OOS 2-9
Body size and trophic position in fish assemblages of tropical rivers in the Lower Mekong Basin
Because an animal’s body size influences consumer-resource interactions within the community, it has been used in food web models to predict ecosystem stability, patterns of energy flow, and community response to disturbances such as fishing pressures. A general assumption in food web models about the body-size hierarchy across trophic levels has been widely cited in marine and temperate lake ecosystems, but has rarely been discussed with respect to lotic ecosystems or tropical lakes. In the present study, we examined the association between body length and trophic position of fish assemblages in four lowland rivers of the Lower Mekong Basin in Cambodia.
Results/Conclusions
We found no significant correlation between body size and trophic position based on the regional species assemblage. At the taxonomic level of order, we found significant relationships among species within the orders Siluriformes and Perciformes, but not Cypriniformes. Similarly, at the family level, we found significant correlations within the families Siluridae and Bagridae, but not Cyprinidae. Additional analysis for species within different trophic groups indicated no body size–trophic level correlation for detritivores, omnivores and insectivores, but piscivores had a significant relationship.
Therefore, for species-rich tropical fish assemblages in which there is high incident of detritivory and omnivory, trophic level and body size are very weakly correlated, and body size is not an appropriate surrogate for species when building dynamic food web models.