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Channel catfish, Ictalurus punctatus, have limited ability to synthesize Ω-3 fatty acids. The ccβA-msElovl2 transgene containing masu salmon, Oncorhynchus masou, elongase gene driven by the common carp, Cyprinus carpio, β-actin promoter was inserted into the channel catfish melanocortin-4 receptor (mc4r) gene site using the two-hit two-oligo with plasmid (2H2OP) method. The best performing sgRNA resulted in a knockout mutation rate of 92%, a knock-in rate of 54% and a simultaneous knockout/knock-in rate of 49%. Fish containing both the ccβA-msElovl2 transgene knock-in and mc4r knockout (Elovl2) were 41.8% larger than controls at 6 months post-hatch (p = 0.005). Mean eicosapentaenoic acid (EPA, C20:5n-3) levels in Elov2 mutants and mc4r knockout mutants (MC4R) were 121.6% and 94.1% higher than in controls, respectively (p = 0.045; p = 0.025). Observed mean docosahexaenoic acid (DHA, C22:6n-3) and total EPA + DHA content was 32.8% and 45.1% higher, respectively, in Elovl2 transgenic channel catfish than controls (p = 0.368; p = 0.025). To our knowledge this is the first example of genome engineering to simultaneously target transgenesis and knock-out a gene in a commercially important aquaculture species for multiple improved performance traits. With a high transgene integration rate, improved growth, and higher omega-3 fatty acid content, the use of Elovl2 transgenic channel catfish appears beneficial for application on commercial farms., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Glacier retreat is rapidly transforming some watersheds, with ramifications for water supply, ecological succession, important species such as Pacific salmon (Oncorhynchus spp.), and cultural uses of landscapes. To advance a more holistic understanding of the evolution of proglacial landscapes, we integrate multiple lines of knowledge starting in the early 1900s with contemporary data from the Taaltsux̱éi (Tulsequah) Watershed in British Columbia, Canada. Our objectives were to: 1) synthesize recent historical geography and Indigenous Knowledge, including glacier dynamics, and hydrology; 2) describe the limnology of a proglacial lake; 3) quantify decadal-scale downstream physical floodplain change; and 4) characterize riverine physical, chemical, and biological differences relative to distance from the proglacial lake. Since 1982, the Tulsequah Glacier has receded 0.07 km/yr, exposing a cold, deep, and growing proglacial lake. The downstream floodplain is rapidly changing; satellite imagery analysis revealed a 14 % increase in vegetation from 2003 to 2017 and Indigenous Knowledge described increases in vegetation and wildlife habitat over the last century. Contemporary measurements of physical-chemical water properties differed across sites representing the upper and lower watershed, and mainstem and off-channel habitats. Catches of juvenile salmonids in the upper watershed (closer to the glacier) were mostly limited to warmer, clearer groundwater-fed channels, whereas in the lower watershed there were salmonids in both groundwater-fed and mainstem habitats. There was limited zooplankton taxa diversity from the proglacial lake and benthic macroinvertebrates in the river. Collectively, our synthesis suggests that the transformation of proglacial landscapes experiencing rapid ice loss can be influenced by interlinked abiotic processes of glacier retreat, lake formation, and altered hydrology, as well as corresponding biological processes such as beaver repopulation, wetland formation, and riparian vegetation growth. These factors, along with expected increases to proglacial lake productivity and salmon habitat suitability, are an important consideration for forward-looking watershed management of glacier-fed rivers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Microplastics are increasingly prevalent in marine systems and are a growing concern as a marine pollutant and contaminant with consequences for high trophic level consumers, including humans. Given evidence that links plastics to degraded ecosystem functioning and organismal health, there is increased interest in understanding the prevalence, fate and consequences of marine plastics. Microplastics contain and absorb harmful chemicals which may serve as endocrine disruptors and have negative implications for growth, reproductive health, and longevity. To expand current knowledge on microplastics in coastal marine ecosystems and the potential for biomagnification in marine food webs, we conducted stomach analyses of microplastics in Pacific salmon (Oncorhynchus spp.) and Pacific sand lance (Ammodytes personatus), an important prey for salmon. Prevalence of microplastics was substantial; 77 % of all salmon and 25 % of all sand lance stomachs contained at least one microplastic. Fish were sampled at multiple sites throughout the inland Salish Sea, including beaches and sediment bedforms for Pacific sand lance and open-water pelagic habitat for Pacific salmon. Pacific sand lance sampled at beach sites had more microplastics compared to those sampled in subtidal sediments and there were more plastics in sand lance at a protected beach site as compared to an exposed beach site. Prevalence of plastics in salmon differed according to species and included analyses of pink salmon (Oncorhynchus gorbuscha), Chinook (Oncorhynchus tshawytscha), and Coho salmon (Oncorhynchus kisutch); plastics were predominantly fibers in all species, though there were relatively higher rates of ingestion of films and particles in Chinook. Comparisons between plastic concentrations and stomach fullness indicated a slight negative trend, suggesting that plastics may be retained. Further investigation is needed to develop a more thorough understanding of the prevalence and fate of microplastics in coastal marine systems such as the Salish Sea, their concentration within marine food webs, and the implications for species targeted in fisheries., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Pacific salmon transfer large quantities of material to tributaries during their spawning migrations, including carcass tissue and labile nutrients but also persistent organic pollutants (POPs) and heavy metals. We conducted a Before-After-Control-Intervention experiment by adding salmon carcasses and eggs to a Michigan (USA) stream that had never received inputs from non-native salmon to understand the bioaccumulation and persistence of biotransported contaminants. Our experimental outcomes were compared to previous studies using meta-analysis. Coincident with the introduction of salmon, the PCB and DDE burden of resident trout significantly increased. However, we did not observe changes in total mercury (Hg). Two years after the salmon addition experiment concluded, resident trout POP concentrations had returned to pre-addition levels, with no difference between the treatment and control reaches. Analysis of effect sizes suggested that the contaminant response observed in our experiment is consistent with field survey observations. Our study suggested that the consumption of salmon eggs drove the increase in POP burden of resident trout while Hg bioaccumulation was influenced by watershed sources. Critically, our study suggests that ecosystems are capable of quickly recovering from POP inputs from species migrations if contaminant sources are removed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)

The frequency of dissolved oxygen depletion events (hypoxia) in coastal aquatic ecosystems has risen dramatically since the late 20th century, yet the causes and consequences of hypoxia for some culturally and economically important species remain poorly understood. In rivers, oxygen depletion can be caused by high densities of spawning Pacific salmon (Oncorhynchus spp.) consuming oxygen faster than can be replaced by reaeration. This process may be exacerbated when salmon densities are artificially inflated, such as when hatchery-origin salmon stray into rivers instead of returning to hatcheries. In Southeast Alaska, hatchery salmon production has increased rapidly since the 1970s, with over 553 million chum salmon (O. keta) and 64 million pink salmon (O. gorbuscha) released in 2021 alone. Straying is pervasive in streams with outlets <25 km from nearshore marine hatchery release sites. Using a previously ground-truthed mechanistic model of dissolved oxygen dynamics, we examined how water temperature and low-flow channel hydraulics contribute to hypoxia vulnerability. We then applied the model to predict hypoxia vulnerability for watersheds within 25 km of hatchery salmon release points, where straying salmon spawner densities are expected to be higher and promote dissolved oxygen depletion. Our model predicted that low-gradient stream reaches, regardless of water temperature, are the most prone to hypoxia due to low reaeration rates. Our spatial analysis determined that nearly 17,000 km of anadromous-accessible stream reaches are vulnerable to high densities of hatchery-origin salmon based on 2021 release sites. To our knowledge, this study is the first to map the spatial variation of hypoxia vulnerability in anadromous watersheds, identify habitat conditions most likely to promote hypoxia, and provide a repeatable analytical approach to identify hypoxia-prone stream reaches that can be updated as empirical data sets improve., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The toxicity of ZnO nanoparticles (ZnO NPs) in aquatic organisms has been extensively studied, but little information is available on the effects associated with their interaction with other contaminants. In this context, the in vitro effects of co-exposure of chlorpyrifos (CPF) and ZnO NPs on fish-derived cells were investigated. A selection of concentrations was tested in single and binary exposures: CPF (0.312 - 75 mg/L) and ZnO NPs (10 - 100 mg/L). Cytotoxicity was measured using commonly used cellular endpoints: Alamar Blue/CFDA-AM for viability and plasma membrane integrity, NRU for lysosomal disruption and MTT for mitochondrial function. In addition, specific mechanisms of toxicity for CPF and ZnO NPs were tested: acetylcholinesterase (AChE) activity and ROS generation, respectively. AChE was by far the most sensitive assay for single exposure to CPF. There was no concentration-response relationship for ROS after single exposure to ZnO NPs, but 10 mg/L produced significant effects only for this cellular endpoint. Co-exposure of CPF with 10 m/L of ZnO NPs produced significant effects in almost all endpoints tested, which were enhanced by co-exposure with 100 mg/L of ZnO NPs. AChE testing of additional co-exposures with bulk ZnO, together with the application of the Independent Action (IA) prediction model, which allowed us to draw more in-depth conclusions on the toxicological behavior of the mixture. Synergism was observed at 0.625 mg/L CPF concentration and antagonism at 5 mg/L CPF in mixtures containing 100 mg/L of both ZnO NPs and bulk ZnO. However, more cases of synergism between CPF and ZnO NPs occurred at intermediate CPF concentrations, demonstrating that nano-sized particles have a more toxic interaction with CPF than bulk ZnO. Therefore it can be argued that in vitro assays allow the identification of interaction profiles of NP-containing mixtures by achieving multiple endpoints with a large number of concentration combinations., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

The article discusses the study that determines the increase of plasma vitellogin concentration in rainbow trout Oncorhynchus mykiss, conducted in Norway. The study is intended to examine whether effluents from an oil refinery with new best available technology for the effluent treatment may contain estrogenic substances. It involves the selection of the effluent from the ESSO-Slagentangen Oil Refinery, due to the toxicity of process chemicals and effluents from this refinery, which has been studied, and since this refinery is located at the outlet of the Oslofjord. The results concluded that oil refineries may contain bioactive substances, even with the best available effluent treatment technology.

Fish from commercially farmed stocks are often released into the natural environment to supplement wild populations. This practice is often applied to salmonid fish as they are an essential fishery resource and also used for recreational angling. However, farmed fish tend to show lower survival rates after release than wild fish. For this reason, the release of semi-wild fish is increasingly used in Japan; these fish are generated using female fish from domesticated stocks and male fish of wild origin. The survival rate of released semi-wild fish is higher than that of farmed fish, but the reason for this is unknown. This study compared the metabolism and swimming performance of semi-wild and farmed masu salmon (Oncorynchus masou). The analyses showed that resting metabolic rate (RMR), maximum metabolic rate (MMR) and swimming speeds that minimize energy costs of travel (optimal swimming speed) were higher in semi-wild fish than in farmed fish. Critical swimming speed did not differ significantly between the two groups of fish. Semi-wild fish with high RMR may have a social status advantage over farmed fish because a previous study reported that SMR, which is the value closest to basal metabolism significantly affects feeding motivation. This means that individuals with higher social status may be more motivated to feed. As RMR is proportional to food requirements, then release programs should be planned taking food resources at the release site into consideration., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: None declared., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The present study aimed to assess the biotransport of POPs, including OCPs and PCBs, by Pacific salmon (genus Oncorhynchus) on the northwestern Pacific Ocean. In 2008-2012, the Amur River basin, the eastern Kamchatka, and the mainland coast of the Sea of Okhotsk received the largest amounts of pesticides. In 2018, the transport of OCPs to the Russian northwestern Pacific reached only 1 kg, and the total OCP levels in muscles of fish from this region were significantly lower than in previous years. The average concentration of PCBs for all species under study differed from that of OCPs, with the highest concentration recorded from sockeye salmon. In 2018, pink salmon brought the largest amount of PCBs to the Russian northwestern Pacific. Coastal water pollution has decreased significantly in recent years due to the ban on the use of POPs in the Northwest Pacific (according to the measurements in 2010 and 2018)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

In arid ecosystems, available water is a critical, yet limited resource for human consumption, agricultural use, and ecosystem processes-highlighting the importance of developing management strategies to meet the needs of multiple users. Here, we evaluated how water availability influences stream thermal regimes and life-history expressions of Lahontan cutthroat trout (Oncorhynchus clarkii henshawi) in the arid Truckee River basin in the western United States. We integrated air temperature and stream discharge data to quantify how water availability drives stream temperature during annual spawning and rearing of Lahontan cutthroat trout. We then determined how in situ stream discharge and temperature affected adult spawning migrations, juvenile growth opportunities, and duration of suitable thermal conditions. Air temperatures had significant, large effects (+) on stream temperature across months; the effects of discharge varied across months, with significant effects (-) during May through August, suggesting increased discharge can help mitigate temperatures during seasonally warm months. Two models explained adult Lahontan cutthroat trout migration, and both models indicated that adult Lahontan cutthroat trout avoid migration when temperatures are warmer (~ > 12 °C) and discharge is higher (~ > 50 m 3 *s -1 ). Juvenile size was best explained by a quadratic relationship with cumulative degree days (CDD; days>4 °C) as size increased with increasing CDDs but decreased at higher CDDs. We also found an interaction between CDDs and discharge explaining juvenile size: when CDDs were low, higher discharge was associated with larger size, but when CDDs were high, higher discharge was associated with smaller size. Stream temperatures also determined the duration of juvenile rearing, as all juvenile emigration ceased at temperatures >24.4 °C. Together, our results illustrated how stream discharge and temperature shape the life-history of Lahontan cutthroat trout at multiple stages and can inform management actions to offset warming temperatures and facilitate life-history diversity and population resilience., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier B.V.)

Pacific salmon Oncorhynchus spp. hatcheries in British Columbia (BC) have been the major activity of the Salmonid Enhancement Program since 1977. However, the present diminished abundance of Pacific salmon and loss of fisheries in BC called for a review of hatchery effectiveness. The Pacific Salmon Foundation conducted a review resulting in 15 reports publicly available on the Pacific Salmon Foundation marine science website. The review includes evaluations of effectiveness of hatchery production, evidence of interactions with natural salmon populations (including rebuilding natural populations with hatchery‐produced salmon), and future opportunities via genomics. Beyond the estimation of juvenile production and contribution to catches and spawning escapements, the ability to assess effectiveness was limited. The assessments of interactions provided a few examples of positive outcomes, but most were negative. The lack of comparative assessments in purely wild populations seriously limits interpretations of hatchery–wild interactions. Future evaluations of the hatchery effectiveness require more quantitative and integrated assessments of hatchery and wild salmon, open data sharing for public review or research, and related studies could benefit from application of new genomic technologies. This paper presents recommendations to address these needs and calls for regularized reviews of the Salmonid Enhancement Program and its net value to sustainability of BC's Pacific salmon. [ABSTRACT FROM AUTHOR]

Aquatic systems are warming and exceeding upper thermal limits (UTLs) for many fish species, yet understanding how they inform resilience to climate change is challenging. Using Pacific salmon (Oncorhynchus spp.) as a model, we conducted a systematic review involving 168 papers investigating UTL in five species. We found considerable variation in UTL among species, within species and across life stages; largely attributed to methodological approaches (e.g. CTmax/UILT, Aerobic/Cardiac Scope, Thermal Migration Barriers, Rearing Mortality, Thermal Preference/Avoidance). Given that each method has strengths and weaknesses owing to logistics, time scale and ecological realism, we offer a new framework for assessing vulnerability to warming that stresses the importance of considering UTL metrics in the context of intended use (i.e. the development of management guidelines, projections of future persistence and survival) and what aspect (physiological or behavioural) of thermal response a metric investigates. Comparing studies with identical UTL approaches revealed that within species, UTL was higher for populations historically encountering higher temperatures—suggesting local thermal adaptation. Within populations, UTL differed across the lifecycle, being highest in fry and lowest in embryo and migrating adults, but this was not universal. For spawning Pacific salmon, UTL has not been assessed and few studies have examined estuarine and marine stages. Ultimately, this data gap limits the life‐history thermal perspectives that can be drawn and may indicate a broader gap for all fishes, given that Pacific salmon are among the most well‐studied species. Our framework illustrates the inherent and methodological inconsistencies in UTL and offers a guide for how thermal limits can best be used to assess the warming tolerance and vulnerability of fishes. [ABSTRACT FROM AUTHOR]

No effective cryopreservation technique exists for fish eggs and embryos; thus, the cryopreservation of germ cells (spermatogonia or oogonia) and subsequent generation of eggs and sperm would be an alternative solution for the long-term preservation of piscine genetic resources. Nevertheless, in our previous study using rainbow trout, we showed that recipients transplanted with XY spermatogonia or XX oogonia produced unnatural sex-biased F1 offspring. To overcome these obstacles, we transplanted immature germ cells (XX oogonia or XY spermatogonia; frozen for 33 days) into the body cavities of triploid hatchlings, and the transplanted germ cells possessed a high capacity for differentiating into eggs and sperm in the ovaries and testes of recipients. Approximately 30% of triploid recipients receiving frozen germ cells generated normal salmon that displayed the donor-derived black body color phenotype, although all triploid salmon not receiving transplants were functionally sterile. Furthermore, F1 offspring obtained from insemination of the oogonia-derived eggs and spermatogonia-derived sperm show a normal sex ratio of 1:1 (female:male). Thus, this method presented a critical technique for practical conservation projects for other teleost fish species and masu salmon., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

A lognormal error is usually assumed in the traditional stock-recruitment (SR) analysis. In this paper, I demonstrate that a positive bias results when an SR model with lognormal error is used for fish recruitment prediction. Not only is this bias exponentially dependent on the structure of the model's residual variance and the historical SR data, it is also dependent on the specific value of spawner biomass used. I then derive a bias correction that is asymptotically unbiased with a finite-sample bias that is practically zero. Data from two Pacific salmon populations, southeast Alaska pink salmon Oncorhynchus gorbuscha and Chilko Lake sockeye salmon O. nerka, are used to demonstrate this approach. The results show that the relative bias is about 10% for a spawning biomass within the historical range and that the bias is substantial outside that data range. However, with the proposed bias correction, the bias is negligible both within (<0.1%) and outside of (<0.3%) the data range. [ABSTRACT FROM AUTHOR]

Introduction: Soybean lecithin (SBL) is usually added to aquafeed as a phospholipids source because aquatic animals including crustaceans and fish cannot synthesize phospholipids. Hence, this study aimed to evaluate the effects of different levels of dietary soybean lecithin (a source of phospholipid) on the antioxidant defense system of female and male broodstock, ovum, eggs and the first stage swimming larvae of rainbow trout, Oncorhynchus mykiss. Materials and methods: For this purpose, fish were fed four isoproteic and isolipidic diets containing graded levels of soybean lecithin (SBL) as a source of phospholipid (including 0, 2, 4 and 6%) for 190 days. At the end of the experiment, the samples of serum, ovum, egg and larvae were collected for antioxidant activity of CAT, SOD and MDA analyses. Results and discussion: The results obtained showed that 4-6% dietary SBL supplementation significantly increased the antioxidant enzymes activity, including catalase and superoxide dismutase in the fish blood serum, eggs, and larvae compared to the control. On the other hand, MDA level in the control group was higher than in the other treatments (p<0.05). Thus, considering the data on improved the activity of antioxidant enzymes, it is recommended to include SBL at 4-6% in rainbow trout broodstock diet. Conclusion: It is concluded that an optimal lecithin content in the diet of rainbow trout broodstock can lead to improving quality of ova and larval immune system. Funding: This work was supported by the Office of Vice-Chancellor for Research and the Artemia and Aquaculture Research Institute of Urmia University in the framework of the postdoctoral research of Dr. Fatemeh Jafari (grant number 98/A/007). [ABSTRACT FROM AUTHOR]

For almost 200 years, the taxonomy of cutthroat trout (Oncorhynchus clarkii), a salmonid native to Western North America, has been in flux as ichthyologists and fisheries biologists have tried to describe the diversity within these fishes. Starting in the 1950s, Robert Behnke reexamined the cutthroat trout and identified 14 subspecies based on morphological traits, Pleistocene events, and modern geographic ranges. His designations became instrumental in recognizing and preserving the remaining diversity of cutthroat trout. Over time, molecular techniques (i.e. karyotypes, allozymes, mitochondrial DNA, SNPs, and microsatellite arrays) have largely reinforced Behnke's phylogenies, but have also revealed that some relationships are consistently weakly supported. To further resolve these relationships, we generated de novo transcriptomes for nine cutthroat subspecies, as well as a Bear River Bonneville form and two Colorado River lineages (blue and green). We present phylogenies of these subspecies generated from multiple sets of orthologous genes extracted from our transcriptomes. We confirm many of the relationships identified in previous morphological and molecular studies, as well as discuss the importance of significant differences apparent in our phylogenies from these studies within a geological perspective. Specific findings include three distinct clades: (1) Bear River Bonneville form and Yellowstone cutthroat trout; (2) Bonneville cutthroat trout (n = 2); and (3) Greenback and Rio Grande cutthroat trout. We also identify potential gene transfer between Bonneville cutthroat trout and a population of Colorado River green lineage cutthroat trout. Using these findings, it appears that additional groups warrant species‐level consideration if other recent species elevations are retained. [ABSTRACT FROM AUTHOR]

Over the last 10 years, the spawning population of invasive pink salmon (Oncorhynchus gorbuscha) has increased in the river systems in northern Norway to a level that is causing concern about their impact on endemic fauna and ecosystem processes. The scale of transfer of pink salmon carcasses into the terrestrial ecosystem is likely to be a key determinant of terrestrial impact. Bears (Ursus sp.) are responsible for most such transfers in North America but are rare in Norway. The white‐tailed eagle (Haliaeetus albicilla) is common however, and a candidate to be a main cause of such transfers. To evaluate this hypothesis, data on the abundance of white‐tailed eagles and pink salmon were collected along the river Skallelv in northern Norway in 2021, a year the pink salmon spawned in the river, and in 2022, a year no pink salmon spawned in the river. The abundance of white‐tailed eagles along the river was much higher the year pink salmon spawned in the river. Furthermore, white‐tailed eagles were observed aggregating and catching pink salmon where and when pink salmon were present at the spawning and post‐spawning stages. Based on our observations, we suggest that the white‐tailed eagle is the main species involved in the transport of pink salmon from the river into the riparian zone in northern Norway and that other scavengers, in particular the red fox (Vulpes vulpes) and common raven (Corvus corax), play an important role in transporting pink salmon carcasses from the riparian zone to the wider terrestrial ecosystem. [ABSTRACT FROM AUTHOR]

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Dam removal is often proposed for restoration of anadromous salmonid populations, which are in serious decline in California. However, the benefits of dam removal vary due to differences in affected populations and potential for environmental impacts. Here, we develop an assessment method to examine the relationship between dam removal and salmonid conservation, focusing on dams that act as complete migration barriers. Specifically, we (1) review the effects of dams on anadromous salmonids, (2) describe factors specific to dam removal in California, (3) propose a method to evaluate dam removal effects on salmonids, (4) apply this method to evaluate 24 dams, and (5) discuss potential effects of removing four dams on the Klamath River. Our flexible rating system can rapidly assess the likely effects of dam removal, as a first step in the prioritization of multiple dam removals. We rated eight dams proposed for removal and compared them with another 16 dams, which are not candidates for removal. Twelve of the 24 dams evaluated had scores that indicated at least a moderate benefit to salmonids following removal. In particular, scores indicated that removal of the four dams on the Klamath River is warranted for salmonid conservation. Ultimately, all dams will be abandoned, removed, or rebuilt even if the timespan is hundreds of years. Thus, periodic evaluation of the environmental benefits of dam removal is needed using criteria such as those presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel approach for determining the probable co-occurrence of juvenile salmon or steelhead with agricultural pesticides and apply it to spring Chinook (Oncorhynchus tshawytscha) salmon in the Willamette Basin, Oregon. We adapted a published exposure analysis framework by explicitly considering fish migration among habitat units and assuming that habitat use is proportional to habitat quality. Temporal variability in habitat use was accounted for via biweekly time steps over the entire period when a single brood was expected to spawn until the last juvenile migrated to sea. Spatial variability was accounted for at the watershed and reach scale. Exposure to 6 acetylcholinesterase-inhibiting insecticides at any life stage was expressed in terms of the future adults (adult-equivalents; AEQ). Several datasets were available to inform our framework with input values on extent of spring Chinook fish use, habitat quality preferred by juvenile spring Chinook, choice of juvenile life-history pathways, timing of emergence, and timing of migration either in-stream or to sea. We used insecticide concentration profiles constructed from available monitoring data to demonstrate the effect of accounting for variation in space and time on predicted exposure to chemical residues. In contrast to the assumption commonly used in screening-level risk assessments that the entire population in a watershed is exposed, available data applied to our model framework indicate that a small fraction of AEQ juveniles in the Willamette Basin would co-occur with detectable concentrations of the 6 insecticides. Overall, our results indicated that the use of a spatially and temporally explicit framework yields a better understanding of the proportion of organisms potentially impacted by agricultural pesticides., (Copyright © 2011 SETAC.)

The impressive †Oncorhynchus rastrosus of the Pacific Northwest's Miocene and Pliocene eras was the largest salmonid ever to live. It sported a hypertrophied premaxilla with a pair of enlarged teeth which the original describers reconstructed as projecting ventrally into the mouth, leading them to assign the species to "Smilodonichthys," a genus now in synonymy. Through CT reconstruction of the holotype and newly collected specimens, we demonstrate that the famed teeth projected laterally like tusks, not ventrally like sabers or fangs. We also expand the original description to characterize sexual dimorphism in mature, breeding individuals. Male and female †Oncorhynchus rastrosus differ in the form of the vomer, rostro-dermethmoid-supraethmoid, and dentary, much as do other extant species of Oncorhynchus. Male specimens possess a more elongate vomer than do females, and female vomers have concave ventral surfaces and prominent median dorsal keels. The dentary of females has no evidence of a kype, though some specimens of †O. rastrosus have a non-uniform density mesial to the tooth bed, which we interpret as a male kype. Unlike extant Oncorhynchus, male and female †O. rastrosus do not differ in premaxilla shape. Because male and females possess hypertrophied premaxillae and lateral premaxillary spikes, the former common name "Sabertoothed Salmon" no longer reflects our understanding of the species' morphology. Accordingly, we redub †O. rastrosus the Spike-Toothed Salmon and postulate that its spikes were multifunctional, serving as defense against predators, in agonism against conspecifics, and as a practical aid to nest construction. [ABSTRACT FROM AUTHOR]

The value of estuaries as nursery habitat for juvenile anadromous salmon is likely variable across estuaries and species. Here, we compiled published empirical data on juvenile salmon estuarine growth and residency. We aimed to quantify the range and variability of these aspects for five species of Pacific salmon across estuaries, methodologies, and life histories. The majority of studies focused on Chinook and coho salmon, largely from their southern range. While there is some evidence of higher growth in wild-origin fish relative to hatchery-origin fish, the wide range of metrics employed made identification of trends among life histories challenging, and unification of reporting could strengthen future research. Different salmon life histories exhibited different residencies, with natural-origin subyearling coho exhibiting the longest mean residency (∼3 months) and 1+ sockeye salmon exhibiting the shortest (3.7 days). Across life histories, hatchery fish exhibited much shorter estuary residencies than wild fish. Collectively, our review highlights key patterns in salmon estuary ecology, identifies knowledge gaps, and lays the foundation for future studies to quantify the importance of estuaries for specific salmon. [ABSTRACT FROM AUTHOR]

As Pacific salmon (Oncorhynchus spp.) decline across much of their range, it is imperative to further develop minimally invasive tools to quantify population abundance. One such advancement, trans‐generational genetic mark–recapture (tGMR), uses parentage analysis to estimate the size of wild populations. Our study examined the precision and accuracy of tGMR through a comparison to a traditional mark–recapture estimate for Chilkat River Chinook salmon (O. tshawytscha) in Southeast Alaska. We examined how adult sampling location and timing impact tGMR by comparing estimates derived using samples collected in the lower river mainstem to those using samples obtained in upriver spawning tributaries. Results indicated that tGMR estimates using a representative sample of mainstem adults were most concordant with, and 3% more precise than, the traditional mark–recapture estimate for this stock. Importantly, the timing and location of adult sampling were found to impact abundance estimates, depending on what proportion of the population dies or moves to unsampled areas between downriver and upriver sampling events. Additionally, we identified potential sources of bias in tGMR arising from violations of key assumptions using a novel individual‐based modeling framework, parameterized with empirical values from the Chilkat River. Simulations demonstrated that increased reproductive success and sampling selectivity of older, larger individuals, introduced negative bias into tGMR estimates. Our individual‐based model offers a customizable and accessible method to identify and quantify these biases in tGMR applications (https://github.com/swrosenbaum/tGMR%5fsimulations). We underscore the critical role of system‐specific sampling design considerations in ensuring the precision and accuracy of tGMR projects. This study validates tGMR as a potentially useful tool for improved population enumeration in semelparous species. [ABSTRACT FROM AUTHOR]

Local extirpations of Pacific salmonOncorhynchusspp. and steelheadO. mykiss, often due to dams and other stream barriers, are common throughout the western United States. Reestablishing salmonid populations in areas they historically occupied has substantial potential to assist conservation efforts, but best practices for reintroduction are not well established. In this paper, we present a framework for planning reintroductions designed to promote the recovery of salmonids listed under the Endangered Species Act. Before implementing a plan, managers should first describe the benefits, risks, and constraints of a proposed reintroduction. We define benefits as specific biological improvements towards recovery objectives. Risks are the potential negative outcomes of reintroductions that could worsen conservation status rather than improve it. Constraints are biological factors that will determine whether the reintroduction successfully establishes a self-sustaining population. We provide guidance for selecting a recolonization strategy (natural colonization, transplanting, or hatchery releases), a source population, and a method for providing passage that will maximize the probability of conservation benefit while minimizing risks. Monitoring is necessary to determine whether the reintroduction successfully achieved the benefits and to evaluate the impacts on nontarget species or populations. Many of the benefits, especially diversity and the evolution of locally adapted population segments, are likely to accrue over decadal time scales. Thus, we view reintroduction as a long-term approach to enhancing viability. Finally, our review of published salmonid reintroduction case studies suggests that large uncertainties remain in the success of reintroduction in establishing self-sustaining populations, particularly for programs employing active methods. Received September 10, 2012; accepted August 30, 2013 [ABSTRACT FROM AUTHOR]

This paper presents original data regarding: the three-dimensional modelling of rainbow trout (Oncorhynchus mykiss) and sea bass (Dicentrarchus labrax) IL-1beta, the modelling of trout IL-1 receptor type I (IL-1RI) and the modelling of trout IL-1beta bound to its receptor. The 3D models of trout and sea bass IL-1beta molecules were predicted by comparison with those already available of human and mouse, and, in both cases, a structure consisting of a beta-trefoil fold was obtained, a motif well conserved during evolution of IL-1beta-related proteins. Moreover, a model for the rainbow trout IL-1 receptor alone and complexed with IL-1beta was predicted and compared to the murine model. Both ligand-receptor complex models were compared with the known crystal structure of the human IL-1beta/IL-1R complex. A cross-interaction of trout IL-1beta with the mouse receptor was also simulated. Such analysis and the predicted interaction energies calculated from the models have helped to explain the different biological efficacies of mammalian and fish IL-1beta molecules in assays based on mammalian target cells. The obtained data are discussed on the basis of evolutionary and applied perspectives.

This paper describes a methodology for estimating the take of upstream migrating adult chum salmon (Oncorhynchus keta) caused by confined underwater rock blasting. Because these fish are listed under the Endangered Species Act, it is unlawful to take (i.e., harm, capture, collect, injure, kill, etc.) them without a federal permit. In the permit for an underwater blasting project to deepen a 2 km section of the Columbia River navigation channel linking Portland, Oregon, to the Pacific Ocean, regulators defined take as the mortality of adult chum salmon due to underwater blasting. They required monitoring to estimate take to track compliance with the permit. Conventional predictive models of fish mortality from underwater blasting depend on data about the explosive charges; however, such data for this project were not available for proprietary reasons. Therefore, an innovative approach had to be conceived. The dose-exposure-response methodology we developed provided an unobtrusive, science-based methodology for monitoring and near real-time reporting of adult chum salmon take. We applied the methodology for 99 blasting events from November 1, 2009, through February 5, 2010, in the lower Columbia River (rkm 139–141). The mean absolute peak pressure in underwater sound generated by blast events was 151,685 Pa (22 psi) at a range of 42.7 m. The estimated cumulative take for the project was 0.126 adult chum salmon, far below the 10-fish mortality limit regulators set for the project. We propose that this dose-exposure-response methodology be considered wherever underwater blasting has the potential to have an adverse effect on important fish species. • Innovative dose-exposure-response methodology estimates take (fish mortality) from blasting. • Unobtrusive methodology allows daily reporting of results required by regulating agencies. • Methodology applicable where there is regulatory concern about impacts of impulsive underwater sound on fish. [ABSTRACT FROM AUTHOR]