نوع مقاله : مقاله پژوهشی
نویسندگان
1 سازمان تحقیقات، آموزش و ترویج کشاورزی، موسسه تحقیقات علوم شیلاتی کشور، پژوهشکده آبزی پروری آبهای داخلی، بندر انزلی، گیلان
2 مرکز بازسازی و حفاظت از ذخایر ژنتیکی ماهیان شهید انصاری رشت، اداره کل شیلات استان گیلان، گیلان
3 سازمان تحقیقات، آموزش و ترویج کشاورزی، موسسه تحقیقات علوم شیلاتی کشور، تهران، تهران
چکیده
کلیدواژه‌ها
عنوان مقاله [English]
نویسندگان [English]
Introduction: The Kutum (Rutilus frisii), a member of the Cyprinidae family, is a unique species of bony fish native to the Iranian shores of the Caspian Sea. It has significant potential as a suitable candidate for introduction to aquaculture industry in Iran. Stocking density is a critical factor in fish pond management, as it often negatively impacts fish growth and welfare in aquatic environments. The negative impact of stocking density on growth performance is primarily due to the induction of stress in fish, leading to reduced feeding and growth rates. Among the most significant reasons for the occurrence of stress in this context are the interactions between fish, competition for food resources, and the habitat required. Therefore, determining the optimal stocking density for Kutum during the grow-out phase in earthen ponds is essential for enhancing productivity and maximizing economic profitability.
Materials and Methods: In this research, the growth performance and survival rate of Kutum were evaluated in the grow-out stage with an average weight of 60.89 ± 7.21 g in two densities of 5600 and 8000 fish per hectare in 700 m2 earthen ponds during the 3-month period. The fish were fed to satiation with extruded feed twice daily at 9:00 AM and 1:00 PM. The physical and chemical parameters of the water, including temperature, dissolved oxygen, nitrite, nitrate, ammonia, phosphate, and bicarbonate were measured using the AOAC (2023) method. Plankton and benthos sampling and identifying were conducted seasonally during summer and autumn from earthen ponds based on standard methods. To evaluate growth trends based on experimental treatments, Kutum were biometrically assessed. The length and weight of 50 fish were measured each time using a biometric board and a scale with an accuracy of 0.01 g. The growth indices and survival rate were calculated by reference formulas. For data analysis, One-way analysis of variance (ANOVA) was used. Additionally, Duncan's multiple range test was employed to examine the significance of mean differences among experimental treatments. Data evaluation was performed using SPSS software.
Results and Discussion: The results showed that the growth performance of Kutum decreased significantly by the elevation of density (P≤0.01). The average percentages of weight gain in the first and second treatments were 248.62 ± 102.04 and 115.58 ± 49.51 g and the average food conversion ratio were 2.15 ± 0.92 and 4.23 ± 1.64, respectively, and the difference between the treatments was significant (P≤0.01). Also, the difference between the 1st and 2nd treatments in the retention rate of the reared fish at the end of the rearing period was not significant and it was 80.58 ± 2.43 and 76.07 ± 3.51, respectively (P>0.01). The amount of final fish crop in treatment 1 was higher than in treatment 2; 1646.51 ± 109.55 and 1589.91 ± 88.94 kg/ha, respectively, but the difference between the treatments was not significant. The results of our study showed that the average data for the earthen ponds during the farming period fell within the standard range for warm-water fish, and this indicates the suitable condition of the measured parameters during various stages of farming throughout the production period. Higher stocking density led to a reduction in the diversity and abundance of live food (benthos and zooplankton) in the pond due to faster consumption by the fish within a shorter period during the farming cycle. Our study has shown that fish at higher densities are exposed to increased competition for food and space, leading to physiological stress. This can resulted in reduced growth indices, feeding efficiency, feed conversion efficiency, product yield, and survival rates. The results of our study align with findings from other researchers regarding the effects of stocking density on the performance of other aquatic species.
Conclusion: In general, this study concluded that high stocking density has significant effects on the growth, survival, and production yield of Kutum during the grow-out stage. Therefore, it is recommend to stock 5,600 Kutum per hectare in 700-m2 earthen ponds to achieve higher production with optimal performance.
کلیدواژه‌ها [English]
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