1- Department of Fisheries, Faculty of Natural Resources, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran 2- Department of marine and fisheries sciences, Faculty of Natural Resources and Environment, Tehran North Branch, Islamic Azad University Tehran, Iran , mousavi.nadushan@gmail.com 3- Farzanegan 4 High School, National Organization for Development of Exceptional Talents (NODET/SAMTAD), Tehran, Iran
Abstract: (84 Views)
The Molly fish (Poecilia sphenops) is a significant species in the ornamental fish industry, highly valued for its phenotypic diversity, environmental adaptability, and ease of propagation. In ornamental aquaculture, growth performance and skin coloration are two critical quality parameters, both of which are strongly influenced by dietary intake. Natural pigment sources, such as astaxanthin and Spirulina algae, are frequently utilized as functional feed additives to enhance these traits. This study aimed to evaluate the effects of dietary astaxanthin and Spirulina supplementation on the growth performance and skin pigmentation of P. sphenops. A total of 45 molly fish (initial mean weight: ~1.5 g) were randomly distributed into three experimental groups (control, astaxanthin-supplemented, and 5% Spirulina-supplemented diets), with three replicates per treatment (10 fish per replicate). The fish were reared in controlled glass aquaria at 27°C. Growth performance metrics—including final weight, weight gain, total length, daily weight gain, specific growth rate (SGR), and feed conversion ratio (FCR)—were calculated. Skin pigmentation was quantified using a spectrophotometer based on the CIELAB color space (L*, a*, and b*). Multivariate statistical analysis, including non-metric multidimensional scaling (nMDS), was performed using PRIMER v6 software. The results revealed a clear segregation among the experimental groups based on the combined growth and color indices (2D Stress = 0.000). The Spirulina treatment exhibited the most significant enhancement in growth performance, resulting in superior final weight, length increment, SGR, and FCR compared to the control group. Conversely, the astaxanthin treatment exerted the most pronounced effect on coloration, leading to significant increases in redness (a*), yellowness (b*), and overall color brightness. The control group displayed the lowest values across all growth and pigmentation parameters. In conclusion, while Spirulina proved to be an effective supplement for stimulating growth due to its high nutritional value, astaxanthin was superior in enhancing skin coloration. These findings suggest that incorporating these supplements, particularly in combination, could serve as an effective strategy to simultaneously optimize growth and aesthetic quality in ornamental fish production.