A Review of Habitat Connectivity Research for Pacific Salmon in Marine, Estuary, and Freshwater Environments

Abstract

Research Impact Statement: Science supporting Pacific salmon habitat connectivity is dominated by freshwater studies with limited marine and estuary work that is also critical for effective conservation planning.ABSTRACT: Long-term conservation planning for diadromous fishes would benefit from a better understanding of both the role of connectivity among environments and habitat variability in the expression of life-history diversity. Most of the scientific knowledge on habitat fragmentation and connectivity has been developed in terrestrial systems in the discipline of landscape ecology. Research on habitat connectivity in aquatic systems (e.g., salmonid research that spans the spectrum of habitats from freshwater to the sea) is uncommon and largely focused on barriers to fish passage. Here, we present a review of the literature characterizing current research patterns on habitat connectivity within and among environments for Pacific salmon. We found this topic is still incipient: the literature is dominated by studies of freshwaters, with few articles focusing on habitat needs in estuary and marine systems. Pan-environment studies are rare, pointing to a gap in our understanding of complex habitat relationships that might be significant in the development of long-term conservation and restoration plans for Pacific salmon, particularly in light of the potential impact of climate change.

Research Progress on Habitat Connectivity in Temperate Waters

“…Flitcroft proposed habitat patterns for freshwater, estuarine, and marine environments for Pacific salmon (Oncorhynchus spp.) that are important for population recovery and long-term conservation [38]. Quevedo found that the degree of niche differentiation in Eurasian perch, which has a broad diet in different habitats, may have a significant effect on habitat connectivity and trophic dynamics, suggesting that specific individuals can link spatially separated nutrient and energy flows to create new heterogeneity to restructure food webs [39][40][41].…”

Featured Collection Introduction: The Emerging Science of Aquatic System Connectivity I

“…A third paper in this featured collection by Flitcroft et al. () provides a review on habitat fragmentation and connectivity in aquatic systems. Using Pacific salmon as a case study, Flitcroft et al.…”

“…Using Pacific salmon as a case study, Flitcroft et al. 's () review highlights the need for “pan‐environment studies” that take into account connectivity between upstream, estuarine, and marine habitats — elements necessary for complex life cycles of many species.…”

Habitat loss due to dam development may affect the distribution of marine‐associated fishes in Gabon, Africa

“…Developing large‐scale freshwater conservation strategies requires understanding patterns of connectivity between marine, estuarine, and freshwater ecosystems (Flitcroft et al. ), but few studies have incorporated the entire range of habitats required by marine‐associated fish species in tropical river systems.…”

“…Migratory fishes, including marineassociated fishes that rely on multiple distinct habitats, are particularly susceptible to dam construction (Aleem 1972, Drinkwater and Frank 1994, Stanford and Ward 2001, Rowell et al 2008, Stone 2011. Developing large-scale freshwater conservation strategies requires understanding patterns of connectivity between marine, estuarine, and freshwater ecosystems (Flitcroft et al 2019), but few studies have incorporated the entire range of habitats required by marineassociated fish species in tropical river systems.…”