In regulated rivers, hydropeaking may create abrupt sub-daily changes in discharge that can rapidly alter fish habitat. Although hydropeaking impacts on juvenile salmonids have been widely studied, short-term effects on foraging by early life stages remain poorly documented. We used a laboratory flume experiment to test how a downramping flow regime and substrate heterogeneity affect the foraging performance of brown trout (Salmo trutta) fry. We exposed fry to four treatments, combining two flow conditions (stable vs. downramping) and two substrates (gravel vs. gravel with cobbles). We quantified individual total prey intake, assessed from stomach contents, and drift-feeding activity from video analyses. Our results showed that the flow treatment had no detectable effect on total prey intake, indicating that both stable and rapid flow reductions did not disrupt short-term feeding under an adequate food supply. The number of drift-feeding attempts was similar across all treatments. In contrast, the presence of cobbles increased total prey intake, suggesting that structural complexity enhanced intake by providing hydraulic refuges and additional feeding opportunities. Prey intake showed a general size-dependent pattern, with larger fry consuming more prey. Our findings indicate that adding or maintaining fine-scale substrate complexity is a potent enhancer of fry feeding and should be considered as a restoration measure for habitat mitigation in hydropeaking rivers. 

In regulated rivers, hydropeaking operations have been identified as having significant effects on spawning, growth, reproduction, and behavior of juvenile salmonids. Such effects may reduce survival rates and population viability, but such long-term studies are challenging. Due to the inherent difficulties of conducting large-scale replicated studies in such regulated rivers in situ, river managers require new tools to assess how mitigation measures may affect fish populations. In this study, we used inSALMO 7.3-SD, an individual-based model developed for hydropeaking studies, to investigate the effects of three levels of minimum baseflows (9, 12 and 15 m3/s) and spawning gravel augmentation on the size and number of Atlantic salmon (Salmo salar) and brown trout (S. trutta) outmigrants in the hydropeaking-regulated River Gullspång, Sweden. Our results show that under hydropeaking conditions, higher minimum flows increased outmigrant size, they simultaneously reduced outmigrant numbers, affecting age-1 trout and age-2 individuals of both species. In contrast, gravel augmentation did not affect outmigrant size but generally increased outmigrant production, mainly benefiting age-1 salmon and age-2 trout, although this effect diminished at higher base flow levels. We identified poor body condition and fish predation of juveniles as the primary mortality sources driving the effects on outmigrant production. Our results indicate that the spatial distribution of juveniles was affected by gravel addition and that this effect in turn led to altered mortality rates. Our findings underscore the complex interplay between flow management, habitat modifications, and species-specific behaviors. Also, they highlight the need to carefully balance operational and morphological restoration measures to optimize habitat quality and support effective conservation of salmonids in hydropeaking-regulated rivers. 

Effective and locally supported river restoration requires attention to the social dimensions of rivers. This paper examines local perceptions of hydropower and restoration in the river R & ouml;nne & aring;, an early case under Sweden's National Plan for Modern Environmental Conditions for Hydropower. A mixed-methods approach, including a questionnaire and qualitative interviews, explores how inhabitants relate to their river and view the removal of three low-production dams, offering one of the most detailed assessments of stakeholder values in a Swedish hydropower river. The findings reveal important tensions between energy production and ecological restoration: While hydropower retains cultural legitimacy, support declines when ecological costs outweigh energy benefits. The river holds strong recreational, cultural, and symbolic meanings, embedding dam removals in broader sociocultural contexts rather than solely technical or ecological. These findings highlight the importance of participatory efforts and governance that align ecological goals with the diverse ways people relate to rivers.

The consideration of local knowledge in assessments and governance of biodiversity and ecosystems is a vital challenge for a just and sustainable future. This requires in-depth consideration of the intricate ways people know, engage with and are affected by natural environments. However, the concept of local knowledge is fluid, and several interpretations are in use, which can complicate constructive engagement. This paper aims to provide a descriptive overview and analytical framework for diverse conceptualisations of local knowledge in biodiversity and ecosystem governance. We focus on two objectives: (i) to describe and critically examine conceptualisations of local knowledge in the scientific and grey literature; and (ii) to develop a set of characteristics that can be used to identify local knowledge. Rather than seeking a single definition, we examine a range of academic interpretations, while extending the discussion to knowledge systems and holders in the nonIndigenous Global North. We analyse differences and similarities between local knowledge and related concepts such as Traditional Ecological Knowledge, Indigenous and Local Knowledge, lay knowledge, scientific knowledge and policy-oriented understandings of local knowledge. We propose a flexible framework to identify and characterise local knowledge in research. The framework combines questions about researchers' motivations and methodological choices with dimensions concerning knowledge holders, locus of knowledge, spatial and temporal dimensions, and modes of knowledge transmission. We emphasise the importance of critically engaging with the concept of knowledge itself to recognise the complementarity of diverse knowledge systems and support more reflexive approaches to local knowledge in biodiversity and ecosystem governance.

Hydropeaking may result in behavioral responses in riverine organisms that experience rapid flow fluctuations. In stream fish, the balance between energy spent on swimming and foraging vs. food intake affects fitness, a balance strongly influenced by flow conditions. This study investigates the effects of rapid flow fluctuations on the foraging success, group cohesion (nearest neighbor distance) and microhabitat segregation of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) parr (45-55 mm) in both sympatric and allopatric groups in a controlled laboratory stream environment. Our results indicate that fluctuating flow does not significantly influence the foraging success in either species, regardless of group composition (sympatry or allopatry). We found that group composition, rather than flow fluctuation, significantly influenced group cohesion. Salmon exhibited shorter nearest neighbor distances than trout did in allopatry, but not in sympatry. In terms of microhabitat selection, salmon consistently held position closer to the substrate than trout, regardless of group composition, suggesting selective segregation as the main mechanism driving microhabitat selection. Trout, on the other hand, held position higher above the substrate in allopatry but used a wider range of positions when in sympatry with salmon, highlighting interactive segregation as a possible mechanism driving microhabitat use, which underscores the importance of fish community in shaping patterns of habitat use. Our findings suggest that hydropeaking may not strongly impair the foraging ability and sociability of salmon and trout parr. Additionally, we shed light on the mechanisms influencing microhabitat selection of salmon and trout parr in rivers with a hydropeaking flow regime. One possible application of our results is as inputs for individual-based models currently being developed for understanding the effects of hydropeaking on stream salmonid populations.

A workflow for developing a cost- and time-efficient, single nucleotide polymorphism (SNP)-based assay for species and hybrid identification is described. In a reference set (n = 46), the developed assay identified individuals of two closely related species, the Atlantic salmon (Salmo salar L., n = 23) and brown trout (Salmo trutta, n = 23), with 100% accuracy. Furthermore, species and hybrid identification using field-collected embryos had 98.1% concordance (155/158) to more expensive and time-consuming methods that utilized multiple SNP markers. The method can be integrated into management and conservation plans to quantify species' spawning distribution and hybridization rates.

Earth is faced with an anthropogenic biodiversity crisis. The Sixth Mass Extinction is the first mass extinction to be driven by a single species, Homo sapiens. In this brief essay, I briefly recount salmonid biodiversity, concluding that a vast portion of historic biodiversity has already been lost, mirroring global biodiversity loss in general. I then recount the concepts of instrumental and intrinsic value, anthropocentrism and ecocentrism, in relation to biodiversity conservation. I conclude that intrinsic natural value is an incontrovertible aspect of biodiversity conservation, and that ecocentrism is one key aspect of a truly sustainable transformation of the relationship among human and nonhuman beings. A sound rationale for protecting the world’s remaining salmonid biodiversity must rest in part upon the recognition of, and respect for, intrinsic natural value.

We highlight the need for ecological justice and ecological ethics to go hand in hand with social justice in conservation science. We focus on the importance of ecocentric (non-anthropocentric) worldviews for advancing both social and ecological justice. While acknowledging the need to “decolonize” conservation, we question whether conservation a whole may be justifiably termed “colonial”; noting that colonialism in the name of profit and political power has long been a main driver of both human rights abuses and biodiversity loss. Moreover, modern conservation science explicitly strives for social justice and equity while protecting biological diversity and thus ought not to be conflated with colonialism’s long and unjust history. We suggest that efforts to portray modern conservation science as patriarchal, racist, and colonial are shortsighted, disregarding longstanding efforts by conservationists to reconcile social and ecological values. Such critiques may adopt a patronizing approach to Indigenous and local peoples, portraying them as idealized guardians. Such views may obscure the complex socio-economic conditions that leave indigenous and local communities vulnerable to resource exploitation; these factors must be understood if these groups are to fulfil their vital role as conservation allies. We conclude that the conservation community should shift focus toward targeting the main political actors and economic structures that oppress both humans and non-humans alike. A more nuanced appreciation of the shared history of colonialism and conservation may illuminate how social and ecological values converge in the mission of sustaining the ecological life support system on which every human and non-human being depends. 

Multiple anthropogenic forces have pushed river ecosystems into undesirable states with no clear understanding of how they shouldbe best managed. The advancement of riverine fish habitat models intended to provide management insights has slowed. Investigations into theoretical and empirical gaps to define habitat more comprehensively across different scales and ecological organizationsare crucial in managing the freshwater biodiversity crisis. We introduce the concept of novel riverscapes to reconcile anthropogenicforcing, fish habitat, limitations of current fish habitat models, and opportunities for new models. We outline three priority data-drivenopportunities that incorporate the novel riverscape concept: fish movement, river behavior, and drivers of novelty that all are integratedinto a scale-based framework to guide the development of new models. Last, we present a case study showing how researchers, modeldevelopers, and practitioners can work collaboratively to implement the novel riverscape concept.

We use the case study of coho salmon and steelhead trout to discuss the coexistence of two similar stream salmonid species. The question of coexistence between these two species dates back to the early 1960s, making it a good example of the application of ecological theory to explain patterns observed in nature. Explanations for habitat selection and segregation between coho salmon and steelhead trout have included the mechanisms proposed by Nilsson (The biological basis of freshwater fish production. John Wiley and Sons, New York, 1967), interactive segregation and selective segregation. Through examples of laboratory and field studies of coho salmon and steelhead trout in Southeast Alaska, we suggest that habitat selection appears to be largely selective, but interactive segregation may become important during times of resource limitation. Despite a half-century of scientific inquiry into the coho-steelhead coexistence question, there is still much to be learned about habitat selection of these species; given the precarious status of many populations of coho salmon and steelhead trout within their native range, efforts to understand their ecological requirements are warranted.