Replacement of fish oil with canola vegetable oil-based diets on growth and survival of the Caspian salmon (Salmo trutta caspius) fry

This study was conducted to evaluate the effect of different levels of canola oil on growth performance and survival of Caspian salmon fry (Salmo trutta caspius) during replacement with canola oil over a period of 60 days. 180 fish fries (4.25 ± 0.68 g) with a density of 15 were distributed and introduced to 300 liter fiberglass tubs. For this purpose, 4 treatments with 3 duplication, diets including 100% fish oil, 100% canola oil, 50% fish oil and 50% canola oil, 70% fish oil and 30% canola oil (with the same protein and fat levels of 43 and 14%, respectively) were applied. The results showed that the highest weight (26.46 g), final length (13.46 cm) and specific growth rate (2.97%) were belonging to the treatment containing 50% fish oil and 50% canola oil which showed a significant difference with other treatments (p≥0.05). Moreover, the lowest value of feed conversion ratio (1.41) and the highest amount of status factor (0.09 ± 1.08) were also related to treatment 3, but these differences were not statistically significant (p≥0.05). The highest protein efficiency coefficient of 2.37 was related to the treatment containing a mixture of 70% fish oil and 30% canola oil, which showed a significant difference with other treatments (p≤0.05). The survival rate among all treatments was 100% (no losses). Based on the results, it can be concluded that the replacement of part of fish oil with canola oil (50% fish oil with 50% canola oil) in the diet of Caspian salmon not only has no negative impact on growth factors and survival of Caspian salmon, but also it will improve these factors and can decrease costs by reducing the length of the culture period.