J. Limnol., 2014; 73(s1): 171-185 DOI: 10.4081/jlimnol.2014.826 INTRODUCTION Trophic links characterize energy flow and describe how individuals, populations and species interact in food webs. Their non-random, structured patterning begets sta- bility and persistence of complex communities (Yodzis, 1981; De Ruiter et al., 1996; Neutel and Heesterbeek, 2002), underlies ecosystem functioning (Brose et al., 2012) and mediates the impact of human disturbance including climate change (Dossena et al., 2012; Lurgi et al., 2012) and commercial fisheries (Frank et al., 2005; Garcia et al., 2012). In marine and freshwater ecosystems, feeding links are thought to dominate over other biotic interactions, such as mutualism or competition for space (Woodward, 2009). Knowledge of the factors that determine the presence and strength of trophic links is therefore crucial for our under- standing of food webs and community dynamics in aquatic habitats. Various metrics of interaction strengths in food webs exist (Berlow et al., 2004). This paper focuses on quantitative descriptors of individual trophic links: preda- tion rates and prey selectivity. Building upon the seminal works of Kleiber (1932) and Peters (1983), body size is used to describe predator-prey interactions (Brose et al., 2006; Petchey and Dunne, 2012) as well as other properties of individuals, populations and communities (Brown et al., 2004; Woodward and Warren, 2007; Sibly et al., 2012). Body size underpins biomass growth and energy transfer in aquatic habitats (Edgar, 1990) and size-based metrics describe well the structure and func- tion of entire aquatic ecosystems (Hildrew et al., 2007; Rudolf and Rasmussen, 2013). Community size spectra are also sensitive to natural and human-driven disturbances (Brucet et al., 2005; Solimini et al., 2005; Emmrich et al., 2011) and can be used in environmental monitoring (Basset et al., 2012; Garcia et al., 2012). Size-based views are thus particularly prominent in aquatic ecology and studies of freshwater food webs gen- erated some of the most detailed datasets elucidating the role of body size in community structuring (Woodward and Hildrew, 2002). Most data, however, come from run- ning waters (Gilljam et al., 2011). Food webs in standing waters remain less studied (Woodward et al., 2005) and we currently rely on a limited body of direct, sufficiently detailed evidence of their topology and the distribution of trophic link strengths. In one of the first studies, Havens (1992) analysed the connectance of pelagic food webs in 50 small lakes and ponds in New York state; his cumula- tive web approach combined field surveys of species com- position with information on their diet gleaned from the literature, which omitted potential variation between habi- tats and trophic link strengths. Few datasets have been Trait- and size-based descriptions of trophic links in freshwater food webs: current status and perspectives David S. BOUKAL 1,2* 1 University of South Bohemia, Faculty of Science, Department of Ecosystems Biology, České Budějovice; 2 Biology Centre AS CR, vvi, Institute of Entomology, Laboratory of Aquatic Insects and Relict Ecosystems, České Budějovice, Czech Republic *Corresponding author: boukal@entu.cas.cz ABSTRACT Biotic interactions in aquatic communities are dominated by predation, and the distribution of trophic link strengths in aquatic food webs crucially impacts their dynamics and stability. Although individual body size explains a large proportion of variation in trophic link strengths in aquatic habitats, current predominately body size-based views can gain additional realism by incorporating further traits. Functional traits that potentially affect the strength of trophic links can be classified into three groups: i) body size, ii) traits that identify the spatiotemporal overlap between the predators and their prey, and iii) predator foraging and prey vulnerability traits, which are readily available for many taxa. Relationship between these trait groups and trophic link strength may be further modified by pop- ulation densities, habitat complexity, temperature and other abiotic factors. I propose here that this broader multi-trait framework can utilize concepts, ideas and existing data from research on metabolic ecology, ecomorphology, animal personalities and role of habitats in community structuring. The framework can be used to investigate non-additive effects of traits on trophic interactions, shed more light on the structuring of local food webs and evaluate the merits of taxonomic and functional group approaches in the description of predator-prey interactions. Development of trait- and size-based descriptions of food webs could be particularly fruitful in limnology given the relative paucity of well resolved datasets in standing waters. Key words: predator-prey interactions, body size, foraging, vulnerability, habitats, spatiotemporal distribution. Received: June 2013. Accepted: October 2013. Non-commercial use only