Salmon Species Research Articles

Environmental DNA is an effective tool to track recolonizing migratory fish following large‐scale dam removal

AbstractEnvironmental DNA (eDNA) has emerged as a potentially powerful tool for use in conservation and resource management, including for tracking the recolonization dynamics of fish populations. We used eDNA to assess the effectiveness of dam removal to restore fish passage on the Elwha River in Washington State (USA). Using a suite of 11 species‐specific eDNA polymerase chain reaction (PCR) assays, we showed that most targeted anadromous species (five Pacific Salmon species and Pacific Lamprey) were able to pass upstream of both former dam sites. Multiscale occupancy modeling showed that the timing and spatial extent of recolonization differed among species during the four years of post‐dam removal monitoring. More abundant species like Chinook Salmon and Coho Salmon migrated farther into the upper portions of the watershed than less abundant species like Pink Salmon and Chum Salmon. Sampling also allowed assessment of potamodromous fish species. Bull Trout and Rainbow Trout, ubiquitous species in the watershed, were detected at all sampling locations. Environmental DNA from Brook Trout, a non‐native species isolated between the dams prior to dam removal, was detected downstream of Elwha dam but rarely upstream of the Glines Canyon Dam suggested that the species has not expanded its range appreciably in the watershed following dam removal. We found that eDNA was an effective tool to assess the response of fish populations to large‐scale dam removal on the Elwha River.

State of stocks of pacific salmons in the basin of Avacha Bay (southeastern Kamchatka) in 1985–2019

State of pacific salmon stocks is considered for the basins of the Avacha and Paratunka Rivers in 1985–2019. Significant decline of the stocks is noted that is associated with anthropogenic impact growth. Total number of producers for five salmon species in the Paratunka is almost twice higher than in the Avacha, with the largest portion of pink salmon, then chum salmon, lower portion of coho salmon, and the smallest portions of sockeye and chinook salmons, which need special protection. The main biological parameters of salmons are analyzed for both rivers, as body length, weight, fecundity, sex ratio and age structure, by species. Relationships between the parameters are revealed; their long-term trends are determined. Abundance of wildly and artificially hatched chum salmon is compared.

Assessing Accuracy and Bias of Protocols to Estimate Age of Pacific Salmon Using Scales

AbstractAccurate estimates of age composition are essential for fisheries management, but evaluation of protocols to estimate age data are rarely conducted. Herein, known‐age Pacific salmon Oncorhynchus spp. from six hatchery stocks were used to examine accuracy of multiple scale‐aging protocols and to assess how errors in age assignment may affect age composition estimated from scale data. Accuracy reached 1.0 for one stock of Coho Salmon Oncorhynchus kisutch, over 0.9 for three stocks of spring Chinook Salmon Oncorhynchus tshawytscha, and was no higher than 0.8 for two stocks of fall Chinook Salmon. For all hatchery stocks, accuracy increased and bias decreased when readers had auxiliary information about a fish's fork length and sex. Results suggest that a protocol that collects scales from above the lateral line, provides auxiliary information on fork length and sex, allows readers to exclude individuals for which age appears unclear, and uses an arbitrator to assign age when two initial readers disagree may produce the most accurate and unbiased age data from scales. This study highlights the importance of assessing patterns in age errors both qualitatively and quantitatively. A general pattern of overestimating age for younger age‐classes and underestimating age for older age‐classes was evident. This pattern in age errors could affect age composition estimates for adult Pacific salmon and other species with few (e.g., two to six) age‐classes. In addition, individual variation in demographic rates may affect individual patterns identified on scales; thus, for stocks with more extensive individual demographic variability, like fall Chinook Salmon stocks, accuracy may be lower and bias higher, resulting in less accurate estimates of age composition.

Molecular and immunological characterization of grass carp (Ctenopharyngodon idella) parvalbumin Cten i 1: A major fish allergen in Hong Kong.

Grass carp is the most commonly consumed fish species in Hong Kong. The allergenicity of grass carp and its allergen content are yet to be reported. This study characterized the major allergen in grass carp and investigated its allergenicity. Sixty-nine subjects with history of IgE-mediated allergic reaction to grass carp were recruited. The protein content in steamed grass carp extract was resolved by SDS-PAGE, and the major allergen was identified by immunoblotting with serum from subjects allergic to grass carp. The identity of allergen was elucidated by mass spectrometry and amino acid sequence obtained by amplifying the specific gene from cDNA library of grass carp. The cross-reactivity between parvalbumins from grass carp and other phylogenetically close (common carp) or commercially important (cod and salmon) species was investigated by competitive inhibition ELISA. A major IgE-binding protein was found at approximately 9kDa and identified as parvalbumin by immunoblotting and mass spectrometry. Grass carp parvalbumin was more allergenic than common carp, salmon, and cod parvalbumins despite sharing high sequence homology. This newly identified major allergenic parvalbumin isoform from grass carp was registered as Cten i 1 in the World Health Organization and International Union of Immunological Societies allergen database. Grass carp parvalbumin is identified as the major fish allergen in Hong Kong. The strong allergenicity of Cten i 1 contributes to the high IgE reactivity of grass carp. Grass carp, among other fish species, should be considered when managing fish-allergic patients.

Trophic responses of juvenile Pacific salmon to warm and cool periods within inside marine waters of Southeast Alaska

Marine growth and survival of juvenile Pacific salmon (Oncorhynchus spp.) have been linked to marine temperatures and feeding conditions during their first few months at sea. Therefore, understanding what salmon consume under varying environmental conditions is important to understanding how their growth and survival are affected by climate change. Here, we examined how warm/cool-phase variation in water temperature, salinity, wind speed, and pycnocline depth influenced the diet composition and quality of four species of juvenile Pacific salmon in Icy Strait (Southeast Alaska) from 2013 to 2017. During the five-year period, water temperatures shifted from a cool phase in 2013 to warm in 2014–2016, then back to cool in 2017. Overall, the diet composition and prey diversity varied among zooplanktivorous species (pink salmon O. gorbuscha, chum salmon O. keta, and sockeye salmon O. nerka) and piscivorous (coho salmon O. kisutch) species, with the exception of 2015, when euphausiids were the dominant prey for all four species. The summer of 2015 was notable for its deep pycnocline although it was not the warmest year in the study. Zooplankton nutritional quality was below average in 2015, but lipid intake by juvenile salmon appeared to be supplemented by the availability of larger euphausiid prey. Across years for all species, diet composition was weakly correlated with a combination of water temperature, salinity, and wind (Pearson correlation = 0.216). We conclude that while the marine heat wave altered the Gulf of Alaska ecosystem, within the range of variability observed during the study period, juvenile salmon were able to meet their energetic demands by switching to alternative prey.

Habitat affinity and density‐dependent movement as indicators of fish habitat restoration efficacy

AbstractConceptual and methodological tools from behavioral ecology can inform studies of habitat quality, and their potential for evaluating habitat restoration in conservation efforts is explored here. Such approaches provide mechanistic detail in understanding the relationship between organisms and their habitats and are thus more informative than correlations between density and habitat characteristics. Several Pacific salmon species have been the target of habitat restoration efforts for the past 2–3 decades, but most post‐restoration effectiveness studies have been limited to correlative data described above. In mark–recapture assays from four different study years, the affinity of sub‐yearling Chinook salmon (Oncorhynchus tschawytscha) and steelhead (O. mykiss) for stream pools restored with or created by engineered log structures was greater than that for pools without restoration, though with high interannual variability. From corresponding distribution and density data, it was clear that habitat affinity data are not always concordant with single observations of density. The same was true of the correlation between either affinity or density and physical characteristics of pools, although depth and current velocity had some explanatory power for both responses in Chinook. Movement into pools by Chinook during the assays indicated that restored pools can support more immigrants at a given density than can unrestored pools; however, no such pattern emerged for steelhead. Variation among individuals in body condition has implications for population‐wide fitness, and such low variation was correlated with stronger affinity for pools in Chinook regardless of restoration status. This suggests that pools may mediate habitat‐related trade‐offs and that restoring them might have a positive effect on fitness. Thus affinity, immigration, and condition data give much‐needed mechanistic indication of habitat selection for restored habitat via an apparent capacity increase and those potential fitness benefits. This is stronger support for restoration effectiveness than density differences alone because density data (1) may simply indicate redistribution of fish from poor to good habitats and (2) are not adequate to show correlations between restoration and positive change in traits correlated with fitness.

Landslide Susceptibility and Soil Loss Estimates for Drift Creek Watershed, Lincoln County, Oregon

ABSTRACTDrift Creek watershed, Lincoln County, Oregon, is a source of drinking water as well as a reproductive habitat for endangered salmon and trout species. Landslides, exacerbated by logging, are suspected as a cause of water quality deterioration in the watershed. To investigate the impact of landslides on water quality, we mapped landslide distribution and susceptibility, determined engineering properties of landslide-prone soil and rock, and estimated soil loss resulting from landslide-derived sediment within 30 m of Strahler third-order-or-higher streams in the watershed. We mapped 570 landslides using LiDAR imaging, orthophotographs, and field observations. We used logistic regression to determine the most significant variables contributing to landslide occurrence and to create a watershed-scale landslide susceptibility map. Siletz River Volcanics and the sedimentary Tyee Formation make up 85 percent of the watershed, with the sedimentary Yamhill and Nestucca formations making up the majority of the rest. Sedimentary rocks dominate in the Upper Drift Creek watershed, and volcanic dominate in the lower portion. The largest landslide deposits and the highest susceptibility occur in the sedimentary rock formations. The Siletz River Volcanics has a larger abundance of landslides than the sedimentary rock formations, but they are smaller in size with lower susceptibility of occurrence. The soil loss model indicates that the average annual soil loss from landslide deposits in the Upper Drift Creek watershed is 65 tons/acre/yr compared to 29 tons/acre/yr in the Lower Drift Creek watershed. The model also indicates that soil loss from areas along roads in the watershed is high.

Prioritizing conservation actions for Pacific salmon in Canada

Abstract Current investment in conservation is insufficient to adequately protect and recover all ecosystems and species. The challenge of allocating limited funds is acute for Pacific salmon Oncorhynchus spp. in Canada, which lack a strategic approach to ensure that resources are spent on actions most likely to cost‐effectively recover diminished populations. We applied the Priority Threat Management framework to prioritize strategies most likely to maximize the number of thriving Pacific salmon populations on the Central Coast of British Columbia, Canada. These included 79 genetically, ecologically and spatially distinct population groups called conservation units (CUs) for five salmon species. This region has high salmon biodiversity and spans the territories of four First Nations: the Heiltsuk, Nuxalk, Kitasoo/Xai'xais and Wuikinuxv. Using structured expert elicitation of Indigenous and other experts, we quantified the estimated benefits, costs and feasibility of implementing 10 strategies. Under a business‐as‐usual scenario (i.e. no additional investments in salmon conservation or management), experts predicted that only one in four CUs would have >50% chance of achieving a thriving status within 20 years. Limiting future industrial development in salmon habitats, which was predicted to safeguard CUs from future declines, was identified as the most cost‐effective strategy. Investment in three strategies: (a) removal of artificial barriers to fish migration, (b) watershed protection and (c) stream restoration—at 11.3M CAD per year—was predicted to result in nearly half (34 of 79) of the CUs having a >60% chance of meeting the conservation objective. If all conservation strategies were implemented, experts estimated a >50% probability of achieving a thriving status for 78 of 79 CUs, at an annual cost of 17.3M CAD. However, even with the implementation of all strategies, most sockeye salmon CUs were unlikely to achieve higher probability targets of reaching the objective. Policy implications. We illustrate how Priority Threat Management can incorporate the perspectives and expertise of Indigenous peoples and other experts to prioritize conservation strategies based on their cost, benefit and feasibility. Implementation of this framework can help safeguard and recover Pacific salmon in Canada, and could also be used to prioritize actions for other conservation issues globally.

Refuges and ecological traps: Extreme drought threatens persistence of an endangered fish in intermittent streams.

Recent droughts raise global concern over potential biodiversity loss and mitigating impacts to vulnerable species has become a management priority. However, drought impacts on populations are difficult to predict, in part, because habitat refuges can buffer organisms from harsh environmental conditions. In a global change context, more extreme droughts may turn previously suitable habitats into ecological traps, where vulnerable species can no longer persist. Here, we explore the impacts of California's recent record‐breaking drought on endangered juvenile Coho salmon. We estimated the variability of cumulative salmon survival using mark–recapture of nearly 20,000 tagged fish in intermittent stream pools during a 7‐year period encompassing drought and non‐drought conditions. We then determined the relative importance of physical habitat, streamflow, precipitation, landscape, and biological characteristics that may limit survival during drought. Our most striking result was an increase in the number of pools with reduced or zero survival during drought years and a coincident increase in spatial variability in survival among study reaches. In nearly half of the stream pools, salmon survival during drought was similar to mean survival of pools assessed during non‐drought years, indicating some pools had remarkable resistance (ability to withstand disturbance) to extreme drought. Lower survival was most attributable to longer duration of disconnection between upstream and downstream habitats, a consequence of increasing drought severity. Our results not only suggest that many pools sustain juvenile salmon in non‐drought years transition into ecological traps during drought but also highlight that some pools serve as refuges even under extreme drought conditions. Projected increases in drought severity that lead to longer droughts and greater habitat fragmentation could transform an increasing proportion of suitable habitats into ecological traps. Predicting future impacts of drought on Coho salmon and other sensitive species will require identification and protection of drought refuges and management strategies that prevent further habitat fragmentation.

What's the catch? Archaeological application of rapid collagen-based species identification for Pacific Salmon

Pacific salmon (Oncorhynchus spp.) are ecological and cultural keystone species along the Northwest Coast of North America and are ubiquitous in archaeological sites of the region. The inability to morphologically identify salmonid post-cranial remains to species, however, can limit our understanding of the ecological and cultural role different taxa played in the seasonal subsistence practices of Indigenous groups in the past. Here, we present a rapid, cost-effective ZooMS method to distinguish salmonid species based on collagen peptide mass-fingerprinting. Using modern reference material and an assemblage of 28 DNA-identified salmonid bones from the pre-contact Yup'ik site of Nunalleq, Western Alaska, we apply high-resolution mass spectrometry (LC-MS/MS) to identify a series of potential collagen peptide markers to distinguish Pacific salmon. We then confirm these peptide markers with a blind ZooMS analysis (MALDI-TOF-MS) of the archaeological remains. We successfully distinguish five species of anadromous salmon with this ZooMS approach, including one specimen that could not be identified through ancient DNA analysis. Our biomolecular identification of chum (43%), sockeye (21%), chinook (18%), coho (11%) and pink (7%), confirm the exploitation of all five available species of salmonid at Nunalleq.

A multi-frequency acoustic method to estimate mean standard length of juvenile salmon in the Discovery Islands, British Columbia

A method to estimate the mean standard length (L¯) of juvenile salmon in aggregations using multi-frequency (67 and 125 kHz) acoustic analysis was developed. An autonomous, single beam echosounder (Acoustic Zooplankton and Fish Profiler (AZFP), ASL Environmental Sciences) was deployed on the seafloor in Okisollo Channel, British Columbia during peak juvenile salmon migration season in 2015 and 2016. A positive correlation was found between the difference in the mean volume backscattering strength at 67 and 125 kHz (ΔMVBS67-125kHz) of juvenile salmon aggregations and the mean standard length of juvenile salmon collected with a purse seiner. A relationship of the form ΔMVBS67-125kHz=Alog10L¯+B was established. High variability was observed due to differences in salmon species composition and lower sampling sizes at the tail end of the migration periods, but a consistent relationship with comparable parameters was found. We suggest that this method is valuable particularly in the case of long-term monitoring of species that are known to aggregate in schools of individuals with similar size, as it can be used to estimate mean size without the use of invasive capture techniques.

Rheological Characteristics of Modified Paste from Salmon and Low Valued Breeds of Fishes

The article deals with issues related to the assessment of the rheological characteristics of modified pastes from salmon and low-valued fish breeds. The current trend of processing low-value fish raw materials is accompanied by a search for new technologies that have not been used before and develops in two directions: the development of methods for manufacturing traditional products based on low-value fish raw materials and the production of protein-containing products, such as protein isolates, hydrolysates, and food fish meal, protein mass, minced fish, etc. This is due to the fact that about a third of the total world catch of all of catched hydrobionts is used to the production of feed products and fish flour. At the same time, a lot of the small-sized fish breeds used for these purposes, although of small size, are little different in terms of chemical composition and nutritional value from those traditionally used, such as salmon species. So that they can be considered as an additional valued fish raw materials reserve for the preparation of food. The most promising recognized is the production of fish mince and the creation on its basis of various types of molded and structured products. The particular importance is the use of small-sized non-fatty fish, the mince from which is modified by the inclusion of food waste from valuable species of fish obtained by cutting of them. This allows you to send additional reserves of valuable food raw materials to produce food instead of using it for production of feeding.

Sublethal neurotoxicity of organophosphate insecticides to juvenile coho salmon

For decades, organophosphate (OP) insecticides have been used as chemical control agents in watersheds that support at-risk populations of Pacific salmon throughout western North America. Spray drift, runoff, and other processes transport OPs to critical surface water habitats for migratory salmonids. While most OPs share a common mechanism of action (i.e., inhibition of neuronal acetylcholinesterase, or AChE), they typically vary in toxic potency. Moreover, dose-response relationships for exposure and sublethal neurotoxicity (e.g., brain AChE inhibition) in salmonids have not been defined for many OPs. Here we exposed juvenile coho salmon (Oncorhynchus kisutch) to five common anticholinesterase insecticides (dimethoate, ethoprop, naled, phorate and phosmet) that are widely used on agricultural, commercial, residential, and public lands. Each of the five pesticides produced a concentration-dependent inhibition of AChE enzyme activity. The effective concentration for 50 % AChE inhibition (96-hr EC50) indicated the highest toxicity for phorate (EC50 = 0.57 μg/L) followed by phosmet (3.3 μg/L), naled (7.8 μg/L), ethoprop (90.6 μg/L) and dimethoate (273 μg/L). These findings can inform 1) relative hazard analyses for OP use near sensitive aquatic habitats, 2) predictions of sublethal OP mixture toxicity, and 3) ecological risk assessments for threatened or endangered species of Pacific salmon.

Gametogenesis of the Pacific salmon. 3. Comparative analysis of the state of gonads in juvenile Pacific salmon due to fertility formation

The ovarian condition was studied in juveniles of six species of the Pacific salmon of different ages, taken for research at four hatcheries, as well as captured in lakes and rivers in the Sakhalin Province and Kamchatka Territory. The formation of the older generation of germ cells, consisting of previellogenic oocytes, in females of the Pacific salmon ends at the age of 0+, in pink salmon, with a mass of about 0.2–0.3 g, in other species, with a mass of about 1–2 g. In all species, the replenishment of this generation ceases during the habitat of juvenile fish in fresh water. After the formation of the older generation of germ cells is completed and its number reaches a certain level characteristic of each fish species, two oogenesis processes, that are not externally related to each other, continue to be carried out in the ovaries. The first process is the growth of the older generation oocytes, which develop relatively synchronously, varying 1.5–2 times in diameter. The second process is the mitotic reproduction of the gonies, their entry into meiosis, and subsequent resorption at the stage of pachytene and early diplotene. The mitotic activity of the gonies is minimal in females of the pink salmon, and, in fact, it is not detected in the fish caught in the coast. In females of other species, a decrease in both mitotic activity and initiation of new meiotic cycles does not occur during the entire period of their habitat in fresh water.

Lipidomics study of rainbow trout (Oncorhynchus mykiss) and salmons (Oncorhynchus tshawytscha and Salmo salar) using hydrophilic interaction chromatography and mass spectrometry

In this study, three popularly consumed salmonids, king salmon (Oncorhynchus tshawytscha), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss), were studied from the aspects of texture, color, and lipidomics properties. The results indicated that the physical properties, such as texture and color, were susceptible to diet among these three salmonids. The difference of total lipid profile among these species was not obvious, while the phospholipids was significantly different. With the aim of further study the phospholipids from molecular level and make a better distinction among these three salmonids, a lipidomical method was established using hydrophilic interaction chromatography mass spectrometry, and the variance of phospholipid molecular species between salmons and rainbow trout was revealed by statistical analysis. The phospholipids of m/z 802.8 (PC 34:2) and m/z 834.8 (PC 36:0) could be tentatively used as potential markers for species identification. The significant variaties could be attributed to genetic origins, living environment, etc. The results provided the evidence that compared with other parameters that were easily affected by diet, the phospholipids of three salmonids was obviously different, which could be used to fast identify salmon species, and the issue of mislabeling should be administrated for food quality and safety.

Intra‐ and interspecific density‐dependent growth and maturation of Pacific salmon in the Bering Sea

AbstractMany studies have reported density‐dependent growth in single species, but density‐dependent growth can also occur between species when overlap in resource use occurs. We interrogate long‐term (1972–2010) monitoring data from the Bering Sea for evidence of intra‐ and interspecific density‐dependent growth among three species of Pacific salmon: sockeye, chum and pink. Partial correlation analysis, using intraspecific density as a control variable, identified interspecific density‐dependent growth among these three salmon species. As growth condition affects maturation, the maturity rates also depend on intra‐ and interspecific densities. Pacific salmon in the Bering Sea are of mixed origin, from North American and Asian rivers. As salmon return to their natal rivers, density‐dependent effects on their ocean growth and maturity during migration might have cascading effects on salmon returning to each continent, as salmon‐derived nutrients play important roles in riparian and terrestrial ecosystems.

Resilience of zooplankton communities in temperate reservoirs with extreme water level fluctuations

ABSTRACT The importance of zooplankton as a food resource for higher trophic levels, including threatened and endangered salmon species, highlights the need to improve our understanding of the mechanisms that structure reservoir food webs. Pelagic plankton are the dominant primary and secondary producers in reservoirs experiencing extreme water level fluctuations (WLFs). In these systems, we might expect WLFs to promote predictable and homogenized biotic communities. Here we explored whether spring and summer zooplankton communities are homogenized in Pacific Northwest (USA) flood-control reservoirs managed with annual extreme WLFs. In addition, we evaluated whether community resilience is present in a reservoir that has been drained annually since 2011 for salmon passage. We sampled 4 reservoirs during spring and summer, including 1 that was fully drained, resulting in a lotic riverine environment, for 1 week each fall from 2012 to 2016. We found low beta diversity across reservoirs, indicating homogenized communities. Additionally, we did not observe changes across sample years or increased differences in species composition compared to historical data. Instead, we observed strong seasonal transitions that were predictably repeated each year. Our findings support the hypothesis that extreme WLFs, under which these reservoirs have been managed for >50 years, may have structured reservoir zooplankton communities such that they are resilient to even more dramatic draining. Understanding how WLFs and reservoir draining may impact zooplankton will be critical to minimizing unintended consequences of reservoir management on aquatic food webs.

The current state of fish market in Ukraine

The fishing industry is an important component of the economy of Ukraine at the present stage of development. The development and implementation of the innovative technologies in fish farming and fish processing require mandatory and ongoing analysis of a fish market infrastructure. The demand for food protein, which is characterized by a balanced amino acid content is provided by fish and seafood at 20–30 %. The aim of this work was to understand a current state of a fish products market in Ukraine, its pricing and consumption. Based on the specialized literature the evaluation of a current state of fish and fish products consumption in Ukraine and own studies of the price category of fish products in Ukraine in recent years were conducted. We studied fish and fish products consumption per year per capita in Ukraine over the last 20 years, assortment of fish in Ukraine, the import of fish and fishery products by species, the product prices in UAH per kg both in previous years and today. According to international medical standards the annual consumption of fish and seafood should be 20 kg per person. At the same time in Ukraine according to the State Statistics Committee on the 01.01.2019 14.5 kg of fish and seafood came out per capita. In 2018–2019 herring traditionally remained a leader of consumption in Ukraine. Ukraine also imported such species of fish: mackerel, hake, herring, salmon, pilchards, pollack, capelin, sardines, notating. In addition pangasius, shrimp, blue whiting, mussels, squid, saury, Jack mackerel, sea bass, tuna, flounder, anchovies, smelt, cod, salmon and other species of fish, caviar and seafood are imported in Ukraine. The investigated assortment of fish in Ukraine is represented both domestic and imported products. The domestic production are: carp, pike, capelin, herring, mackerel, sprat, the imported products are: flounder, perch, pangasius, salmon, butter, hake, Pollock, capelin, nototenia, herring, mackerel, cod, tuna, tilapia (sole), sea trout, whiting and so forth. It is established that the condition of a fish market in Ukraine is affected by an unstable economic and political situation in the country, low solvency of the population, corruption and the high payables of the enterprises. In Ukraine a tendency towards a decrease in the volume of fish and fish products consumption by the population of Ukraine is observed annually, which is a consequence of the decline in fish catch and fish production, depreciation of fixed assets and a lack of financial support to the fishing industry.

More on the Factors that Limit the Abundance of Pacific Salmon (Oncorhynchus spp., Family Salmonidae) during the Ocean Phase of Their Life History

Two different viewpoints on the factors that limit the abundance of Pacific salmon in the sea and ocean phases of their life history are compared. According to traditional notions, food resources in sea and ocean epipelagic biotopes are limited and there is a severe competition for food between different species of the genus Oncorhynchus, which is particularly exhibited by the pink salmon O. gorbuscha. This results in a reduced abundance and worsening of some biological parameters of both pink and other salmon species. Negative anomalies of sea surface temperature, which decrease the food supply for these fish, are also traditionally considered as a factor that seriously restricts the salmon distribution in the marine life-history phase. A different point of view was expressed in the 1980s by the authors at TINRO-Center, based on comprehensive ecosystem studies of the Far Eastern seas and the North Pacific. According to this view, the food resources in the extensive salmon feeding range are not strictly limited and salmon play a secondary role in trophic webs within the subarctic epipelagic layer. The conclusion that salmon is a stenothermic fish was not confirmed, particularly for the cold-water conditions (salmon are found in the northern Bering Sea and the Sea of Okhotsk, with its harsh Arctic conditions, even in winter). New data obtained in 2018 support the latter viewpoint: in that year, the biomass of Russian salmon reached the historical maximum, primarily due to pink salmon, and the Russian catch of Pacific salmon was absolutely record-breaking, 677 900 t.

Threats to salmon and endangered fish species in Tysa river basin within trans Carpathian region (review)

Establish ways of creating, thoroughly investigate the threats and their level of salmon and endangered fish species Tysa River Basin within Zakarpattia region. Rate of change, diversity, distribution, the proportion of individual species, to the distribution of geographic elements on the principle of zoning and depending on environmental conditions. The study of threats to salmon and endangered species of fish in the river Tysa carried tributaries and in areas watercourse Transcarpathian region using generalized results of hydrological, ichthyological and toxicological studies. Number of species status of populations, evaluated on the basis of documents, monitoring of rivers, ichthyological data during in 2008–2014 years of control catching specialists Department of the use, reproduction of water bio-resources and regulation of fisheries in the Transcarpathian region, the State Administration of Environmental Protection in Zakarpattya region, published and unpublished sources, a survey of local fishermen. Collection and processing of materials performed by conventional methods. Comparison of species composition of fish fauna of the Tysa River Basin within Zakarpattia region on the results of previous studies and the current state of evidence that it has changed significantly. Analysis of data for 1926–2015 years revealed the presence of 77 species, which is 41.5 percent more than the same period in 1926. However, should point to the increase in the number and activities of various threats to salmon and other valuable fish species in our region. Established prolonged human pressure, pollution reduced the number of new European grayling and Trout v 13.4 times. There were 16 species, including salmon, listed in the Red Book of Ukraine. Ceased to meet sturgeon passage. Study threats operation populations of salmon and endangered species gives reason to believe that the level of destruction of natural resources, environmental pollution, depletion of the gene pool is too narrow to study hydro. For the first time a comprehensive assessment of threats to salmon, valuable and endangered local fish Transcarpathia in terms of various specific human impact of their pressure from environmental factors in the past and now. A study of the action of environmental factors and implementation of scientifically based measures to restore fish in close to natural. The results can be used in developing preservation methods, quantitative growth of populations of salmon and endangered species not only in Zakarpattya but also in the Carpathian region, water protection planning activities.