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Ribogospod. nauka Ukr., 2025; 4(74):63-83
DOI: https://doi.org/10.61976/fsu2025.04.063
UDC 597.556.35(26)

Main morpho-biological characteristics of the European flounder (Platichthys flesus Linnaeus, 1785) of the Shabolatski estuary in the period from 1980 to 2020

P. Shekk, This email address is being protected from spambots. You need JavaScript enabled to view it. , ORCID ID 0000-0002-2789-0854, I. I. Mechnikov Odesa National University, Odesa
D. Shumarin, This email address is being protected from spambots. You need JavaScript enabled to view it. , I. I. Mechnikov Odesa National University, Odesa

Purpose. Study of changes in the main morpho-biological characteristics of the European flounder P. flesus of the Shabolatsky lagoon for the period from 1980 to 2020.

Methodology. The study was conducted in 1980–2020 in different seasons of the year. The material for ichthyological studies were representative samples (25-50 fish) taken from commercial and control fishing gears.

Generally accepted methods of ichthyological studies were used. The sex, fecundity, composition of diets and the ratio of individual food components were determined. The age of fish was determined using otoliths. Condition factor was calculated based on actual data. Microsoft Excel was used for statistical data processing.

Findings. In the 1970s and 1980s, the European flounder of the Shabolatsky lagoon was characterized by high growth and condition factor. After the ecological disaster in 1993, the size, weight and condition factor of European flounder in all age groups significantly decreased. In the following period, the length and weight of the flounder population in the lagoon gradually increased, but they never reached those of the previous period. The variability of the length-weight composition of the population increased, and the condition factor of fish decreased. All these changes directly depended on the state of the feed supply, which caused changes in the composition of the diets of European flounder. After 1993, the diet of flounder in the lagoon changed.

Males in the lagoon reached sexual maturity in the second year of life, females in the third or fourth.

In the spring, mass migrations of age-0+ European flounder were observed from the sea to the lagoon, and in early autumn, sexually mature fish left the lagoon to the sea.  Systematic migrations of the European flounder suggest that today there is no separate (isolated) lagoon population of flounder, and the population of the Shabolatsky lagoon is a combination of marine and lagoon forms of flounder, the ecological and biological features of which are formed under the influence of the peculiarities of the lagoon ecosystem.

Originality. For the first time since 1980, the results of a study of the European flounder from the Shabolatsky lagoon are presented. A retrospective analysis of changes in the size, weight, age, and sex composition of the population was carried out. This assessment of condition factor, nutritional characteristics, and fecundity of flounder of different size and age groups. 

It is assumed that the lagoon population of the European flounder from the Shabolatsky lagoon today represents a combination of marine and lagoon forms of flounder, the ecological and biological features of which are formed mainly under the combined influence of environmental factors.

Practical Value. The presented ecological and biological characteristics of the European flounder will allow us to objectively assess the current state of the glossa population in the lagoon and can be used to optimize fishing and the technology of artificial reproduction and cultivation of this object in mariculture.

Keywords: P. flesus, Shabolatsky lagoon, growth, fattening, diet, fecundity, population structure, age, sex.

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