University of Hawaiʻi at Mānoa

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    Identification and characterization of pathogenic <em>Aeromonas hydrophila</em> isolated from clinically diseased Chinese rice-field eel, <em>Monopterus albus</em>

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    Aeromonas hydrophila is recognized as a prevalent pathogenic bacterium in aquaculture. An outbreak of a disease characterized by a high mortality rate has been reported at a Chinese rice-field fish farm (Monopterus albus) located in Hubei Province. This study isolated a causative A. hydrophila strain (YFI-C1) in diseased Monopterus albus through bacterial isolation and subsequent morphological, physiological, biochemical, evolutionary and molecular biology analysis. Ten virulence genes, including those that encode cytotoxic enterotoxins (act and alt), a quorum sensing-controlled virulence factor (LuxS), a temperature-sensitive protease (eprCAI), serine proteinase (ser), haemolysin-aerolysin (aeraA), nuclease (nuc), hemolysin (hlyA), lipase (lip), flagellin (fla) have been shown to be responsible for YFI-C1's pathogenicity. An artificial infection was utilized to evaluate the pathogenicity of YFI-C1, with a median lethal dose (LD50) of 1 × 106 colony forming units (CFU)/mL. The Kirby-Bauer test was used to measure YFI-C1's sensitivity to ten antibiotics. According to the findings, YFI-C1 was resistant to Cefothiophene but extremely susceptible to six antibiotics: Ciprofloxacin, Trimethoprim-sulfamethoxazole, Doxycycline, Enrofloxacin, Compound sulfamethoxazoles, and Flufenicol. The results of this study offer valuable insights for future research on bacterial disease prevention and treatment in Monopterus albus

    Assessment of Indigenous Feed Ingredients on Growth and Feed Utilization Efficiency in Juvenile Milkfish (<em>Chanos chanos</em> Forsskål, 1775)

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    This study aimed to assess the feasibility of utilizing indigenous feed ingredients for milkfish (Chanos chanos Forsskål 1775) aquaculture. Nine different feed treatments were tested: taro, golden apple snail, azolla plant, blood meal, cacao pod, banana stem, copra meal, soybean meal, and a control. We used 15 juvenile milkfish (initial weights=6.4-7.4 g; initial lengths=5.3-5.7 cm) cultured in 80 L tanks and replicated three times to assess their growth and feed utilization. After 60 days of culture, copra meal and Azolla attained 23.0 g and 21.8 g, which were higher compared to the other treatments. This was followed by taro (18.9 g), bloodmeal (18.4 g), golden apple snail (18.2 g), control (18.2 g), cacao pod (18.2 g), soybean treatments (17.5 g), and lastly banana stem (16.1 g). Comparison of the initial length and weight of the treatments versus their final values during the 60 days of culture showed differences (length: t=20.0, p=0.0001, df=16; weight: t=16.5, p=0.0001, df=16) but none between the nine treatments (p\>0.05). In terms of average daily weight gain, copra meal gained faster (0.34 g), followed by Azolla (0.24 g), and then the control (0.22 g) and bloodmeal (0.19 g) with banana stem the last (0.15 g). While in terms of feed conversion ratio (FCR), copra meal (1.1), azolla (1.3), taro (1.5) and the control (1.5) had the lowest FCR values; banana stem (1.9) and soybean meal treatments (2.0) had the highest. Fulton's condition factor showed that these four treatments (taro=1; Azolla=1.2; copra meal=1.2; control=1.2) were closest to 1, signifying a healthy condition. The gonadosomatic index (GSI=0.005) and hepatosomatic index (HSI=0.03) values were consistent in the various treatments, showing no adverse effects suffered during the period of culture. The alternative feeds can be used in milkfish aquaculture to reduce the cost of operation

    Puka Puka Parade 2025 - Volume 80, Number 10

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