Biological characteristic of the bream abramis brama l. In the Dnieper-bug mouth region

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Biological characteristic of the bream abramis brama l. In the Dnieper-bug mouth region

Kornienko V.O. - Candidate of Agricultural Sciences,

Olifirenko V.V. - Candidate of Veterinary Medicine,

Rozhkov V.V. - Candidate of Agricultural Science, Associate Professor at the Department of Aquatic Bioresources and Aquaculture, Dnipro State Agrarian and Economic University

Abstract

The effective functioning and development of the fishing industry of Ukraine in the economic space is determined not only by quantitative indicators, but also by the peculiarities of the economic relations formed at the end of the past - the beginning of the present century. The basis of the raw material base of the fishing industry of Ukraine, including the Kherson region, at the end of the 20th century was formed mainly due to catches of fish and seafood and, to a lesser extent, the products of intensive fish farming. At the same time, the fisheries of the Kherson region over the past decade have seen a steady decline in production and processes of reducing its potential, including the aging of the technical base, increasing resource and financial imbalances, leading to a decline in production. The situation is exacerbated by the increasing anthropogenic pressure on aquatic ecosystems, which has caused a sharp decline in fish catches of major industrial categories, additionally a few rare species have disappeared from industrial statistics. Natural fish populations adequately respond to the situation through adaptive reactions in the form of changes in the nature of ichthyologic mass formation, age structure, in productive indicators of species.

These studies highlight the issue of the state of productive capabilities of the local stock of bream of the Dnieper-Bug estuary. The initial data for the tasks are the results of field research conducted in the waters of the Dnieper-Bug estuary in 2014-2018 in the framework of the investigations of the Educational and Scientific Laboratory "Prospects of Aquaculture" of the Kherson State Agrarian and Economic University. Abramis brama L. bream of different ages were selected as the object of research.

Key words: Dnieper-Bug mouth region, bream, productivity indicators, fertility, catches, anthropogenic load.

Корнієнко В.О., Оліфіренко В.В., Рожков В.В. Біологічна характеристика ляща Abramis Brama l. у Дніпровсько-Бузькому гирлі

Ефективне функціонування і розвиток рибної галузі України в економічному просторі визначається не тільки кількісними показниками, але й особливостями сформованих економічних відносин у кінці минулого - на початку нинішнього століття. Основа сировинної бази рибної промисловості України, зокрема Херсонської області, у кінці ХХ століття формувалася переважно за рахунок уловів риби і морепродуктів і меншою мірою - продукції інтенсивного рибництва. Водночас у рибному господарстві Херсонської області за останнє десятиріччя спостерігається стійкий спад виробництва і відбуваються процеси зниження його потенціалу, зокрема старіння технічної бази; посилюються ресурсна і фінансова незбалансованість, що призводить до занепаду виробництва. Ситуація поглиблюється посиленням антропогенного навантаження на водні екосистеми, що спричинило різке падіння уловів риби основних промислових категорій, а рідкісні і нечисленні види взагалі зникли із промислової статистики. Природні популяції риб адекватно реагують на ситуацію через пристосувальні реакції у вигляді змін у характері формування іхтіомаси, у віковій структурі, продуктивних показниках видів.

У дослідженні висвітлено питання про стан продуктивних можливостей локального стада ляща Дніпровсько-Бузької гирлової області. Вихідними даними для виконання завдань роботи є результати польових досліджень, що здійснювалися протягом 2014-2018 рр. в акваторії Дніпровсько-Бузької гирлової області у межах теми Навчально-наукової лабораторії "Перспективи аквакультури" Херсонського державного аграрно-економічного університету. Об'єктом дослідження обрано різновікові особини ляща Abramis brama L.

Проведений аналіз продуктивних здібностей самиць ляща показав пригнічений стан популяції у межах акваторії, яка була місцем досліджень. Абсолютна індивідуальна плодючість самиць ляща залежно від віку коливалася в межах від 86,62 до 288,69 тис. ікринок, її мінімальне значення відмічено для 4-річних самиць за середньої довжини тіла 30,5 см і маси 647,5 г, максимальне значення - для 11-річних самиць за довжиною тіла 48,9 см і масою 2047,1 г. Водночас за п'ять років спостережень плодючість самиць ляща за окремими віковими групами зменшилася на 8,2-12,8%. Натомість порівняно з минулим століттям у сучасності величина абсолютної індивідуальної плодючості самиць ляща за всіма віковими групами зменшилася на 6,1-28,2%. Значні відмінності за величиною плодючості спостерігались як у молодших за віком самиць, так і самиць найстаршого віку, що яскраво вказує на погіршення репродуктивних здібностей стада внаслідок посилення антропогенного тиску на популяцію ляща.

Результати досліджень суттєво поглиблюють відомості про сучасний біологічний стан промислового стада ляща у Дніпровсько-Бузькій гирловій області. productive bream herd

Ключові слова: Дніпровсько-Бузька гирлова область, лящ, продуктивні показники, плодючість, улови, антропогенне навантаження.

Formulation of the problem. In the context of the economic crisis, intensive fish farming requires significant costs associated with high prices for artificial feed, fertilizers and energy. In addition, Ukraine has a large area of continental reservoirs, reaching more than 1 million hectares, much of which is currently used very carelessly for fisheries purposes. This is due to inefficient management, ignoring the achievements and recommendations of fisheries science, lack or insufficient amount of fish stocking material of valuable fish species for the formation of highly productive ichthyo-cenoses [1; 2; 3].

A particularly difficult situation is observed in large open and semi-closed waters - estuaries, large reservoirs, lakes. These hydroecosystems have an incredibly significant bioproductive potential, represented by producers and consumers of different trophic levels, and the formed industrial ichthyofauna [4, 5]. However, at the beginning of the XXI century, the situation changed dramatically for the worse. A sharp decrease in the stock of planting material of valuable industrial species against the background of virtually uncontrolled industrial fishing, low efficiency of fisheries and reclamation measures, caused a sharp decline in stocks of major industrial fish species within these waters [6; 7].

Analysis of recent research and publications. When studying the main biological indicators of an industrial herd, it is necessary to take into account the peculiarities of its structure. The structure of the herd is specific to the species and its individual local groups, it is a species and population property that reflects the nature of the relationship of individual populations with the environment [8]. In recent years, industrial populations of natural and transformed waters of Ukraine are under increasing pressure of environmental factors of anthropogenic nature [2; 6; 10]. The negative impact of these factors causes a sharp reduction in the number of populations and individual local herds of almost all valuable industrial fish species, including the Dnieper bream. Populations respond adequately to the situation through adaptive responses in the form of changes in growth, fertility, etc. [8]. A number of authors have shown that changes in the dynamic and functional indicators of ichthyocenoses can serve as macrocharacteristics of aquatic ecosystems, and the assessment of the main factors of formation and operation of industrial fish stocks - the basis for forecasting and regulation of fisheries [11; 12].

Changes in the biological state of the Dnieper bream herd due to the deterioration of the ichthyopathological situation have been sufficiently considered. Thus, it was found that the muscles of bream infested with Lamblia intestinalis contain less protein, fat, ash, calcium and phosphorus and have lower caloric content compared to healthy fish [18; 19]. Infection of fish L. intestinalis leads to a decrease in body weight of fish (without internal organs), to the loss of the edible part of the body of fish. In addition, the quality of muscles deteriorates compared to healthy fish, they increase the amount of moisture, reduce dry matter content, amount of fat and calories [19; 20-22]. There are slight changes in the chemical composition of the muscles of bream infected with plero- cercoid L. intestinalis (water content, proteins, bicarbonates, lipids), compared with the high level of their energy reserves (such as triglycerides), which indicates the limited negative impact of L. intestinalis on physiological lentil loom.

Research methods. The research was guided by the principles of bioethics. The studies were carried out in accordance with the European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes ETS No. 123 and approved by the Science Council of the Kherson State agrarian and economic University. The initial data for the tasks are the results of their own field ichthyological research, which was carried out during 2014-2018 directly on water bodies in the research of the Educational and Scientific Laboratory "Prospects of Aquaculture" of the Kherson State Agrarian and Economic University. The object of the study were selected bream of different ages Abramis brama L., which belong to the local herd that lives within the waters of the Dnieper-Bug estuary. During the works, ichthyological samples were taken from catches of shuttered nets with an eye of 40-75 mm, livers with an eye of 30-40 mm, river seines.

The samples were subjected to processing, during which samples were taken for in-depth ichthyological analysis [23]. The sex of individuals was determined by the presence of secondary sexual characteristics, but for a more reliable analysis preferred the opening of the abdominal cavity. Absolute individual fertility was calculated by the weight method, and relative individual - as the ratio of absolute fertility to body weight of fish without viscera and body length [23].

Data are presented as mean values and standard error (x ± SE). Statistical analysis was performed by means of analysis of variance (one-way ANOVA). A value of P <0.05 was considered statistically significant. Analysis of the variance of the influence of technological and environmental factors on the growth of larvae was carried out using the.

In this case, the catch can be compensated by the regulatory mechanisms of the population, i.e. when the catch seems to be an element of the environment of the species. If the catch maintains a similar intensity and spawning and development conditions and the youth are not disturbed, the population can exist for many years. In populations of intensively caught commercial fish, the growth rate is higher and fertility is higher. However, in all fish populations with increasing fishing intensity, positive reactions are observed only to a certain extent. With a further increase in fishing intensity, the regulatory mechanisms of the population are disrupted, and it ceases to respond to further thinning of the herd, the main biological indicators deteriorate. In our studies, the productive properties of females of the Lower Dnieper herd of bream varied slightly over the years (Table 1).