~ 1120 ~ Journal of Entomology and Zoology Studies 2021; 9(2): 1120-1123 E-ISSN: 2320-7078 P-ISSN: 2349-6800 www.entomoljournal.com JEZS 2021; 9(2): 1120-1123 © 2021 JEZS Received: 11-01-2021 Accepted: 15-02-2021 NN Pandey Principal Scientist (Aquaculture) ICAR- Directorate of Coldwater Fisheries Research, Bhimtal, Uttarakhand, India Bipin Kumar Vishwakarma Research Scholar, Zoology Department, DSB Campus, Kumaun University, Nainital, Uttarakhand, India Sheetal Sharma Research Scholar, Zoology Department, DSB Campus, Kumaun University, Nainital, Uttarakhand, India Santosh Kumar Technical Officer, ICAR- Directorate of Coldwater Fisheries Research, Bhimtal, Uttarakhand, India Corresponding Author: NN Pandey Principal Scientist (Aquaculture) ICAR- Directorate of Coldwater Fisheries Research, Bhimtal, Uttarakhand, India Comparative growth performance of diploids and triploids rainbow trout ( Oncorhynchus mykiss ) NN Pandey, Bipin Kumar Vishwakarma, Sheetal Sharma and Santosh Kumar Abstract Due to extra genetic material, triploid fish remain more heterozygous and suppose to be useful for increasing growth. A field study of 6 months was conducted to evaluate the growth performance of the diploid and triploid Oncorhynchus mykiss, which is one of the candidate fish for coldwater aquaculture in Himalayan region. Triploids were produced by pressure shock after post fertilization of eggs. The control group of diploids was observed for final body length and weight from the range of 32.9±0.83mm to 33.0±0.84 mm (0.89±0.083g to 0.91±0.081g), while treated triploids were observed as 42.8±0.79 to 43.25±0.77 mm (1.05±0.033 to 1.07±0.033 g). Observed data showed a significant difference (p<0.05) with 17.58% higher growth in triploids over diploids. Survival rate was in the range of 94-96% without any significant difference in both the groups. Study showed feasibility for achieving better growth of this fish in captive rearing with triploids. Keywords: Oncorhynchus mykiss, triploidy, heterozygous, post fertilization Introduction The rainbow trout is a prominent coldwater fish classified as Oncorhynchus mykiss and belongs to the family Salmonidae. It is recognized as the most widely farmed trout in the world and is popular as a sport fish and an experimental fish. It thrives in highly oxygenated freshwater with temperatures of 13-18 °C. These characteristics establish them as one of the most widely introduced and cultured fish across the globe and its farming is also prominent in the coldwater regions of India. Nevertheless, genetic fatigue, slow growth, early maturity and low productivity are limiting the expansion of trout production. A viable strategy that could overcome these farming constraints in large scale operation is the production of triploid fish that are sterile and more heterozygous. Such chromosomal manipulation and generation of polyploids is not exclusive to fish. Many plants used in modern agriculture are induced polyploids, selected to increase productivity associated with greater cell size or disease resistance. Triploid sterile fish are beneficial in aquaculture due to extra genetic material and more heterozygocity. In triploids, most of the anabolic energy is transferred to somatic growth [1] . Somatic growth is one of the most fundamental biological processes required for survival and thus has important fitness consequences, and growth rate is frequently used as an indicator of the capacity to acquire food resources [2, 3] . Triploidy is characterized by the change in normal diploid (2n) set of chromosomes to the state of triploid (3n) with an additional set of chromosome [4, 5, 6, 7, 8] . As compared to diploids, triploid cells are relatively big and will have a larger nucleus, however the ratio between the cytoplasm and the nucleus is constant [9, 10] . Increased cell size in triploids applies to all tissues and cells of the body. Several production related differences have been observed between triploid and diploid with respect to survival and hatchery performance [11] , growth and harvest quality [12, 13] , feeding behaviour [14] , nutrient requirements [15, 16] , body composition and energy reserves [17] . Based on the above reviews, the purpose of the study was to investigate the effect of triploidization on growth performance of triploid with their diploid counterparts in rainbow trout in field condition. Materials and Methods The study was carried out at ICAR-Directorate of Coldwater Fisheries Research (DCFR), situated at Bhimtal (Latitude 290 21’N, Longitude 790 34’E, 1370 masl), Uttarakhand. For the experiment purpose triploids were produced by pressure shock at 9500 psi for 5 min. after 24min. of post fertilization [18] and reared up to fingerling size.