Accounting for spatial variability in the design of sampling programmes for Chaoborus larvae

We developed a model to estimate the number of net hauls (n) needed to quan tify the mean abundance (m) of vertically migrating species of Chaoborus la rvae (C. flavicans, C. punctipennis and C. trivittatus) in the entire pelag ic zone of lakes at a specified level of precision (D = SE/m, where SE is t he standard error). The model was n = 1.94m(-0.30) D (2). It was derived by combining Taylor's power law with a model that estimated sample size (i.e. number of net hauls) for a specified level of precision. The model indicat es that for a typical temperature lake Chaoborus population of 50 larvae m( -3), 15 net hauls are required to obtain a precision of 0.2. As the precisi on of a single pelagic, vertical haul is only 0.77 at such typical Chaoboru s densities, caution should be exercised in assessing the role of Chaoborus in food webs using data based on the traditional approach to plankton samp ling, i.e. one mid-lake station.