Short-term response of fish assemblages to instream habitat restoration in heavily impacted streams

Abstract

Habitat homogenization has been a major impact in stream ecosystems, and it is considered one of the main drivers of biotic homogenization as well, leading to the loss of water quality and fish diversity. In this study, we added artificial woody structures and leaf packs in physically impacted streams to test if the additions can improve habitat complexity and change the taxonomic and functional structure of fish communities. The experiment was done in eight streams impacted by siltation, deforestation, and habitat homogeneization, inserted in an agricultural landscape from the Upper Paraná River Basin, and lasted 112 days. The provision of artificial microhabitats increased instream habitat diversity by creating patches of organic matter deposits, changing flow, and providing substrate for grass colonization of the instream habitat. The experimental manipulation also changed fish species abundance. Nine species contributed to these changes, five decreased and four increased in abundance, indicating species responded differently to the experimental manipulation. However, overall species richness, diversity, and community functional traits remained unaltered. These results indicate that short-term habitat restoration on a local scale may not be enough to promote changes in fish community attributes of streams that are heavily impacted.

Centenary shipwrecks reveal the limits of artificial habitats in protecting regional reef fish diversity

“…Their benefits at the local scale may hide disadvantages at the regional level. The deliberate sinking of new artificial structures at the sea bottom should be done with caution after exhausting all possibilities of conserving and restoring the natural reefs (Carr & Hixon, 1997;Manzotti et al, 2020). Artificial reefs should not be implanted close to natural reefs, rocky shores or in islands with pristine reef ecosystems.…”

“…The structures may be beneficial to some species and detrimental to others. Additionally, they can disrupt species interactions, favour biological invasion and create novel ecosystems (Connell & Glasby, 1999;Manzotti et al, 2020;Mercader et al, 2019;Palmer et al, 2010). From an ecological perspective, it is critical to understand how these structures interact with the remaining biota and the spatial and temporal scales at which their positive and negative effects disappear.…”

Relative importance of meso‐ and microhabitat features in the within‐reach spatial distribution of size‐structured fish assemblages in small streams

“…fallen trees) also induces changes in the channel morphology by deflecting the stream flow. Furthermore, fine woody debris contributes directly to microhabitat diversity (Manzotti et al, 2020). A heterogeneous channel that contains deeper pools shaded by tree foliage ensures a better chance for the fish to survive extreme drought periods.…”

Urbanization impacts water quality and the use of microhabitats by fish in subtropical agricultural streams

“…Using this information, we can identify optimal local conditions and habitat configurations (Marini et al 2019) that could be useful in the effective design of restoration and monitoring programmes (Informe Anual Estratégico 2017). For instance, restoration practices that include artificial structures as refuges or hydrological changes can improve habitat complexity and may promote changes in the fish assemblage in the long term when combined with other actions such as improvements to water quality, riparian cover or the control of soil erosion (Manzotti et al 2020). On the other hand, we consider that future work in this area should focus on the quantitative evaluation of microhabitat components, such as the biomass and life forms of macrophytes, which may better explain the use of these microhabitats by fish.…”