larvae. In contrast, fast-moving invertebrates (water bugs, chaoborid larvae) were significantly (P<0.05) less abundant in samples taken by the frame box compared with sweep net samples. The composition of macroinvertebrate fauna and total numbers of captured individuals varied between methods and among sampling sites. The results showed that the modified Gerking sampler is able to collect all principal higher taxa and, therefore, it is suitable for quantitative monitoring of macroinvertebrates in littoral zones of standing water bodies. Complementary sampling with a sweep net at the same localities is recommendable for better biodiversity assessment.