Isabel Boavida

Assessment of instream structures for habitat improvement for two critically endangered fish species

The number of fish habitat improvement schemes has greatly increased in response to the widespread degradation of aquatic ecosystems. However, many of these enhancement projects often fail to create expected habitat conditions, because they are rarely planned and executed with inputs from the species’ habitat requirements throughout their life histories, and it is frequently assumed that the implementation of a specific instream structure for habitat improvement will always benefit all species present. Using a 2D hydraulic model, the present study evaluates the potential habitat improvement for two critically endangered fish species—the Southwestern arched-mouth nase Iberochondrostoma almacai and the Arade chub Squalius aradensis—resulting from simulating the introduction of different instream structures (islands, lateral bays, and deflectors) in a modified Mediterranean river reach. The introduction of islands in the river channel was found to be the best improvement measure for YOY and juvenile nase and chub, as shown by increases in the mean annual Weighted Usable Area (WUA) of more than 100 and 50%, respectively, compared to the present conditions. On the other hand, the simulation with current deflectors proved to be the worst scenario, particularly for nase, with mean annual WUA decreasing by 3.6, 17.8 and 22.7% for YOY, juveniles and adults, respectively. The findings of this study point to the need to account for different species life-history stages when modelling the implementation of instream structures for habitat improvement and also provide a sound basis for future conservation-related studies conducted in Mediterranean rivers that harbour other threatened “sister” species.

Fulfilling spawning flow requirements for potamodromous cyprinids in a restored river segment

The Baixo Sabor hydroelectric scheme was recently constructed (began operating in 2015), blocking fish migration immediately at the river mouth. As a compensation measure for spawning habitat loss the Vilariça River which confluences with Sabor River, immediately downstream from the Baixo Sabor scheme, was chosen for rehabilitation site as an attempt to replace the spawning grounds lost in Sabor River for the potamodromous cyprinid Iberian barbel (Luciobarbus bocagei). Restoration activities included: placement of submerged weirs with fish ramps to increase the lotic/lentic sequence, bank reinforcement, boulder placement and river water profile increase. Water from the nearest reservoir was channeled underground to the lower Vilariça River in order to increase the water flow. The most appropriate volume of water was determined by means of a 1D model coupled with the CASiMiR to determine the weighted usable area for barbel spawners. Nine spawning grounds were identified. Fish migrations began in mid-April when water temperature increased (c. 16°C) and water flow decreased. Barbel tend to spawn in coarse substrate with shallow water and moderate current. Ontogenetic differences in habitat use were reported, with barbel juveniles preferring weaker currents and deeper zones when compared to spawners. Females also display different preferences, which are more apparent after spawning. Both life-stages exhibit the maximum habitat suitability at c. 1.5m3/s. The habitat model used in this study was able to accurately predict the occurrence of spawning grounds, representing, therefore, a valuable decision-making support tool for river managers.

Do artificial velocity refuges mitigate the physiological and behavioural consequences of hydropeaking on a freshwater Iberian cyprinid?: Do refuges mitigate the consequences of hydropeaking on a cyprinid?

Civil Engineering Research and Innovation for Sustainability, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049‐001, Lisboa, Portugal Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349‐017, Lisboa, Portugal Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada 4 Institute of Environmental Science, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada Correspondence M.J. Costa, Civil Engineering Research and Innovation for Sustainability, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049‐001, Lisboa, Portugal. Email: mariajcosta@tecnico.ulisboa.pt Funding information Canada Research Chairs; Fundação para a Ciência e a Tecnologia, Grant/Award Numbers: SFRH/BD/52517/2014 and SFRH/ BPD/90832/2012; Horizon 2020 Framework Programme, Grant/Award Number: 727830; Instituto Superior Técnico, Grant/Award Number: BI209/2016