Dependence of the round goby’S (neogobius melanostomus) population structure on ecological conditions




Дата канвертавання24.04.2016
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DEPENDENCE OF THE ROUND GOBY’S

(NEOGOBIUS MELANOSTOMUS) POPULATION STRUCTURE

ON ECOLOGICAL CONDITIONS
Maria Tkachenko

Tavria State Agrotechnological University, Melitopol, Ukraine

Research advisor – Yulia Polikarpova
The study of ecological patterns of population structure has significant value nowadays. One may differ from another in the level of development, size, age, and other characteristics. Ecological characteristics and hydrological conditions cause changes in the population structure. Changes of the degree and nature of the population is an essential feature that reveals the dynamics of a population. In other words, it is an adequate response to different ecological characteristics and hydrological conditions.

This is relevant for such an everybiont species as round goby (N. melanostomus) species. Since the round gobies don’t migrate on long distances and are adherent to certain areas of the sea, their dependence on environmental conditions is essential.

The objective of our research is to analyze differences in the population structure of the round goby (size, age and sex structures) under changing ecological conditions.
The family of Gobiidae is one of the largest polymorphic groups of fish. It includes 850 species that inhabit shallow areas of tropical and temperate seas and fresh water. There are five commercial species: the round goby (Neogobius melanostomus) (Pallas, 1814), the monkey goby (Neogobius fluviatilis), the toad goby (Mesogobius batrachocephalus), the syrman goby (Neogobius syrman), the grass goby (Zosterisessor ophiocephalus).

It should be mentioned that in the Azov Sea region the round goby is an important food resource. The volume of the gobies caught in the Azov Sea in comparison with other fish is shown on figure 1 (Fig.1). The total amount of their catch in the Azov Sea for the period of nine years (2000 – 2008) is about 7521.10 tons.

Study of differences in population structure is important for fisheries, because changes of environmental conditions often lead to deterioration of fishing, and consequently the decrease of the region’s economic component.

Proportion of the gobies catches in the Azov Sea has been shown in the dynamics of their catch for nine years (Fig.2). Among them the round goby amounts the largest number of catches (about 90%). Thus, the question arises about the round goby’s ability to adapt to changing habitats.

At the current stage of our research we have analyzed individuals from two basins of the Azov Sea (the first near Kirillovka village – 10 km from the coast, the second in the lower part of the Utliutsky firth – 100 m from the coast). Factual material was collected in July 2010.

In the Utlyutskyy firth the number of males caught dominates over females, in the Azov Sea there is the same amount of them (Tab. 1). The average size of males from Utlyutskyy firth is 2,66 cm larger than females, but in the Azov Sea females are 1,1 cm larger than males.


Table 1. Comparative characteristics of the catching structure of the Azov Sea and Utlyutskyy firth populations of the round goby

Utlyutskyy firth

The Azov Sea




amount

min

max

aver

mist

amount

min

max

aver

mist

♂♂

72

7,00

15,70

12,48

± 0,16

22

5,70

7,80

6,80

± 0,16

♀♀

17

6,00

13,00

9,82

± 0,52

22

6,07

11,80

7,90

± 0,29

♂♀

89

6,00

15,70

11,97

± 0,19

45

5,70

11,80

7,38

± 0,18

So, there is a substantial increase in the number of females compared to males, as well as their size in Utlyutskyy firth, and vice versa, the number is equal for both sexes and females dominate in the Azov Sea. This probably happens due to the fact that since Utlyutskyy firth is a regular reservoir for feeding because it has good forage base, the round gobies come for feeding grounds to Utlyutskyy firth and for spawning to the Azov Sea.

Thus, we can conclude that, depending on the features of the biological species differences in the structures of populations in water with the different ecologically conditions can be observed. The differences of environmental conditions is a prerequisite for changes in the population structure.


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