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Chinook spawning dune localities in British Columbia. The numbers correspond to localities in Table 2.
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... general, Chinook salmon spawning localities show a geographic pattern in which there are abundant spawners in a relatively few localities that produce much of the total run (Table 2; Figure 5), and localized small spawning aggregates at many sites. A few of the observed factors that contribute to good spawning grounds include an abundant sup- ply of gravel (channels are often coupled with a supply of allocthonous glacial gravels), typ- ically channel slopes that are less than 0.005 and active channel widths that range up to 500 m. ...
Citations
... The interaction between hydraulics and the substrate may be affected by the river morphology with parameters such as slope (Damgaard et al. 1997) or sinuosity (Donovan et al. 2021), but also by the presence of organisms modifying the current dynamics without any engineering action, i.e., macrophytes for example (Braun et al. 2012;Madsen et al. 2001). Organisms can also be engineers and alongside with processes such as burrowing of invertebrates Harvey et al. 2014), and fish nesting is a widespread biotic process (Gottesfeld et al. 2008;Barber 2013;Carpenter and McCreary 1985) that promotes riverbed substrate heterogeneity, especially in taxa such as salmonids, which move large volumes of sediment and alter local bed morphology (Gottesfeld et al. 2008). ...
... The interaction between hydraulics and the substrate may be affected by the river morphology with parameters such as slope (Damgaard et al. 1997) or sinuosity (Donovan et al. 2021), but also by the presence of organisms modifying the current dynamics without any engineering action, i.e., macrophytes for example (Braun et al. 2012;Madsen et al. 2001). Organisms can also be engineers and alongside with processes such as burrowing of invertebrates Harvey et al. 2014), and fish nesting is a widespread biotic process (Gottesfeld et al. 2008;Barber 2013;Carpenter and McCreary 1985) that promotes riverbed substrate heterogeneity, especially in taxa such as salmonids, which move large volumes of sediment and alter local bed morphology (Gottesfeld et al. 2008). ...
The sea lamprey (Petromyzon marinus L.) can be considered an ecosystem engineer, as it can substantially modify the river beds where it spawns. Sea lampreys dig nests by removing large volumes of cobbles to create a pit, and leaving them in a mound downstream, thus altering local bed morphology. Previous studies showed that sea lamprey nest-building behaviour increases riverbed heterogeneity in depth and water velocity, which in turn promotes macroinvertebrate diversity. Based on that finding, our study aimed at assessing whether these changes promoted ecosystem functioning. We measured multiple ecosystem functions (biofilm accretion, phosphate and ammonium uptake, and litter breakdown) on the pit and the mound of 30 lamprey nests, as well as on 30 unmodified sites. In spite of the physical heterogeneity, all processes measured showed no differences among sites, pointing towards a complex relationship between physical heterogeneity, biodiversity, and ecosystem function.
... Fish nesting, especially in species such as salmonids, which move large volumes of sed-35 iment and alter local bed morphology, is a biotic process that can increase riverbed substrate 36 heterogeneity (Gottesfeld et al., 2008). For migratory species with high nest density in the 5.1. ...
... The interaction between hydraulics and the substrate may be affected by the river morphology with parameters such as slope (Damgaard et al., 1997) or sinuosity (Donovan et al., 2021), but also by the presence of organisms modifying the current dynamics without any engineering action, i.e. macrophytes for example (Braun et al., 2012;Madsen et al., 2001). Organisms can also be engineers and alongside with processes such as burrowing of invertebrates Harvey et al., 2014), fish nesting is a widespread biotic process (Gottesfeld et al., 2008;Barber, 2013;Carpenter and McCreary, 1985) that promotes riverbed substrate heterogeneity, especially in taxa such as salmonids, which move large volumes of sediment and alter local bed morphology (Gottesfeld et al., 2008). ...
... The interaction between hydraulics and the substrate may be affected by the river morphology with parameters such as slope (Damgaard et al., 1997) or sinuosity (Donovan et al., 2021), but also by the presence of organisms modifying the current dynamics without any engineering action, i.e. macrophytes for example (Braun et al., 2012;Madsen et al., 2001). Organisms can also be engineers and alongside with processes such as burrowing of invertebrates Harvey et al., 2014), fish nesting is a widespread biotic process (Gottesfeld et al., 2008;Barber, 2013;Carpenter and McCreary, 1985) that promotes riverbed substrate heterogeneity, especially in taxa such as salmonids, which move large volumes of sediment and alter local bed morphology (Gottesfeld et al., 2008). ...
Nests are widespread in the animal world and aim to protect the young from predation and adverse environmental conditions while being a privileged place to assess sexual selection. These nests, modifications of the habitat in which they are built, influence the environmental conditions and likely affect the communities and
ecological processes. Among the nesting species, the sea lamprey (Petromyzon marinus L.) is an anadromous, semelparous migratory fish, whose nests consist of a mound of coarse elements downstream a pit with a fine substrate. The thesis firstly describes the reproductive behaviour of the sea lamprey by studying the link between the nests and the individuals that built them. A Capture-Mark-Recapture protocol showed that males and females visited up to 10 and 7 nests respectively, and that nests could be built by either pairs or groups of up to 5 individuals, resulting in a clearly polygynandrous mating system. Data obtained during this individual monitoring was used to set up a model providing a population size estimate via a simple nest count, a model that can be easily adapted to other populations and used via an online application. Intrasexual competition and cooperative nest building, as well as the existence of potential alternative reproductive tactics, were monitored at the scale of a nest and of an entire spawning site. Video monitoring within nests showed equal individual contributions to both nest building and mating, although aggressions perpetrated by some males suggested a hierarchy. Experimental injection of eggs into recently built nests indicated that the interaction between variables related to habitat choice (current velocity) and habitat modification (slope between the lower and upper points in the nest) affected egg retention in the nest, a major aspect of egg survival. Measurements of the maintenance of river lamprey (Lampetra fluviatilis L.) eggs in a controlled environment showed a significant role of substrate size. Finally, the link between the nest and its ecosystem was described through the study of the macroinvertebrate communities occupying the different zones and several ecosystem processes. The habitat heterogeneity created by sea lamprey generated biological heterogeneity, with an increased invertebrate diversity in the nest compared to control sites. However, nutrient retention, chlorophyll accretion and litter degradation were not affected. The general objective of this thesis is thus a better understanding of a species whose ecology and place in the ecosystem remain poorly understood, although threatened in its native range while being invasive where introduced, through the use of a characteristic structure of its life cycle: the nest.
... Fish nesting, especially in species such as salmonids, which move large volumes of sediment and alter local bed morphology, is a biotic process that can increase riverbed substrate heterogeneity [16]. For migratory species with high nest density in the spawning grounds, the ecological effects can be important and cascade to affect biological assemblages and ecosystem processes. ...
The habitat heterogeneity hypothesis states that increased habitat heterogeneity promotes species diversity through increased availability of ecological niches. We aimed at describing the local-scale (i.e. nest and adjacent substrate) effects of nests of the sea lamprey ( Petromyzon marinus L.) as ecosystem engineer on macroinvertebrate assemblages. We hypothesized that increased streambed physical heterogeneity caused by sea lamprey spawning would modify invertebrate assemblages and specific biologic traits and promote reach-scale diversity. We sampled thirty lamprey nests of the Nive River, a river of the south western France with a length of 79.3 km and tributary of the Adour River, in three zones: the unmodified riverbed (upstream) and zones corresponding to the nest: the area excavated (pit) and the downstream accumulation of pebbles and cobbles (mound). The increased habitat heterogeneity created by lamprey was accompanied by biological heterogeneity with a reduced density of invertebrates (3777 ± 1332 individuals per m ² in upstream, 2649 ± 1386 individuals per m ² in pit and 3833 ± 1052 individuals per m ² in mound) and number of taxa (23.5 ± 3.9 taxa for upstream, 18.6 ± 3.9 taxa in pit and 21.2 ± 4.5 taxa for mound) in the pit compared to other zones. However the overall taxa diversity in nest increased with 82 ± 14 taxa compared to the 69 ± 8 taxa estimated in upstream zone. Diversity indices were consistent with the previous results indicating a loss of α diversity in pit but a higher β diversity between a pit and a mound than between two upstream zones, especially considering Morisita index accounting for taxa abundance. Trait analysis showed high functional diversity within zones with a reduced proportion of collectors, scrapers, shredders, litter/mud preference and small invertebrates in mound, while the proportion of “slabs, blocks, stones and pebbles” preference and largest invertebrates increased. Pit presented the opposite trend, while upstream had globally intermediate trait proportions. Our results highlight important effects on species and functional diversity due to habitat heterogeneity created by a nest-building species, what can ultimately influence food webs and nutrient processes in river ecosystems.
... ecosystems (Holtgrieve and Schindler 2011). Bioturbation by salmon can mitigate fine sedimentation of streambeds, which suggests an active role for salmon in restoring fish habitat in streams (Gottesfeld et al., 2008;Holtgrieve and Schindler, 2011;Buxton, 2018). In European rivers, it was projected that the enhancement of fish stocks would reduce biological congestion and boost oxygen availability in aquatic organisms via top-down managing periphyton through benthic grazing and increased bioturbation (Gerke et al., 2021). ...
Habitat alterations and fragmentation caused by anthropogenic modifications of the riverine landscape have affected fish biodiversity by reducing the number of fish species. Fish are a major element of the aquatic environment, and they play an important role in maintaining ecosystem resilience. However, an incomplete understanding of links between river ecosystem functions and processes with fisheries is one of the major reasons for the alarming rate of decline of fish species. Recognizing the ecosystem services generated by fish populations is essential and is one step toward comprehensive, ecosystem-based management of riverine fisheries. Therefore, this paper is motivated by the need to explore the dimensions of fisheries as an ecosystem service. The data was collected from primary field observations and checklist-based key informant interviews at the seventeen fishing sites selected across an 800 km river stretch of the river. In addition, two focused group discussions with fishers at two sampling sites were held to provide first-hand knowledge of ecosystem services generated by fisheries. At first, the role of fisheries in generating ecosystem services for riverine ecosystem functioning and human demands is outlined using the Millennium Ecosystem Assessment approach. Then, the findings of a survey carried out from the headwaters to the delta of the Cauvery river are presented detailing the fisheries provisioning services, livelihoods, and other ecosystem services. The findings showed that the provisioning and cultural services are highly represented among the four categories of ecosystem services identified by the Millennium Ecosystem Assessment. However, in the literature reviewed, supporting, and regulating services are not well-represented. Based on these findings, the applicability of the ecosystem service concept can be elaborated to inform researchers and policymakers to enhance conservation efforts for fisheries.
... An assessment of spawning numbers in the Río Toltén watershed in Chile estimated that over 12,000 adult Chinook returned to this watershed between 2014 and 2015 (Gomez-Uchida, 2014). These numbers are comparable to Chinook populations in British Columbia, where the annual spawner abundance in individual populations generally does not exceed a few tens of thousands (Gottesfeld et al., 2008) and is often less than 1000 (Healey, 1982). Without the other, more abundant species of Pacific salmon, the effects of salmon in Patagonia will be less pervasive than in North America. ...
In their native range, Pacific salmon (Oncorhynchus spp.) have strong interactions with a multitude of species due to the annual pulse of marine‐derived nutrients that they deliver to streams and forests when they spawn and die. Over the past few decades, Chinook salmon (Oncorhynchus tshawytscha) has established non‐native populations throughout the Patagonia region of southern South America. Here, we provide the first assessment of the pathways through which salmon‐derived nutrients enter stream and forest food webs in Patagonia by surveying multiple streams in southern Chile to identify invertebrate and vertebrate consumers of salmon carcasses and summarizing all documented trophic interactions of Chinook salmon in Patagonia. Blowflies (Calliphoridae) were the dominant colonizer of carcasses in the riparian zone, and midge flies (Chironomidae) were the most common invertebrate on submerged carcasses. Camera trap monitoring in the riparian zone revealed consumption of carcasses or carcass‐associated invertebrates by the insectivorous passerine bird “chucao” (Scelorchilis rubecula), small rodents (black rat Rattus rattus, house mouse Mus musculus, and/or colilargo Oligoryzomys longicaudatus), the South American fox “culpeo” (Lycalopex culpaeus), and the invasive American mink (Neovison vison). A mink was filmed transferring a carcass from stream to streambank, indicating that vertebrate scavenging likely increases the degree to which marine‐derived nutrients enter terrestrial food webs. The native taxa that consume salmon are closely related to species that benefit from salmon consumption in North America, suggesting that the pathways of salmon nutrient incorporation in North American food webs have functionally re‐emerged in South America. Similarly, non‐native trout (Oncorhynchus mykiss and Salmo trutta) and mink consume salmon in Patagonia, and their eco‐evolutionary history of coexistence with salmon could mean that they are preadapted for salmon consumption and could thus be key beneficiaries of this invasion. Expanded monitoring of the abundance and impacts of salmon will be vital for understanding how these novel inputs of marine‐derived nutrients alter Patagonian food webs.
... Cyprinids, for example, are known to feed on sediment macrofauna as snails and chironomids and determine particles resuspension and nutrient mobilization in the water column [15]. Egg hiders like salmonids or lampreys, during the gravel nest digging, may significantly affect bottom properties [4,16,17]. Having very close sympatric distribution in rivers and streams of the Northern Hemisphere, salmonids and lampreys with their coarse-substrate bioturbation may produce profound ecological effects on their reproduction conditions [18] and on the stream ecosystems [4,16]. ...
Lampreys spend their larval stage within fine sand fluvial sediments, where they burrow and act as filter feeders. Lamprey larvae (ammocoetes) can significantly affect benthic-pelagic coupling and nutrient cycling in rivers, due to high densities. However, their bioturbation, feeding and excretion activities are still poorly explored. These aspects were investigated by means of laboratory incubations of intact sediments added with ammocoetes and of animals alone. Oxygen respiration, nutrient fluxes and excretion rates were determined. Individual ammocoete incubations suggested that biomass-specific oxygen consumption and ammonium, reactive phosphorus and silica excretion were size-dependent, and greater in small compared to large individuals. The comparison of ammocoetes metabolic rates with rates measured in intact sediments revealed that ammocoetes activity decreases significantly when they are burrowed in sediments. Furthermore, results suggest that a major fraction of ammonium excreted by ammocoetes was assimilated by benthic microbes or microalgae to overcome in situ N-limitation. Alternatively, part of the excreted ammonium was oxidized and denitrified within sediments, as nitrate uptake rather increased along with ammocoetes density. Ammocoetes excreted reactive phosphorus and silica but such production was not apparent in bioturbated sediments, likely due to microbial or microalgal uptake or to immobilization in sediments.
... Chinook are the least abundant species of Pacific salmon in North America and require the largest streams and substrate sizes for spawning habitat (Gottesfeld et al., 2008;Kondolf &Wolman, 1993). Larger substrates are harder to dislodge from the streambed and are therefore less prone to disturbance during salmon spawning (Holtgrieve et al., 2010;Janetski et al., 2009Janetski et al., , 2014. ...
... For example, low densities of spawning Chinook salmon (<0.001 spawners/m 2 ) caused a 46% increase in the gross primary production of three streams in Washington, U.S.A. (Benjamin et al., 2016), whereas moderate densities of spawning sockeye (Oncorhynchus nerka) salmon (>0.6 spawners/m 2 ) caused a 72% reduction in gross primary production in three streams in Alaska (Holtgrieve & Schindler, 2011). Although Chinook can have dramatic disturbance effects through the creation of spawning dunes in the streambed (Gottesfeld et al., 2008), this behaviour is observed only in the largest rivers in which they spawn and has not been reported in Patagonia, suggesting that they could be more likely to have a subsidy effect in their South American range. ...
The cover image is based on the Original Article Non‐native Chinook salmon add nutrient subsidies and functional novelty to Patagonian streams, by Nicolas J. Muñoz et al., https://doi.org/10.1111/fwb.13655.
... Chinook are the least abundant species of Pacific salmon in North America and require the largest streams and substrate sizes for spawning habitat (Gottesfeld et al., 2008;Kondolf &Wolman, 1993). Larger substrates are harder to dislodge from the streambed and are therefore less prone to disturbance during salmon spawning (Holtgrieve et al., 2010;Janetski et al., 2009Janetski et al., , 2014. ...
... For example, low densities of spawning Chinook salmon (<0.001 spawners/m 2 ) caused a 46% increase in the gross primary production of three streams in Washington, U.S.A. (Benjamin et al., 2016), whereas moderate densities of spawning sockeye (Oncorhynchus nerka) salmon (>0.6 spawners/m 2 ) caused a 72% reduction in gross primary production in three streams in Alaska (Holtgrieve & Schindler, 2011). Although Chinook can have dramatic disturbance effects through the creation of spawning dunes in the streambed (Gottesfeld et al., 2008), this behaviour is observed only in the largest rivers in which they spawn and has not been reported in Patagonia, suggesting that they could be more likely to have a subsidy effect in their South American range. ...
1. The impacts of non-native species are hypothesised to be proportional to the functional distinctiveness of invaders in their invaded ecosystems. Throughout the Patagonia region of southern South America, Chinook salmon (Oncorhynchus tshawytscha) have recently established non-native populations, and their anadromous, semelparous life cycle could be functionally unique such that marine-derived nutrients are delivered to streams which have historically lacked such a resource linkage with the ocean.
2. We tested the hypothesis that salmon subsidise biofilm-associated algae in streams throughout the Aysén province of southern Chile. Using spatial and temporal variation in the presence of salmon among multiple streams and across two spawning seasons, we found strong evidence of salmon-subsidised algae in three out of four streams examined that have spawning salmon populations.
3. The biofilm of subsidised streams had enriched stable isotopic ratios of nitrogen and carbon, indicating that marine-derived nutrients were incorporated by biofilms. This nutrient uptake translated into increased algal biomass and percent of total biofilm biomass composed of algae, indicating that the incorporation of marine-derived nutrients stimulated autotrophic production of biomass.
4. In one stream, the incorporation of marine-derived nutrients by biofilm occurred in only one of the two studied spawning seasons. Incorporation occurred in a year with low flows of water throughout salmon spawning (4.59 m3/s) and did not occur in a year with much higher flows (41.6 m3/s), suggesting that inter-annual variation in discharge can mediate the subsidising effect of salmon.
5. These results indicate that Chinook salmon have bridged the historical gap between productive marine ecosystems and nutrient-poor stream ecosystems in Patagonia. Anadromous salmon can be a significant source of nutrients in nutrient-limited catchments, and their ongoing expansion in southern South America is likely to entail ecological impacts in stream and riparian food webs.
KEYWORDS: eutrophication, invasive species, Oncorhynchus, periphyton, stable isotopes
... Sediment movement in downstream regions and alteration in streambed morphology due to salmon bioturbation has been well documented (Gottesfeld et al., 2004;Peterson and Quinn, 1996). Fish can potentially cause sediment movement during both, spawning and post-spawning periods (Crisp and Carling, 1989;Gottesfeld et al., 2008;Gottesfeld et al., 2004). For instance, during the spawning period, high densities of fish are found in regions which have good supply of food and nutrients. ...
... transport (Albers & Petticrew, 2013;Buxton et al., 2015;Field-Dodgson, 1987;Gottesfeld et al., 2008;Hassan et al., 2008Hassan et al., , 2015Kondolf et al., 1993;Macdonald et al., 2010;Montgomery et al., 1996;Moore, 2006;Moore et al., 2004;Peterson & Foote, 2000). We speculate that foraging may be equally, if not more, important as a zoogeomorphic mechanism in UK rivers. ...
Flume studies have demonstrated that foraging by fish can modify the structure and topography of gravel substrates, thereby increasing particle entrainment probabilities and the amount of sediment mobilized during subsequent experimental high flows. However, the zoogeomorphic impact of benthic foraging has not previously been investigated in the field. This paper reports field experiments that examined the nature and extent of disturbance of riverbed gravels by foraging fish, predominately Cyprinids, at patch, riffle, and reach scales and complementary ex situ experiments of the impacts on bed stability. At patch scale, benthic feeding fish displaced particle sizes ≤90 mm in diameter, increased bed surface microtopography and grain protrusion, and loosened surface structures. Although enhanced mobility was expected from these structural changes, foraging also caused localized coarsening of sediments, and the ex situ experiments recorded significantly reduced grain entrainment, bedload flux, and total transported mass from foraged patches. Foraging disturbed bed materials at all 12 riffles in the study reach and, on average, disturbed 26.1% of riffle area per 24 h feeding period. These findings demonstrate for the first time that foraging fish, which are widespread and feed perennially, can act as zoogeomorphic agents in rivers, affecting grain-size distributions and bed material structure, with potential implications for bed stability and bedload transport at reach and river scales. Whether fish increase or reduce bed mobility is probably dependent on a host of factors, including the net effects of both structural disturbance and biogenic particle sorting, as these affect entrainment stresses under subsequent competent flows.
