Trophic cascade effects of Hoplias malabaricus (Characiformes, Erythrinidae) in subtropical lakes food webs: a mesocosm approach

Abstract

While the cascading effect of piscivorous fish on the pelagic food-web has been well studied in north temperate lakes, little is known about the role of native piscivores in warm lakes. Here, the fish communities are typically characterized by high abundances of small, omnivorous fish exerting a high predation pressure on the zooplankton. We conducted a 1-month replicated mesocosm experiment at subtropical conditions to test the effects of piscivorous (Hoplias malabaricus) fish on phytoplankton biomass and water transparency. Our experimental design comprised two (phytoplankton ? zooplankton), three (phytoplankton ? zooplankton ? planktivores) and four (phytoplankton ? zooplankton ? planktivores ? piscivores) trophic levels. We designed two different four trophic level treatments, one with juveniles of H. malabaricus (\15 cm) and the other with adults ([30 cm), to evaluate the strength of the effects of juveniles and adults. A major trophic cascade response was observed. In the planktivores treatment, chlorophyll a (Chl a) and turbidity significantly increased, while total zooplankton abundance (especially Daphnia obtusa) and water transparency decreased. In both H. malabaricus treatments and in the two trophic levels control, the opposite pattern was observed; thus, Chl a and turbidity decreased, while zooplankton abundance and water transparency increased. The differences observed reflected the strong control on the planktivore Jenynsia multidentata by both sizes of H. malabaricus, propagating down through the trophic web. Hoplias malabaricus is widely distributed in South America and may, therefore, be a good candidate for restoration by biomanipulation in eutrophic lakes of subtropical and tropical regions. However, detailed investigations at whole-lake scale are needed to determine its potential.

Fish but Not Macroinvertebrates Promote Trophic Cascading Effects in High Density Submersed Plant Experimental Lake Food Webs in Two Contrasting Climate Regions

“…By contrast, in the fish treatments, a cascading effect was revealed by a major reduction of the zooplankton grazing potential and a significant increase in phytoplankton biomass in both climatic zones. Our findings confirm the occurrence of a fish predation-driven structure of zooplankton [2], as suggested also in previous works in subtropical, e.g., [19,26,32,[56][57][58][59][60], temperate, e.g., [61][62][63][64], and even sub-polar systems [65,66].…”

Does the oscillation of the water volume of the reservoir influence in the same way in fish diet?

“…The piscivorous feeding habit of this species in environments of Neotropical regions is well documented in the literature (Corrêa & Piedras, 2008). Experimental studies in the mesocosm have demonstrated that the trahira has an important role in the trophic structuring and regulation of forage species in aquatic environments (Mazzeo et al, 2010). Therefore, this species deserves special attention in studies that seek the conservation of the ichthyofauna in dammed environments, mainly those related to the detritivorous guild, the predominance in the detritus item consumption may be derived of the flooding of a large amount of terrestrial phytomass, which promotes a high production of detritus in reservoirs, as well as depletions in the water level, can favor the growth of grasses and other plants in marginal regions, which with its subsequent submergence, also contribute to detritus production (Agostinho et al, 2007).…”

Feeding patterns, trophic structure and damming rivers effect: studies applied in freshwater environments in the Brazilian semi-arid region

“…Experimental studies in mesocosms show that H. malabaricus plays an important role in trophic structuring and regulation of forage species in aquatic environments (Mazzeo et al 2010). Therefore, this species deserves special attention to studies aimed at the conservation of the ichthyofauna in dammed environments, especially those considered small and medium sized.…”