Inês C. Oliveira

Diadromous fish such as Petromyzon marinus and Alosa alosa support economically and culturally important small‐scale fisheries in Portugal but face increasing pressures such as habitat degradation, climate change, and overexploitation. In response, a voluntary label‐of‐origin system was introduced in selected river basins to enhance product differentiation and improve traceability. This study evaluates the implementation and performance of this initiative in the Mondego and Vouga river basins. A mixed‐methods approach combined analysis of labeling records with stakeholder interviews and questionnaires, complemented by a multi‐criteria assessment of implementation challenges. Results indicate generally positive stakeholder perceptions regarding trust and market valorization; however, adoption remained inconsistent and highly dependent on institutional facilitation. Key constraints included limited traceability information, operational difficulties in tag application, and fragmented governance responsibilities. The findings suggest that while voluntary labeling initiatives may enhance product transparency and perceived value, their effectiveness depends on operational feasibility, regulatory integration, and sustained institutional support. This case study provides empirical insights into the opportunities and limitations of traceability‐based instruments for governance and management in inland small‐scale fisheries.

Habitat loss and overfishing are the most significant threats to diadromous fish, most of them of high socioeconomic and conservationist importance, such as Alosa alosa, Alosa fallax, Petromyzon marinus and Anguilla anguilla. The main objective of the LIFE Águeda project (LIFE16 ENV/PT/000411) is the removal of hydro-morphological pressures towards the reestablishment of conditions for a good ecological status, as required by the Water Framework Directive (WFD) and associated River Basin Management Plans. Actions to achieve the project’s objectives include the restoration of river morphology through the construction of nature-like fish passes, removal of river obstacles and re-naturalization of the riverbed. Aside from these interventions, the project also contemplates riparian habitat restoration, design and operation of a pilot translocation program directed to European eel juveniles, management of recreational and commercial fisheries, and stakeholders’ engagement, safeguarding compatibility of ecosystem uses. To reestablish longitudinal connectivity in rivers Agueda and Alfusqueiro, a total of five fish passes (two modular and temporary vertical-slot and three nature-like fish passes) will be installed in obstacles where current uses need to be secured and removal is not an option. Obsolete or illegally built obstacles are to be completely or partially removed, in a total of eight interventions in both rivers. By placing PIT antennas in the most upstream fishways planned to be built in both rivers, and by monitoring the movements of tagged fish from target species, the efficiency of these habitat restoration actions, and the reestablishment of longitudinal connectivity, will be assessed.

The European river (Lampetra fluviatilis Linnaeus, 1758) and brook (Lampetra planeri Bloch, 1784) lampreys are considered ‘paired species’, i.e., they are closely related and morphologically very similar but have distinct modes of adult life (anadromous vs. resident). In the Iberian Peninsula, the southern limit of both species’ distribution, they face different pressures (e.g., barriers, pollution, hydrological stress) that reduce the available habitat, which is exacerbated by the actual climate change context. The main objective of the present study was to evaluate meso- and microhabitat preferences of Lampetra sp. On the mesohabitat scale, the environmental variables that influence these species’ distributions on the watershed scale were identified. On the microhabitat level, besides identifying the fine-scale variables that influence the presence and abundance of Lampetra sp., possible changes in habitat preferences throughout the larval stage (i.e., distinct size/age classes) were also assessed. Mesohabitat results suggest that the relative abundance of Lampetra sp. is related to variables such as pH and riparian vegetation. Regarding the microhabitat, the relative abundance of the size classes’ distribution seems to be associated with variables such as substrate granulometry. The results in terms of habitat preferences on a Mediterranean basin are discussed in the context of a climate change scenario (e.g., decrease in habitat quality and availability) and management and conservation perspective.

Regulation for hydroelectric production (i.e., hydropeaking) can impact aquatic species life cycle. During 2016–2017, radiotelemetry was used to track 22 Iberian barbels during a 1‐year cycle in a flow regulation scenario. Periodic samples of scales and biometric data were collected in a regulated (hydropeaking regime) and non‐regulated river within the same basin for comparison. Collected tracking, growth and condition data were compared with similar information for the same barbel population, obtained exactly on the same river stretch in a pre‐regulation period (2013–2014). Results on movement patterns of target species showed no effect of regulation on this biological component. However, potential intraspecific differences on migratory behaviour were found. We identified two behavioural profiles in each of the tagged fish groups: a ‘resident’ group that remains in upstream areas of the river during all the year round [maximum distance travel: mean (±SD) = 5.44 ± 5.36 km] and a ‘potamodromous’ group that travels long distances downstream after the reproductive season (20.24 ± 6.30 km).Flow regulation did not seem to affect the growth of the studied barbel populations; however, in terms of condition, differences between the pre‐ and post‐regulation periods were detected, with this parameter being higher for juvenile fish during the post‐regulation period. This study reveals important biological aspects of fish populations under short‐term flow regulation for hydroelectric purposes that should be considered in future monitoring programmes, when dam construction is planned, in order to develop more specific measures to improve habitat availability and quality for fish.