<b>Effect of Enriching Commercial Feed Enrichment with Marine Fish Oil on Morphometric Characteristic and Growth of Mahseer, </b><b>Tor douronensis</b><b> Fry.</b>

This study aimed to determine the effect of feeds supplemented with yellowfin tuna oil (TFO), sardine oil (BFO), squid oil (SFO), and a control feed (CFO), each at 5 g/100 g of feed, on the biometric performance, including morphometric characteristics, length-weight relationship (LWR), and condition factors of Tor douronensis fry. Additionally, it tested the effects of these supplements on the growth performance of the fry. A total of 600 fry (initial weight: 721 mg, length: 32.40 mm) were divided into four treatment groups, each with three replicates. The fry were reared in 12 aquariums (28 L volume, 50 fry per aquarium) for 30 days. The results showed that the addition of marine fish oils significantly affected (P &lt; 0.05) morphometric characteristics, growth patterns, condition factors, and the biometric performance of Tor douronensis fry. Morphometric analysis indicated that the TFO group had the highest average total length, head length, and body height, while the CFO group had the lowest. The LWR coefficient b ranged from 2.821 to 3.169, with Tor douronensis fed with CFO displaying negative allometric growth (-) and those fed with TFO, BFO, and SFO showing positive allometric growth (+). The Fulton condition factor (Kc) ranged from 1.09 ± 0.10 to 1.40 ± 0.18, indicating morphological variation among fry fed with different diets. Fry fed with TFO showed a final weight gain of 36.75%, a mortality rate of 2.66%, and a feed efficiency of 83.24%. Based on these findings, TFO supplementation resulted the highest biometric and growth performance, the highest feed conversion efficiency, and lowest mortality rate in Tor douronensis fry.