Fish colonization of artificial reefs in a large Neotropical reservoir: material type and successional changes

Abstract

Abstract. Artificial reefs have barely been used in Neotropical reservoirs (about five studies in three reservoirs), despite their potential as a fishery management tool to create new habitats and also to understand fish ecology. We experimentally assessed how reef material (ceramic, concrete, and PVC) and time modulated fish colonization of artificial reefs deployed in Itaipu Reservoir, a large reservoir of the mainstem Parana´River, Brazil. Fish richness, abundance, and biomass were significantly greater in the reef treatments than at control sites. Among the experimental reefs, ceramic followed by the concrete treatments were the materials most effectively colonized, harboring the majority of the 13 fish species recorded. Although dependent on material type, many of the regularities of ecological successions were also observed in the artificial reefs, including decelerating increases in species richness, abundance, mean individual size, and species loss rates with time and decelerating decreases of species gain and turnover rates. Species composition also varied with material type and time, together with suites of life history traits: more equilibrium species (i.e., fishes of intermediate size that often exhibit parental care and produce fewer but larger offspring) of the Winemiller-Rose model of fish life histories prevailed in later successional stages. Overall, our study suggests that experimental reefs are a promising tool to understand ecological succession of fish assemblages, particularly in tropical ecosystems given their high species richness and low seasonality.

The role of submerged trees in structuring fish assemblages in reservoirs: two case studies in South America

“…In the case of the Itaipu Reservoir, it was possible to verify the decrease in the fish richness and diversity in habitats without submerged trees during the first years, a pattern that, as recorded for the CPUE, suggests, as mentioned, a period of the fauna adjustment in the new environment. An experiment conducted by Santos et al (2011b) in which artificial substrates were installed in one of the regions sampled during the present study (in the Itaipu Reservoir), was in agreement with the patterns observed here. These authors observed that, in the structured regions, the richness, in addition to the abundance and biomass, were higher than those in the non-structured regions, demonstrating the importance of spatial heterogeneity to biodiversity in aquatic environments.…”

“…Therefore, the structuring effect was observed in both studied reservoirs, corroborating the results observed at other latitudes (Sass et al, 2006;Roth et al, 2007) and in studies conducted in South America that examined submerged macrophytes and artificial substrates (Santos et al, 2008(Santos et al, , 2011b. The noticeable increase in the fish preference for submerged trees after the second year, especially in the fifth year, probably originated from the expected instability in new environments and from the time that pre-existing species requires to Hydrobiologia (2012) adjust to the distinct habitats created in the inundated area (Agostinho et al, 1999.…”

“…These authors observed that, in the structured regions, the richness, in addition to the abundance and biomass, were higher than those in the non-structured regions, demonstrating the importance of spatial heterogeneity to biodiversity in aquatic environments. The experiments by Santos et al (2011b) were performed in the 23rd year after the Itaipu Reservoir was formed. However, Mourão Reservoir did not present significant differences between habitats in terms of species richness, evenness, or diversity.…”

Habitat complexity: approaches and future directions

“…Major impacts on biodiversity highlighted in many marine and freshwater studies serve as a rationale for use of the habitat complexity concept in conservation, including the selection of protected areas and habitat enhancement using artificial reefs and other structures (e.g., Bohnsack, 1991;Hunter & Sayer, 2009, Santos et al, 2011. The critical role of habitat complexity is also the reason for growing concern over destruction of complex habitats as a result of fishing activities Hydrobiologia (2012) -Filip et al, 2009;Buhl-Mortensen et al, 2010), as well as over the ocean-wide reduction in habitat-forming organisms due to climate change (Loya et al, 2001;Hoegh-Guldberg & Bruno, 2010).…”

“…The most common restoration measures in streams are habitat enhancements and channel reconfiguration, designed to increase habitat heterogeneity (Palmer et al, 2010). Recently, the potential for using artificial structures made with ceramic, concrete, and PVC to increase fish abundance and diversity was demonstrated in sub-tropical reservoirs (Santos et al, 2011). Similarly, Gois et al (2011, this issue) conclude that keeping the arboreal vegetation in new reservoirs would help in the conservation of the fisheries resources.…”