Principles & Processes for Assessing Fish Assemblage Condition in Boatable Rivers of Five Continents

Increasingly, researchers and government agencies sample entire fish assemblages to assess ecological condition in entire, large boatable rivers.  Such surveys can involve complex survey and site-scale designs, multiple gears, expensive equipment, the difficulty of capturing rare and spatially discontinuous species, serious funding limitations, and gear selectivity associated with fish species and their sizes and habitats. Clearly, there are trade-offs between spatio-temporal habitat use by fish and appropriate, cost-effective sampling effort. In this presentation, we describe how we used data independently to determine how those opposing factors were resolved for surveying large river fish assemblages on five continents (Asia, Australia, Europe, North America, South America). Then we identify common survey-sampling approaches applicable in all five cases and make recommendations for future surveys regarding site size, number of sites, hydromorphological and biological reach definition, and gear types sufficient for sampling in an integrative manner to account for natural variability and species turnover at smaller spatial scales.