Document Type : Research Paper
Authors
1
1- Aquatics and Fisheries Research Department, Mirzakochek Khan Fisheries Science Education Unit, Guilan Research Center, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran
2
2- Research Department of Experimental Sciences Education, General Directorate of Education, Gilan Province, Bint Al-Hoda Sadr Educational Campus, Rasht, Iran
10.22124/japb.2025.29778.1562
Abstract
This study was conducted to evaluate the effect of heavy metal zinc on growth, nutrition, survival rate, and some hematological parameters of rainbow trout (Oncorhynchus mykiss) at Mirza Kuchak Khan Higher Education Center in Rasht and the Shalizar Novin integrated farm in Keysam, Astaneh Ashrafieh in the spring of 2019. A total of 540 trout with an average weight of 20.19±2.45 grams were divided into 4 treatments and 3 replications (45 fish in each replication). Treatments 1, 2, 3 and 4 were reared with identical diets and water containing 0%, 5%, 25% and 50% of the LC5096h concentration (9.4 mg/L) of zinc metal for 8 weeks, respectively. The results showed that the final weight of rainbow trout in treatment 1, treatment 2, treatment 3 and treatment 4 was 53.20, 55.90, 50.55 and 48.71 grams respectively. The body length of rainbow trout in treatments 1 to 4 was 16.8, 17.7, 16.3 and 16.2 cm respectively. The highest body weight and length were observed in treatment 2, which was significantly different from treatments 3 and 4 (P≤0.05) but not significantly different from treatment 1 (P≥0.05). There was no significant difference in the final weight and length of fry between treatments 25% and 50% (P≥0.05). Adding zinc to the water for rainbow trout fingerlings had a significant effect on reducing the survival rate (P≤0.05). The results of the effect of zinc on fish red blood cells showed that the number of red blood cells in the experimental treatments of 25% and 50% zinc concentration had a decreasing trend compared to the 0% treatment (P≥0.05). Regarding white blood cells in the experimental treatments of 25% and 50% zinc concentration, a significant decrease and difference was observed compared to the 0% treatment (P≤0.05). This rate had a decreasing trend in the two treatments of 25% and 50%, but in the case of the 5% treatment, both red blood cells and white blood cells increased compared to the 0%, 25%, and 50% treatments (P≤0.05). In this study, although zinc had a positive effect on growth variables and blood indices in the 5% treatment, there was a significant difference between the 25% and 50% treatments in the number of blood factors including red blood cells (RBC), hematocrit (HCT), hemoglobin level, and blood indices in rainbow trout samples with 0% and 5% treatments (P≤0.05). Also, all growth variables in the 25% and 50% zinc treatments had a significant difference with the 0% and 5% treatments (P≤0.05). As a general conclusion, it can be stated that exposure of rainbow trout to heavy metal zinc at a level above 5% concentration of h LC5096h caused changes in the amount of blood indices, growth and survival rate of this fish. Therefore, measuring this parameter is essential for monitoring water quality for economic, healthy and hygienic production of this fish.
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