Современная оценка факторов, определяющих эффективность воспроизводства рыб в низовьях р. Урал

The material was the data of trawl-acoustic surveys and fishing nets in the reservoirs of the Tver region during resource research in 2007–2022, as well as archival data. As a result of the closure of the fishery by the State Committee of the Russian Federation for Fisheries in 2007, in order to preserve and more efficiently use the ichthyofauna of rivers, lakes, reservoirs, there was a decrease in commercial fish stocks in the reservoirs of the Tver region. Also, due to an increase in the concentration of some fish species (bream, bream), infection with ligulosis has increased. Periodic outbreaks of this disease have already been noted in reservoirs after the closure of the fishery, which will lead to a decrease in the efficiency of natural reproduction and further to a decrease in the number of fish. Due to the lack of fishing in the reservoirs of the Tver region, the possibility of catching almost 32,3 thousand tons of fish was lost for 15 years, which in monetary terms amounts to 5,15 billion rubles.

Fluctuations in Cd release from surface-deposited sediment in a river-connected lake following dredging

Some special features of the Azerbaijan river water resources formation have been discussed. A considerable share of the runoff enters the Azerbaijan territory from neighboring territories with the transit rivers. This input value for a year of average water content is 652 m3/s or 20.6 km3. The river runoff which forms directly on the territory of the country is assessed as equal to 328 m3/s or 10.3 km3. As a whole the local river water resources comprises 58% of the surface runoff and 42% groundwater runoff. Total river water resource of Azerbaijan is 735 m3/s or 23.2 km3 for a high-water year and 228 m3/s or 7.2 km3 for a lowwater year. It should be noted that 80 % of the country water resources belong to the Kura River basin and its tributaries, 70 % of this amount are formed on the territories of the neighboring countries. Comparison of the water chemical composition of the different periods shows that it completely reflects the level of anthropogenic load upon the catchment. It has been found that over the past 70 years an obvious trend to the Kura River water content decrease is observed. The global climate change and the Azerbaijan territory aridity create keen necessity of the water resources effective management.

Since the 1970s, artificially stabilized water levels, increased presence of common carp (Cyprinus carpio) and invasion by a cattail hybrid (Typha × glauca) have changed the nesting environment for Western Grebes (Aechmophorus occidentalis) at Delta Marsh, Manitoba. To evaluate the impact of these changes, nest survival rates, causes of nest mortality, wind conditions, locations of nests and vegetation structure at nests in 2009–2010, and chick-adult ratios were compared to similar data for Western Grebes at Delta Marsh from 1973–1974. Apparent nest survival rates were lower in 2009–2010 than 1973–1974, and between low-water years (1973, 2010) and high-water years (1974, 2009). Lower apparent nest survival rates in 2009–2010 (49% in 2009 and 43% in 2010, compared to 46% in 1973 and 84% in 1974), and chick-adult ratios (0.55 in 1973 and 0.88 in 1974, compared to 0.55 in 2009 and 0.39 in 2010) were attributed to increases in destruction of nests primarily by wave action and secondarily by common carp, which were not observed destroying Western Grebe nests in 1973–1974. The replacement of native bulrushes by cattails in Western Grebe nesting habitat may have caused the observed increase in proximity to openwater edge, and this proximity may have increased destruction of nests by waves. Restoring stands of emergent bulrush by varying marsh water levels and reducing carp in the marsh might improve nest survival of Western Grebes.

The study estimates the water and water management balance of the Tobyl River basin in the Kostanay region, Kazakhstan in the context of non-stationary climate and river flow conditions.The research aims to determine the current deficit and surplus of water resources to develop recommendations on regional water supply needs, especially for urban territories and agricultural sectors.Hydrometeorological data from regional monitoring stations were analyzed using probabilistic statistical methods.The Mann-Kendall test is applied to assess long-term trends in river flow.A comprehensive water balance model is developed for the reservoirs of the Tobyl River.The study shows statistically significant upward trends in water consumption at the Tobyl-Kostanay and Tobyl-Grishenka stations from 1972 to 2021.The developed water management balance indicates that in average and high-water years, the Tobyl River reservoirs accumulate water, and low-water years (95% non-exceedance probability) are marked by water shortage.Evaporation accounts for a significant share of water losses in the reservoir system, especially in low-water years.The findings underscore the urgent need for advanced water-saving methods and adaptive water resource management strategies to mitigate the consequences of water shortage, especially in low-water years.To ensure a stable water supply in the region, it is recommended to strengthen the coordination of transboundary water resources use and employ technological solutions.

With the depletion of many commercial fish stocks and an increasing demand for marine protein for human consumption, cephalopods have become more important as a fishery resource. In EU waters, cephalopod stocks are not routinely assessed and exploitation of these species by large-scale fisheries is largely unregulated. For sustainable exploitation, adequate assessment and scientifically-supported management strategies are needed. However, there is still a lack of data on stock status and inadequate knowledge of the life history and ecology of these species. The present review examined more than 200 scientific articles, on life history and ecology of European cephalopods, published since 2013. It describes recent contributions to knowledge in the context of previously identified research priorities, along with recent advances towards sustainable fishing and aquaculture. It also identifies outstanding knowledge gaps. While some priority areas, such as the development of the species identification guides and evaluation of climate change impacts on cephalopods, have seen significant advances, other challenges remain for the future. These include monitoring of the life history traits and fishery status for the main commercially exploited species in the area, implementation of improved species identification methods during scientific surveys and fisheries monitoring, development of tools to identify stock units, and the study of the environmental and anthropogenic impacts on the stocks of cephalopods inhabiting European waters.

We studied a metapopulation of great cormorant (Phalacrocorax carbo) in Iceland, using complete aerial censuses of nests in 25 years during 1975–2015. Age composition was estimated in 1998–2014 by ground surveys in September and February. Brood size was estimated from aerial photographs in 2007–2015.Weather, food, breeding habitat, and density were considered as explanatory variables when examining numerical and distributional changes in the cormorant metapopulation.In 1975–1990 total nest numbers changed little, very low numbers about 1992 were followed by an annual increase of 3.5% in 1994–2015. Total nest numbers were positively correlated with estimates of spawning stocks of cod and saithe and inversely related to the subpolar gyre index (SPG‐I).During the increase in 1994–2015, average colony size at first increased and then declined. Habitat use also changed: the proportion of nests on small rocky islets (skerries) at first declined, from 69% to 44% in 1995–2003 and then increased again to about 58% in 2012–2014. Habitat changes were probably a response to changed patterns of human disturbance.Breeding density, as nests per km2 sea <20 m deep, was rather uniform among five defined regions in 1975–1996. Thereafter, densities became much higher in two sheltered regions with kelp forests and in one mostly exposed region. A second exposed region remained low and in the third nest numbers declined markedly. Thus, carrying capacity was higher in sheltered regions where cormorant breeding had historically been depressed by human disturbance.Brood size varied little among regions but declined with the years from about 2.5 to 1.8.The proportion of juveniles in September (fecundity) declined in 1998–2015 from over 0.4 to 0.3 and was inversely correlated with year and nest numbers, if outlier years were excluded, suggesting resource limitation. Survival of juvenile cormorants in September–February was estimated at 0.471 ± 0.066 SE. Commercial fish stocks and climate indices were not correlated with the proportion of juveniles.Annual survival of adults (breeding and nonbreeding) was estimated from nest counts and age composition 1999–2014, as 0.850 ± 0.026 SE and showed no trend in 1998–2014.We conclude that the metapopulation of cormorants in Iceland was resource‐limited at two levels: fecundity at the regional and winter survival at the total level.

The United Nations Convention on the Law of the Sea created the exclusive economic zone regime, which makes more than 90 per cent of the world’s commercial fish stocks under the national jurisdiction of coastal States. The biological characteristics of fish demonstrate that the long-term sustainability of fisheries can only be achieved through cooperation and coordination among States, especially for the conservation of transboundary fish stocks. However, the ocean may have more than 1,500 transboundary fish stocks, only a limited number are subjected to effective cooperative management. This article provides an overview of the international legal framework on transboundary fisheries and China’s practice on shared stocks and distant water fisheries, and argues that current bilateral fisheries agreements are not sufficient enough to manage transboundary fish stocks and China still has much to do on regulating distant water fisheries.

This article reviews the status of fisheries in the western parts of the North and Middle Caspian Sea in the territory of Dagestan Republic, the Russian Federation. Commercial fish stocks are greatly influenced by changes in the Caspian environment induced by natural (sea level fluctuations, water advection, seabed seismicity) and anthropogenic (regulation of major rivers, pollution, invasive species, etc.) factors, as well as fishery management. Fisheries development in Dagestan is reviewed by: (1) summarizing data on the biological and eco-geographical context of biological productivity; (2) evaluating the current status of stocks of the major commercial fish species in this region and assessing the prospects for their commercial use; (3) analyzing the responses of aquatic biological resources to natural and anthropogenic impacts. A number of recommendations are suggested for establishing sustainable fisheries management in the Western Caspian Region.

The northern part of the Agrakhan Gulf, which is a part of the Tersko-Caspian fishery complex of Dagestan, plays an important role in the formation of stocks of commercial fish species, having abundant spawning, nursery and wintering grounds. The efficiency of natural reproduction of fish is determined by the state of the hydrological and hydrochemical regime in the reservoir, which in recent years in this reservoir can be characterised as unfavourable. Studies carried out in North Agrakhan in the period from 2018 to 2022 have shown negative changes in the structure of ichthyofauna, manifested in a decrease in the number of juveniles of passable, semipassable, freshwater fish species and an increase in tuvodny fish of the lake-river complex. The number of juveniles of passable fish species has decreased almost twofold, kutum stocks have reached a critical level, the prevailing semi-passable fish species, which account for up to half of the total volume of recorded juveniles, are also decreasing, although to a lesser extent. Freshwater fish species are in a depressed state, the number of juvenile fish is decreasing from year to year, and has decreased more than twofold over the 5 years under study. The total number of segolets of low-value fishery lake-river fish species for 5 years increased 2 times and was 37% of the total volume of all fish species. In general, in the northern part of the bay the dominance of fish species in the northern part of the bay has become dominant among passable fish species - redfish, semipassable fish species - bream, freshwater fish species - redfish, lake-river fish species - redfish and crucian carp. Such species as kutum, pikeperch and practically all freshwater species are at the stage of extinction, mainly tench, which was recorded in catches only once.

Introduction. Modern hydrology of the Hadzhibeysky estuary is due to natural and anthropogenic factors and characterized by their intense economic use. Since the beginning of the last century, there was an intense discharge of municipal waters from Odessa (biological treatment plant "North"). This led to a significant increase in the levels of water in the estuary, which threatened to destroy the dam that separates the estuary from the sea, with the possible flooding of residential areas and enterprises of the Peresip area, as well as the road, on the dam, especially in disastrously high water years. Purpose. The purpose problems – are estimation of filling the closed estuaries-reservoirs in north-west area of the Black sea and long–term forecasting of their condition during the spring period of year. The first task – an analysis of conditions of the Hadzhibeysky estuary in the presence of an exceptional spring flood and rain floods of exceedance probability (P = 1%). The second task – is to develop a methodology for the long-term forecasting of filling of the Hadzhibeysky estuary during the spring flood, which is the most abundant phase in the hydrological regime into the territory.&#x0D; Results. For the first time, the possibility of assessing the filling degree surface water from melting snow and rainfall when the estimated probability of exceeding P=1% in the closed estuaries-reservoirs of the Black Sea areas. The method of the long-term forecast of surface water during the spring period for the closed estuaries was substantiated. Typification of spring floods in accordance with their water content according to the model – discriminant function DF, which takes account of the complex of factors having an influence upon conditions of spring flood formation. Setting the probability of occurrence of the forecasting flow layers in the long-term period are implemented.&#x0D; Conclusion. This method allows risk assessment for sustainable land – and water use planning within the Black Sea estuaries. The method of the long-term forecast was realized by the author in operational work at the Hydrometeorological Center of the Black and Azov Seas.

The problem of assessment of sea level rise impact on the hydrological regime and morphological structure of river deltas is discussed. Studies of the response of river deltas, which are among the most vulnerable natural objects, to the sea level rise has become urgent because of the global climate warming and the associated acceleration of the World Ocean level rise. Methods are described that can be used for the analysis, calculation, and prediction of sea level rise impact on submergence of deltas, propagation of backwater from the sea tides, surges, and salt seawater intrusion. Special emphasis is given to channel processes in delta branches, which accompany sea level rise, as well as to delta coastline erosion and flow redistribution among branches. In the course of research, due consideration was taken of the experience gained in studying the response of river deltas on the Caspian Sea coasts to the recent considerable level rise in this water body.

Many experimental evolution studies have shown the ability of model animal species, such as Drosophila melanogaster, to adapt quickly to various adverse conditions such as unfavorable growth medium. Here we performed an evolutionary experiment in which some D. melanogaster lines were reared on a growth medium with two regimes of high NaCl concentration (4% and 7%), while the others were reared on the standard (favourable) medium. We evaluated the reproductive efficiency of experimental lines on the same two different unfavourable growth mediums five years after the experiment started. Our tests confirmed that the lines reared on the salty substrate became more tolerant to high NaCl concentration, with lines reared on 7% being overall better than lines reared on 4%, especially when tested on 7% medium. Moreover, we found that pre-inoculation of the high salt medium with homogenized salt-tolerant flies tended to improve reproductive efficiency on this medium. Besides, we found out that individual laboratory line history is also an important factor that affect evolutionary experiment results. Finally, we show that general adaptive traits (overall number of mature offsprings and their development speed) can change linearly (number of mature offsprings) and non-linearly (development speed) when fruit flies progressively adapt to growing NaCl concentration (0 → 4% → 7%).

The Hudson River Foundation convened a conference to evaluate evidence pertaining to the roles played by acid deposition and stream acidification in the decline of anadromous fish populations along the Atlantic coastal plain. The stimuli for the conference were that (1) some populations of Atlantic salmon, American shad, hickory shad, alewives, blueback herring and striped bass as well as a few species resident in coastal streams (yellow perch and white perch) are in a state of severe decline along portions of the east coast of North America; (2) several of these species have declined more or less simultaneously since about 1970; and (3) severe episodic pH depressions are observed in some streams of the Chesapeake Bay system. For example, the pH of Lyons Creek decreased from 7.0 to 5.9 in 1 hr during a rain event, returning to 7.0 a day later. After discussing several possible mechanisms for these observations, the conferees agreed that a combination of factors including stream and river acidification, toxic metals and organic compounds, eutrophication and overfishing appears to be contributing to the reduction in fish stocks. The essential point resulting from the conference is that the acid deposition hypotheses for stream acidification and declines of anadromous fish populations, a potential mechanism that has received very little attention heretofore, was shown to be viable for these coastal areas. Specific recommendations for research were agreed upon by the conferees.

This study characterized the profile of fishing and fishing communities, as well as the consequences that the Fundão dam break disaster in Mariana, Minas Gerais, had on artisanal fishing in the Rio Doce Basin. A total of 1,998 semi-structured questionnaires were applied in 42 municipalities along the Rio Doce and its mouth. As a result, the profile indicates the predominance of men, with an average age of 49 years, with extensive experience in fishing activities and primary education level. Small-scale fishery often occurs onshore, especially in the upper and middle reaches of the Rio Doce. Regarding the main consequences of the disaster, there is evidence of abandonment of fishing activities, especially in the upper and middle reaches of the Rio Doce, and a reduction in income. Pollution and reduction of fish stocks appear as some of the main problems, and among the expectations of local actors is the desire to return to fishing activities. Finally, it is evident that until now, fishing communities still suffer from its consequences, and there has been no recovery from fishing activities. These results are important for reparation actions to achieve their goal.