Distribution Of Salmon Research Articles

Adapting management of Pacific salmon to a warming and more crowded ocean

Abstract The North Pacific Ocean is warming and overall Pacific salmon abundance is higher now than at any other time in the past century. This increase in abundance is in large part due to warming-related changes in marine ecosystems at northern latitudes that primarily benefit pink salmon, and industrial-scale hatchery production to support commercial fisheries. A large body of evidence indicates that increasing and more variable ocean temperatures, as well as competition among salmon at sea, are associated with shifts in salmon productivity, body size, and age at maturation. However, these relationships vary by species, location, and time, resulting in increased harvest opportunities in some regions and exacerbated conservation concerns in others. The weight-of-evidence suggests North Pacific salmon nations should, as a minimum, limit further increases in hatchery salmon production until there is a better scientific understanding of hatchery and wild salmon distribution at sea, how they interact, and how the consequences of these interactions are influenced by broader climate and ecosystem conditions. Coordinated research to overcome knowledge gaps and develop strategies to reduce unintended interactions between hatchery and wild salmon could be funded (in part) by a tax placed on industrial-scale hatchery salmon releases. A tax would formalize recognition that there are finite prey resources to support salmon in the ocean and that both prey and wild salmon represent a “common property” whose use should not be without cost to those that seek to benefit from them. We highlight additional approaches salmon nations can take to adapt to changing conditions and suggest that improved communication and collaboration among North Pacific salmon research and management agencies will be key to balancing the benefits and risks of a warming and more crowded ocean.

Biological and environmental covariates of juvenile sockeye salmon distribution and abundance in the southeastern Bering Sea, 2002-2018.

Climate change is altering the distribution and abundance of marine species, especially in Arctic and sub-Arctic regions. In the eastern Bering Sea, home of the world's largest run of sockeye salmon (Oncorhynchus nerka), juvenile sockeye salmon abundance has increased and their migration path shifted north with warming, 2002-2018. The reasons for these changes are poorly understood. For these sockeye salmon, we quantify environmental and biological covariate effects within spatio-temporal species distribution models. Spatio-temporally, with respect to juvenile sockeye salmon densities: (1) sea surface temperature had a nonlinear effect, (2) large copepod, Calanus, a minor prey item, had no effect, (3) age-0 pollock (Gadus chalcogrammus), a major prey item during warm years, had a positive linear effect, and (4) juvenile pink salmon (O. gorbuscha) had a positive linear effect. Temporally, annual biomass of juvenile sockeye salmon was nonlinearly related to sea temperature and positively related to age-0 pollock and juvenile pink salmon abundance. Results indicate that sockeye salmon distributed with and increased in abundance with increases in prey, and reached a threshold for optimal temperatures in the eastern Bering Sea. Changes in population dynamics and distribution of sockeye salmon in response to environmental variability have potential implications for projecting specific future food securities and management of fisheries in Arctic waters.

Opening the black box: New insights into the role of temperature in the marine distributions of Pacific salmon

AbstractPacific salmon (Oncorhynchus spp.) spend much of their life near the ocean surface where climatic and oceanographic conditions affect their habitat and survival. Despite decades of study, critical knowledge gaps persist regarding their ecology and distributions. Consequently, it has been difficult to assess how environmental conditions influence the high‐seas distribution and habitat use of these culturally and socioeconomically important fishes, presenting challenges to fisheries managers trying to evaluate how climate change and fishing activities may impact salmon populations. We used a recently compiled, comprehensive database of historical coastal and high‐seas salmon survey data (1953–2022) in the North Pacific to fit species distribution models that (1) characterize the marine spatial distribution of six species of Oncorhynchus, (2) evaluate species‐specific temperature preferences, and (3) investigate how species' temperature preferences influence distribution. Sea surface temperature, along with seasonal migrations associated with spawning and feeding, significantly affects the distribution of all species, where the warm limits of estimated preferred thermal ranges were more similar than the cold limits. Furthermore, the distributions of some species appear more responsive to temperature than others and recently observed warm conditions have likely impacted realized ranges. These models have expanded our understanding of salmon ocean distributions and thermal niches by providing a unique window into this often unobserved but important part of the life cycle. They also serve as a baseline for future investigations into the mechanisms influencing salmon spatial ecology, responses to climate change, and vulnerability to harvest across the North Pacific.

Marine biophysical conditions influence the vertical and horizontal distribution of sub-adult Chinook salmon in the nearshore marine waters of Washington State

Marine biophysical conditions influence the vertical and horizontal distribution of sub-adult Chinook salmon in the nearshore marine waters of Washington State

Atlantic salmon (Salmo salar) distribution and vertical size-stratification in a commercial sea cage: A case study

Biomass and size estimates of fish are most valuable information to assure optimal management in Norwegian Atlantic salmon production. Such estimates are largely based on models and small samples of few individuals, and improvements are required for better representativity. Advances in machine learning triggered fast development of automated size estimation using stereovision cameras. These measurement systems can result in precise measurements of individual fish. Nevertheless, fish behavior needs to be considered for a proper description of the true mean and variation of fish sizes of cage populations because salmon distribution is not homogeneous in sea cages. Most studies on salmon distribution were performed in relatively small sea cages and additional experiments at commercial scale are required to verify that previous findings are applicable under industrial conditions. In this case study, we monitored vertical and horizontal distributions of salmon in a commercial sea cage. Vertical size stratification was investigated using stereovision cameras, and salmon and growth-stunted fish abundances and swimming speed were measured using cameras recording simultaneously in 16 positions: four horizontal positions and four depths (1 m, 5–6 m, 9–11 m and 14–16 m), four times during one day. Our results suggest a heterogeneous vertical distribution with longer individuals found deeper in the sea cage at high abundance and swimming more slowly than smaller individuals, including growth-stunted fish, found in low abundance close to the surface. Cumulative mean fork-lengths per depth were compared to the estimated true mean fork-length for the whole population of the cage and results show that automatic biomass and size estimation based on a single depth likely results in biased size estimation for the cage population. On the contrary, horizontal distribution appeared homogeneous, and our data supports the assumption that fish were exhibiting a circular swimming pattern, as previously described in small sea cages and under slow current conditions. Our study adds data to currently still scarce knowledge about fish behavior and distribution at commercial scale and provides indications on the use of new technologies for biomass and size estimation. Further studies on longer timelines and different locations are necessary to further generalize behavioral models.

Reproduction, biometric patterns of pink salmon and effect of commercial fishery on the runs of the species on the south of the north-eastern coast of Sakhalin Island in 2021

Purpose: to present up-to-date data on the dynamics of the spawning run, reproduction conditions and biometric characteristics of pink salmon in three reference watercourses in the southern part of the north-eastern coast of Sakhalin Island, as well as analysis of impact of commercial fishing on the spawning run and distribution of spawners within spawning grounds. Methods: common methods of ichthyological research were applied to collect and process field data. Data were synthesized in MS Excel, analysis and visualization were carried out in MS Excel and Statistica. Scientific novelty: results of monitoring of pink salmon in the southern part of the north-eastern coast of Sakhalin are presented. Despite the intensive commercial fishery in this area, there are no other data on the dynamics of pink salmon runs, density of breeders on spawning grounds, and biometric characteristics of spawners, except for those presented in this paper. Result: data on the timing of spawning migration, distribution of pink salmon within spawning grounds and degree of occupation of spawning grounds, temporal structure of spawning run; bio-metric characteristics of pink salmon are presented. Assessment of the influence of commercial fishing on the dynamics of spawning run and distribution of pink salmon within spawning grounds is discussed. Practical relevance: the presented data is an integral part of information supply of fishery research of the most widespread species of Pacific salmon - pink salmon, which forms the basis of salmon fishery in the Sakhalin Region. Also, the presented data is applicable for preparation of scientifically-based recommendations for optimizing the fishing pressure.

Using human health disparities and salmon health to guide spatial prioritization of green stormwater infrastructure

Stormwater pollution is pervasive in urban environments and has negative consequences for both the people and ecosystems that occur within these regions. These pollutants cause mortality and other forms of harm in aquatic ecosystems. In the human landscape, stormwater pollution is detrimental to human health and unfairly impacts communities of color and people of lower socioeconomic status. While the sources of stormwater pollution are clear, the solutions can be costly and need to be placed intentionally to target benefits to both human and wildfire. Multi-objective planning is an important tool for being strategic about making decisions for prioritization to ensure that multiple benefits are achieved. We provide a case study regarding the consequences of multi-objective prioritization using both human health disparities and salmon distribution. We used a risk-assessment framework to evaluate human and salmon health goals on three different opportunities for stormwater mitigation to compare the outcomes from different management decisions. Our results indicated that using a dual objective prioritization that includes human health and equity in addition to salmon health provides very similar outcomes when compared to including just a single goal. Using a single objective can limit the ability of stormwater mitigation projects to provide co-benefits. Only limited trade-offs were found when incorporating equity and environmental justice into planning decisions that typically include only water quality or ecosystem health into the decision-making process. Our methods can provide a framework for practitioners to expand their scope of work and ensure that solutions are more equitable.

Distribution and straying of minijack Chinook Salmon released from a captive broodstock hatchery program

AbstractObjectiveProduction of Chinook Salmon Oncorhynchus tshawytscha in hatcheries can unintentionally produce large numbers of age‐1 males, termed "minijacks," which pose ecological and genetic risks to target and nontarget populations. We evaluated the postrelease distribution of minijacks produced in a hatchery captive broodstock program targeting the White River in the Columbia River basin between 2010 and 2015.MethodsFish were passive integrated transponder (PIT)‐tagged in the hatchery (n = 218,555), and databases were searched to determine movement behavior and final detections on fixed PIT tag antenna arrays during the year in which they were released.ResultTwo main movement behaviors were detected: (1) residuals, which moved solely within the subbasin of release; and (2) migrants, which moved downstream into the Columbia River and then reascended the Columbia River in the year of release. Minijacks that reascended fish ladders in the Columbia River were most often detected at Rock Island and Bonneville dams, the nearest and furthest detection locations downstream of the Wenatchee River. Minijacks were last detected in all locations where spring Chinook Salmon spawn in the Wenatchee River subbasin (seven tributaries and one main‐stem area) and also in the Entiat River (an adjacent watershed); minijacks in eight of the nine locations were considered strays. Estimates of minijacks that strayed outside of the White River were between 61% and 100% annually and were influenced by release location. Minijacks were also more abundant than males of all older ages in some of the tributaries during some years. In addition, they were detected in these tributaries during periods when anadromous adults migrate into spawning areas and when spring Chinook Salmon spawn.ConclusionThe large amount of minijack production and the spatial and temporal overlap could pose genetic and ecological risks to both target and nontarget populations and particularly high straying poses risks to the maintenance of between‐population genetic variability.

Observing the Arctic: A comparison of environmental DNA (eDNA) and electrofishing for monitoring Arctic char and Atlantic salmon

AbstractThe current knowledge about fish biodiversity and species distributions in Arctic freshwater systems is generally limited. This contrasts the clear urgency for more accurate biodiversity data to assess the effects of future ecosystem challenges such as climate change and other anthropogenic effects. Here we compare traditional electrofishing surveys with environmental DNA (eDNA) for monitoring species distribution of Atlantic salmon (Salmo salar) and Arctic char (Salvelinus alpinus) in the West Greenlandic sub‐Arctic river system of Kapisillit, which contains the only known population of Atlantic salmon in Greenland. Overall, electrofishing and eDNA surveys show high compatibility in regard to species detection and quantification, with Arctic char confirming a significant relationship between eDNA concentration and observed fish abundance. Both methods confirm a shift in species occurrence and relative species abundance through the river system. Specifically, salmon is restricted to the lower warmer sections of the river system while Arctic char is found throughout the system but dominates the upper parts. In total, the study supports eDNA as a promising tool for fish community assessment, which may serve a wide array of applications for Arctic freshwater monitoring. These applications include analyzing species occurrence and distribution of native and invasive species, as well as documenting potential shifts in relative species abundance as shown here. Given the ease of sampling and high sensitivity of the method, eDNA provides a powerful cost‐effective approach capable of detecting species in remote areas as well as corroborating fish community monitoring programs. This may especially be valuable for monitoring in the Arctic where logistic complications with sampling and high operational costs so far constrains routine monitoring.

Including environmental covariates clarifies the relationship between endangered Atlantic salmon (Salmo salar) abundance and environmental DNA

AbstractCollecting environmental DNA (eDNA) as a nonlethal sampling approach has been valuable in detecting the presence/absence of many imperiled taxa; however, its application to indicate species abundance poses many challenges. A deeper understanding of eDNA dynamics in aquatic systems is required to better interpret the substantial variability often associated with eDNA samples. Our sampling design took advantage of natural variation in juvenile Atlantic salmon (Salmo salar) distribution and abundance along 9 km of a single river in the Province of New Brunswick (Canada), covering different spatial and temporal scales to address the unknown seasonal impacts of environmental variables on the quantitative relationship between eDNA concentration and species abundance. First, we asked whether accounting for environmental variables strengthened the relationship between eDNA and salmon abundance by sampling eDNA during their spring seaward migration. Second, we asked how environmental variables affected eDNA dynamics during the summer as the parr abundance remained relatively constant. Spring eDNA samples were collected over a 6‐week period (12 times) near a rotary screw trap that captured approximately 18.6% of migrating smolts, whereas summer sampling occurred (i) at three distinct salmon habitats (9 times) and (ii) along the full 9 km (3 times). We modeled eDNA concentration as a product of fish abundance and environmental variables, demonstrating that (1) with inclusion of abundance and environmental covariates, eDNA was highly correlated with spring smolt abundance and (2) the relationships among environmental covariates and eDNA were affected by seasonal variation with relatively constant parr abundance in summer. Our findings underscore that with appropriate study design that accounts for seasonal environmental variation and life history phenology, eDNA salmon population assessments may have the potential to evaluate abundance fluctuations in spring and summer.

Environmental DNA survey of the Winter Salmonosphere in the Gulf of Alaska

AbstractPacific salmon (Oncorhynchus spp.) are a foundation species around the north Pacific, yet many wild populations have experienced steep declines over the last decades associated with decreased marine survival. Due to limited sampling, our understanding of the dynamic North Pacific Ocean ecosystem remains poor and factors impacting marine survival of salmon remain largely unknown, specifically in the winter when salmon face limited resources. Here, we present a late winter ecosystem‐wide environmental DNA (eDNA) survey performed in 2019 and 2020 in the Gulf of Alaska. Our eDNA data refines the ocean distribution and relative abundance of Pacific salmon, as well as their prey such as copepods. Vertical diurnal migrators like myctophids and squid that are prey and/or competitors of salmon and represent the bulk of the open ocean biomass in the Gulf of Alaska. We detected these species irrespective of time of day in the eDNA data, resolving the nighttime bias associated with trawl catches. Furthermore, eDNA uncovered cryptic predators of salmon such as salmon sharks (Lamna ditropis) and beaked whales (Ziphiidae) not evident from catch or observer data. Open‐ocean communities of the central Gulf of Alaska were characterized by low species richness in contrast to hotspots of biological activity associated with oceanographic features such as eddies and the continental shelf. Network analysis revealed the ecological interactions that salmon navigate in the open‐ocean ecosystem by identifying key prey species, competitors, and predators and revealed the negative impact of the northern sea nettle (Chrysaora melanaster) on salmon that was associated with a marine heatwave in 2019. Finally, we highlight the utility of eDNA for open ocean ecosystem research and provide recommendations for further surveys. This dataset, complementing traditional survey methods, illustrates the winter salmonosphere in the North Pacific Ocean at improved resolution and provides a baseline for future research.

Landscape characteristics influence projected growth rates of stream‐resident juvenile salmon in the face of climate change in the Kenai River watershed, south‐central Alaska

AbstractObjectiveClimate change is affecting the distribution and productivity of Pacific salmon throughout their range. At high latitudes, warmer temperatures have been associated with increased freshwater growth of juvenile salmon, but it is not clear how long this trend will continue before further warming leads to reduced growth. To explore the potential influence of climate warming on juvenile Chinook and Coho Salmon summer growth rates in southcentral Alaska, we coupled bioenergetics models with temperature sensitivity models for streams across the Kenai River watershed.MethodsWe measured diet (n = 772 stomachs) and growth (n = 3,791 weight/length values) under current conditions and used published air temperature projections to model growth for the 2030–2039 and 2060–2069 decades.ResultWe estimated direct effects of climate warming on juvenile growth (body mass at the end of May–September study period) will be primarily negative, ranging from +5.1% to −22.8% relative to a 2010–2019 baseline. Estimated effects depended on age cohort, feeding rate, and climate scenario. However, an extended growing season from warming could mitigate or offset predicted reductions in growth during midsummer.ConclusionOur results illustrate how diverse habitats are expected to produce variation in the magnitude of climate effects throughout juvenile salmon rearing environments.

Species‐specific patterns in spatio‐temporal dynamics of juvenile chum salmon and their zooplankton prey in Otsuchi Bay, Japan, revealed by simultaneous eDNA quantification of diverse taxa from the same water samples

AbstractTo understand the spatio‐temporal dynamics of juvenile chum salmon Oncorhynchus keta and their zooplankton prey, the neritic Pseudocalanus newmani, the oceanic Eucalanus bungii, and Themisto japonica, we developed species‐specific environmental DNA (eDNA) quantification methods. First, we confirmed that juvenile chum salmon collected in Otsuchi Bay preyed on the target zooplankton by the stomach contents analyses using the developed assays. Size‐fraction analyses of the water collected in the bay showed that P. newmani and E. bungii DNA were derived mostly from nauplii and early copepodids. We then investigated the distribution and abundance of zooplankton and juvenile chum salmon in Otsuchi Bay using eDNA analyses of the same water samples collected from January to June in 2018 and 2019. Chum salmon DNA was found in the bay from the end of January to mid‐June. P. newmani DNA appeared across the bay throughout the season and were most abundant from February to May, while the other two species DNA were only found in spots, in lower quantities, from March to May. The timings that the zooplankton DNA quantities became greater were corresponded well to that of the Oyashio water intrusion into the bay. In addition, the environmental data indicates that P. newmani was possibly transported also by the Coastal Oyashio water in 2019. The present study successfully revealed species‐specific patterns in the dynamics of zooplankton and chum salmon, reflecting their ecological characteristics and oceanographic conditions, and showed the effectiveness of simultaneous eDNA quantifications for diverse taxa from the same water samples.

High temperature events shape the broadscale distribution of juvenile Atlantic salmon (Salmo salar)

Abstract Summer water temperatures within many temperate rivers regularly surpass the incipient lethal temperature for juvenile Atlantic salmon (c. 27°C), causing widescale abandonment of territory in favour of areas of cooler water (thermal refuges). This study aims to highlight the influence of thermal refuges on river‐scale abundance patterns. That is, do salmon parr adjust their distribution over time according to proximity to thermal refuges? Twelve reaches (seven reference: five refuge) were chosen along a 17‐km section of the Little Southwest Miramichi River in Canada. Reaches were sampled throughout the 2011 and 2012 summer periods; high temperature events were recorded during summer 2012 but not summer 2011. Multivariate principal component analyses indicated no discernible difference in habitat characteristics between the reach‐types under normal thermal conditions. However, reaches containing a thermal refuge had a significant increase in relative abundance of parr immediately after a series of high temperature events (water temperature >26°C) in 2012 (p = 0.034). This increase in relative abundance in refuge reaches was not present during the summer of 2011 when no temperature events occurred (p = 0.088), prior to the event of 2012 (p = 0.999), or at the late autumn survey following the 2012 event (p = 0.999). Difference in temperature between refuge and mainstem reaches significantly influenced the suitability of a tributary as a thermal refuge habitat (R2 = 0.84), with preference shown for cooler refuges. River‐wide thermal heterogeneity therefore plays a critical role in survival of juvenile salmon throughout summer months and is likely to become necessary under future climate change scenarios.

Swimming depths and water temperatures encountered by radio‐archival‐tagged Chinook Salmon during their spawning migration in the Yukon River basin

AbstractObjectiveHistorically, Chinook Salmon Oncorhynchus tshawytscha have supported important fisheries throughout the Yukon River basin, but dramatic declines in abundance since the late 1990s have resulted in smaller returns, severe reductions in harvests, and difficulties in meeting escapement goals. These observations coincide with major climatic changes in the northern Pacific, characterized by a general warming trend throughout the region. Our objective was to document the migratory patterns of the fish in relation to the environmental conditions encountered in order to assess the impact of climate change and help manage the returns.MethodsWe used radio‐archival tags to track the distribution and movements of adult Chinook Salmon returning to the Yukon River to spawn. The tags were equipped with sensors that recorded the swimming depth of the fish and water temperatures encountered during the upriver migration. Spawning ground surveys and fishery returns were used to recover the tags to download the sensor data.ResultNinety‐five (71.4%) of the 133 tags tracked upriver were recovered, including 35 (26.3%) returned by fishermen and 60 (45.1%) retrieved on the spawning grounds. Upriver movements were characterized by continuous and highly variable fluctuations in depth throughout the migration, ranging from <5 m to >20 m in the lower river and progressively less as fish moved upstream into shallower waters. Swimming depth was not influenced by time of day. Temperatures encountered by the fish were generally warmer in 2004, but this pattern was not consistent throughout the basin and was driven by conditions in the lower main stem, with temperatures frequently >18°C and periodically exceeding 21°C. There was no obvious behavioral response to the warm conditions, with comparable movements and survival rates when conditions were cooler. Temperatures in terminal tributaries often exceeded the upper range generally considered optimal during spawning (13°C), but signs of impaired behavior or prespawning mortality were not observed. A thermal diel pattern was evident as fish left the main stem and approached their spawning grounds, with temperatures declining from early evening to early morning and increasing during daylight hours, suggesting that assessments based on average daily temperature may not adequately reflect exposure to suboptimal conditions.ConclusionAlthough the fish during our study frequently encountered temperatures associated with adverse effect on salmon, impaired behavior and increased mortality were not evident. However, the current warming trend occurring throughout the northern Pacific is predicted to continue and may impact salmon populations more severely. Our findings provide a baseline for comparing past conditions and migratory patterns with those of present and future returns. Radio‐archival tags not only provided site‐specific information, but substantially increased the number of tags recovered, with a recovery rate considerably higher than reported for most archival tag studies. The ability to obtain larger samples and more representative results is a major advantage for addressing many resource issues currently facing fishery managers and local communities.

Geographic distribution, abundance, diet, and body size of invasive pink salmon (Oncorhynchus gorbuscha) in the Norwegian and Barents Seas, and in Norwegian rivers

AbstractWe report for the first time the geographic distribution, abundance, diet, and body size of invasive pink salmon (Oncorhynchus gorbuscha) in the Norwegian and Barents Seas and Norwegian coast and rivers. We found that pink salmon have spread throughout the Norwegian Sea and along the Norwegian coast, and abundance increased by several orders of magnitude in 2017, with no signs that it has peaked. Marine pink salmon diet comprised mainly fish larvae, amphipods, and krill, but their relative importance varied with geographic distribution. North of 67.5°N, Amphipoda, herring, and saithe were more important, while south of 67.5°N, Euphausiidae and mesopelagic fish abounded. Pink salmon body size was larger in the northern rivers, and to the north of the Norwegian Sea and the Barents Sea, relative to the southern rivers and sea areas. Pink salmon were feeding in the ocean during the winter and spring, and in coastal areas immediately before return to the rivers, but not after they had entered the rivers. There was no geographical pattern in the seasonal timing of river ascent. The geographic pattern in abundance and diet of pink salmon, as reported here, offer a measure of the ecological effect of the invasion.

Sockeye salmon Oncorhynchus nerka (Salmoniformes, Salmonidae) of continental coast of the Sea of Okhotsk

Summary the latest and the most complete data about the distribution of sockeye salmon in the rivers of the continental coast of the Sea of Okhotsk, its intraspecific structure and age composition are presented in the article, data on scale structure and growth rate are quoted for the first time.

Pink salmon distribution in Sweden: The calm before the storm?

Pink salmon distribution has recently expanded substantially across northern Europe. On the Swedish west coast, relatively few pink salmon have been observed to date; nonetheless, a notable rise in 2021 (70 observations). However, with no national monitoring together with a ceased Atlantic salmon commercial fishery, there is little opportunity to understand the extent of the spread in this region. Here, we present the current data and address the need for future monitoring and research in order to understand the potential impacts of this invasive species in Sweden's aquatic ecosystems.

Analysis of the commercial load on the autumn chum salmon population Amur Rivers in 2021

In this paper, a mathematical model is constructed that reflects the dependence of the distribution of autumn chum salmon along the spawning tributaries stream of the Amur River from fishing on the tracks of an extended anadromous migration.

Winter Distribution of Chum Salmon in the Gulf of Alaska: A Review

Winter Distribution of Chum Salmon in the Gulf of Alaska: A Review