Patimar Rahman, Badraghi Behrouz**, Seifi Taghi***
*, **Gonbad Institutes of Higher Education, Gorgan University of Agricultural Sciences
and Natural Resources, Gonbad, Iran, firstname.lastname@example.org,
***Department of Fisheries, Faculty of Fisheries and Natural Resources,
Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
НЕКОТОРЫЕ АСПЕКТЫ ЖИЗНЕННОГО ЦИКЛА ТРЁХИГЛОЙ КОЛЮШКИGASTEROSTEUSACULEAUSВ РЕКЕ СИХРУД
(ЮЖНЫЙ ПРИКАСПИЙ – ИРАН)
Р. Патимар, Б. Бадрахи, Т. Сейфи
*, **Институт высшего образования Гонбада, Горганский университет сельскохозяйственных наук и природных ресурсов, Гонбад, Иран, email@example.com,
***Кафедра рыболовства, Факультет рыболовства и природных ресурсов, Горганский университет сельскохозяйственных наук и природных ресурсов, Горган, Иран
The Gasterosteidae family has 2 species in Iran; ninespine stickleback Pungitius platygaster (Kessler, 1859) is native to Iran and threespine stickleback Gasterosteus aculeatus Linnaeus, 1758 appears to be of a “marine” form, which reported as an introduction to Iran by Abdoli (1993) and Coad and Abdoli (1993). In the range distribution of the fish in northern hemisphere, Iranian coast of Caspian Sea forms the southern limit of its distribution (Coad, Abdoli, 1993). To our knowledge, no detailed studies of the species have been exclusively conducted in the southern Caspian basin. We hypothesized that the south Caspian basin may contribute to habitat-specific variation in life history traits of threespine stickleback. Therefore, for a better understanding of life history of threespine stickleback from southeastern Caspian basin, this paper attempts to represent of first detailed information on this fish .
The present study was carried out in the mouth of SiahroudRiver which is situated at the south of Caspian Sea. It is a type of small stream rising on the humid north slope of the Elburz Mountains (MazanderanProvince). Sampling on the basis of once per month, was carried out using beach sein from November 2006 to July 2007. In the laboratory, total length was measured to the nearest 1 mm for all fish sampled. Total weight and weight of gonads were recorded with an electronic analytical balance to the nearest 0,01g. The age was determined from opercula taken from both sides. Sex was determined by examination of the gonad tissue either with eye or with the aid of a binocular. An analysis of co-variance (ANCOVA) was performed to test significance differences in weight-length relationships between sexes. The overall sex ratio was assessed using Chi square test (Zar, 1984). Comparison of GSI values during reproductive period and its temporal variation in each sex carried out by analysis of variance (ANOVA). Statistical analyses were performed with SPSS 11,5 software package and a significant level of 0,05 was accepted.
Of the collected specimens, males ranged from 45 to 70 mm and 1,10 to 3,58 g, while females ranging from 45 to 98 mm and 0,96 to 4,02 g. Aging revealed that the older ages recorded were 3+ for both sexes. In the population, observed length-at-age were different between sexes, females were longer and heavier than males (ANCOVA, F=141,08, P<0,05). The most frequent size classes in the samples were 57–58 mm for males and 63–64 mm for females. Males were absent in the length classes larger than 69–70 mm. Length-weight relationship evaluated by using the lengths and weights were found significant with the high regression coefficient. The b-values of considered groups imply that the body shape of the fish displays negative allometric form (t-test, tmale=21,80, tfemale=7,17, tpopulation=13,01, p<0,05). All of individuals were sexed. Even though the overall ratio of males to females was 1:1,19, Chi-square analysis showed no significant differences from the ration 1:1 (χ2=3,02, p>0,05). An unequal sex ratio was observed among the length groups, males were dominant in length groups ranged from 55 to 60.
Significant changes were obtained in the temporal variation of GSI (ANOVA, Ffemale=21,09, Fmale=5,18, p<0,05). The GSI values of males were significantly lower than those of females (ANOVA, F=281,03, p<0,05). The highest average recorded values of GSI were in April for males and in May for females; 1,67±1,05 (SD) for males and 14,31±8,42 (SD) for females. Following the seasonal cycle of GSI, the reproductive period is extended from April to June when GSI is considerably higher.
Two kinds of eggs were found in the ovary, small white opaque eggs measuring between 0,32 and 0,66 mm with a mean value of 0,435±0,076, and large yolk-filled eggs ranged from 0,60 to 2,15mm with a mean value of 1,161±0,292 (SD). For Caspian stickleback ova diameter, both small and large ova, was negatively correlated to fish size (length or weight), an increase in female size (total length or/and weight) implied a decrease of ova diameter.
Total number of small eggs ranged from 311 to 4709 with a mean value of 1512,94±904,19 (SD), and of large yolk-filled eggs from 128 to 885 with a mean value of 454,32±195,23. The absolute fecundity ranged from a minimum value of 235 in a 1+ years old female weighing 1,96 g to a maximum value of 5460 in a 3+ years aged female weighing 2,56 g. The mean value of absolute fecundity was 1837,34±1028,96 (SD). For the fish in the southern Caspian Sea, both absolute and relative fecundities were positively correlated to fish size (length or weight).
Fecundity relative to total weight (g) fluctuated from 84,42 to 2441,61 eggs/g, with a mean value of 799,30±374,99 (SD), and relative to total length (mm) from 2,36 to 84 eggs/mm, with a mean value of 31,72±15,53 (SD). The relationships of relative fecundity with body size (either to length or weight) were also found to be statistically significant, but with low correlation.
In the present study, differences between males and females in the LWR are explained by the differences in size distribution of the two sexes as a consequence of inter-sexual differences in growth. The b-values estimated in the studied population are different from those cited by Wootton (1984) and Crivelly and Britton (1987). This reflects a change in body form with population, which is itself probably an effect of different environmental conditions influencing as local selective pressure on fish condition. In the SiahroudRiver, during this study, sex ratio was unlike that reported by (Wootton, 1984). In fact, the predominance of females is common in G. aculeatus populations and the differences in sex are highly significant throughout its range distribution (Wootton, 1984). Balanced sex ratio in the river is probably either the consequence of same survival rate and longevity of the sexes or the same endurance of the sexes to environmental variability.
Based on the highest average recorded GSI, it is evident; the proportionate investment by fish in the reproduction is much higher in females than in males. In the river, comparison with other southern Caspian fishes, G. aculeatus has an extended breeding season (3 months). It is reported that the spawning season of the fish appears to vary with locality over the wide range of this species (Coad, Power, 1973).
In the population under consideration in this study, the mean large egg size (1,16 mm) is considerably smaller than that of recorded in other populations, and also the degree of size variability (SD=0,29 mm) exhibited by the Siahroud river population is greater. This variability coupled with small size of ova could be considered as maternally induced heterogeneity in offspring of a migratory population, a reproductive strategy by the population of the three-spined stickleback in the river.
A wide range of values for the fecundity of the three-spined stickleback has appeared in the literature. The comparison of egg production by female is complicated because of the existence of two forms of the stickleback, the anadromus trachurus form with high absolute fecundity, and the freshwater leiurus form which has considerably less fecundity. Considering the absolute fecundity, the Sihroud river population is far more fecund, suggests being a trachurus type of the fish.
It can be concluded that the life history patterns of this species varied relatively to the habitat to which they exposed, showing a wide range of adaptations over its geographical range. The variations relating to growth and reproduction may be interpreted as phenotypic plasticity and adaptation to local environmental conditions.
Zoocenosis — 2009
Біорізноманіття та роль тварин в екосистемах: Матеріали V Міжнародної наукової конференції. – Дніпропетровськ: Ліра, 2009. – С. 119-121.