Feeding habits and growth characteristics of cobia (Rachycentron canadum) larval and juvenile stages

Abstract

The feeding habits and growth of larvae and juveniles under artificial culture conditions were examined using the ecological method of simple random sampling to better understand the feeding characteristic of cobia (Rachycentron canadum) during the early development stage. The results showed that cobia larvae had a good foraging capability. After three days of the hatch (DAH), the larvae began feeding, and the feeding incidence was 70%. Feeding incidence was 100% in the case of juveniles. Feed intake of larvae and juveniles increases with increased body mass and could be expressed using the binomial equation (R² = 0.9188). The digestive tract fullness coefficient of 3–24-day-old larvae and juveniles fluctuated from 0.1% to 1.0%. The larvae and juveniles of cobia were satiated within 1 h. The digestion time of larvae to rotifers and copepods was between 0.5 and 1.5 h and 0.5–2 h, respectively, while that of juveniles was 1–3 h. The daily feeding rates of larvae and juveniles were 61.38% (5-day-old), 54.18% (10-day-old), and 24.85% (24-day-old), and could be used as a reference for the daily feeding (%) of both larval and juvenile stages of cobia. The feeding patterns of larvae and juveniles showed a circadian rhythm, suggesting that they were fed during the day. The average daily growth rate of full-length larvae and juveniles aged 3 to 24 days was 35.90%, with an average daily weight gain rate of 56.97%. The relationship among total length, body mass, and age were expressed using a quadratic equation of one variable (R² > 0.90) and a power function (R² > 0.90) for the regression equation of body mass and full length. This study provides useful insights on the early development stage, and a reference for large-scale production of cobia larvae and juveniles.