Species diversification is one of the major approaches to increase the aquaculture production and selecting new species with a potential value for aquaculture has significant role for long term sustainability of the sector. One suitable potential candidate marine finfish species is the Indian pompano (Trachinotus mookalee). Breeding and seed production of the species has been studied well. However, many other aspects regarding nursery rearing and grow-out culture has not been studied yet. Therefore, the present study aimed to identify suitable feed for nursery rearing of the species.
A feeding trail was conducted to determine the suitable feed with different protein for juvenile of Indian pompano (Trachinotus mookalee) in confined environment. The study was also aimed to observe the effect of different feed on growth, body composition and changes in the expression of growth related genes such as growth hormone (GH) and Insulin like growth factor -I (IGF-I). Ten different feeds including 4 farm made feeds of different protein levels (35%, 40%, 45% and 50% crude protein); 3 commercial pelleted feeds of different protein (40%, 45%, 50% crude protein); fish meat; combination of 32% protein diet and fish meat at 1:1 and alternate feeding of 32% and 45% CP were used. Feeding trail was conducted in triplicates with total of 180 juveniles in each treatment for two months. Growth during nursery rearing was monitored in every fortnight. The body proximate composition were determined according to AOAC (AOAC, 1990), minerals and other elements were studied with the help of ICP-MS using AOAC 2012 method. The changes in mRNA levels of pituitary GH and hepatic IGF-I in response to differentiated growth due to different feeds were examined by a semi quantitative RT-PCR. Growth performance was evaluated with different growth parameters like % of weight gain, specific growth rate and feed conversion ratio (FCR). Growth parameters (%WG: 651±11.43, SG: 3.36±0.025, FCR: 1:1.985) were significantly (p<0.05) high for juveniles fed with commercial pelleted feed of 45% CP. Proximate composition analysis revealed that the juveniles fed with 45% showed significantly (p<0.05) lowest moisture (64.2±0.03) and highest protein (13.6±0.03) content. Total of 12 minerals were detected from samples tested, among which fish fed with formulated feed showed comparatively higher calcium content (7167 ppm). GHmRNA level in 45% commercial fed fish showed significantly higher expression rate. Hepatic IGF mRNA level is comparatively high in fish fed with commercial feed, whereas it is less in fish fed with only meat. The study illustrate that the Trachinotus mookalee juveniles fed with commercial diet containing 45% CP and 10% crude fat showed comparatively better growth performance and it may be considered as optimum feed for nursery rearing. The presence of essential mineral was high in fingerlings fed with commercial diets. This study has also observed that the GH & IGF-I gene expression, but the fold change in the gene expression did not observe correlation with the growth rate of the fish.