Abstract

The greasyback shrimp (Metapenaeus ensis) was studied in My Thanh River in Soc Trang Province, in the coastal region of the Mekong Delta in 2010. The bag net was used in the study; it had conducted six rounds of sampling (February, April, June, August, October, and December) at six stations along 30 km of river from the estuary at 6 km intervals. Besides, survey data also involved 36 fishermen, who are operating the bag net. Results showed that M. ensis was caught year-round. Carapace length (CL) was in the range 14.0 to 35.5 mm, but only 8% of M. ensis were in the largest cohort (CL > 28.3 to 35.5 mm), which was observed in June to August, whereas 36% were in the smallest cohort (14.0 to 21.1 mm) in August to February. The remaining 56% of shrimp, with CL 21.2 to 28.3 mm, CL and yield showed very weak correlations with salinity, depth, and transparency (R² ranging from -0.036 to 0.36). Yield was affected by time of year (different months) and was higher in the rainy season than in the dry season (P < 0.05). However, it did not differ across the various localities along the river (P> 0.05). The proportion of females was affected by various stations along the river during the various seasons (P < 0.01).

Key words: Bag net, greasyback shrimp, Metapenaeus ensis, carapace length, My Thanh River, Mekong Delta.