Hematological Responses of Monopterus albus to Gradual Salinity Adaptation (0-15 ppt)

Abstract The Asian swamp eel ( Monopterus albus ) is increasingly in demand due to population growth and consumer preference. To enhance production, marginal ponds and aquaculture intensification can be utilized. As a freshwater fish tolerant to salinity changes, this species shows potential for brackishwater aquaculture. This study examined the hematological responses of M. albus to gradual salinity adaptation and identified its salinity tolerance limit. The 30-day experiment used 90 eels (50.3 ± 2.4 g) reared in recirculating tanks consisting of three tanks stocked with 30 eels each (3 eels per replicate), with salinity increased by 1 ppt every two days from 0 to 15 ppt. From each tank, three eels were randomly sampled at each salinity increment for blood analysis. Blood was sampled for hematological and glucose analyses, while survival rate (SR) was recorded. Hematological parameters and glucose remained stable up to 12 ppt, but salinity above 12 ppt elevated glucose and reduced SR. At ≤12 ppt, hematological values w ere: erythrocytes 1.35–2.34 ×10 6 cells/mm 3 , hematocrit 20.7–28.7%, leukocytes 3.26–5.32 ×10 4 cells/mm 3 , hemoglobin 12.7–17.9 g/dL, glucose 26.7–47.7 mg/dL, and SR 66–100%. These results indicate that M. albus can physiologically adapt to 1–12 ppt, suggesting its culture potential in low-salinity brackishwater. Water quality (temperature, pH, DO) remained within optimal ranges.