The blue swimming crab (Portunus pelagicus) is an important commercial species in Trang province, Southern Thailand. This study investigated the reproductive biology that supports the largest regional small-scale fishery of this species. A total of 217 male and 214 female crabs were randomly sampled from the catches of small-scale fishers, on a monthly basis from October 2010 to September 2011. All stages of gonad (testes and ovaries) development of crabs were observed throughout the year. The monthly mean values of Gonadosomatic Index (GSI) of male and female crabs ranged between 1.34 to 3.25, and 2.60 to 9.24%, respectively. Spawning season occurred twice a year, from December to February, and July to September. The sizes at 50% maturity (ICW50%) of male and females crabs were 8.02 and 8.09 cm, respectively. The fecundity of ovigerous crabs ranged widely from 98,627 to 1,319,480 eggs, with the average of 472,357 eggs. The fecundity of good breeder females ranged from 133,669 to 606,026 eggs.

จากการศึกษาประสิทธิภาพของลอบปูแบบเลือกจับโดยการใช้ตำแหน่งและรูปแบบช่องทางออกที่เหมาะสมสำหรับปูม้า (Portunus pelagicus Linnaeus, 1758) ในห้องปฏิบัติการ พบว่าตำแหน่งช่องทางออกที่เหมาะสมที่สุด คือ บริเวณด้านข้างตรงมุมล่างขอบลอบ โดยปูที่ออกตำแหน่งนี้คิดเป็น 86 เปอร์เซ็นต์ ส่วนรูปแบบช่องทางออกนั้นไม่มีความแตกต่างกัน และจากการศึกษาประสิทธิภาพของเหยื่อ 3 ชนิด ได้แก่ หอยแมลงภู่ ปลาสด และปลาหมักอ้อย ในหระหว่างเดือนพฤษภาคม - เดือนสิงหาคม 2546 บริเวณอ่าวศรีราชา จังหวัดชลบุรี ...

Information about reproductive biology is significantly needed in management of blue swimming crab (Portunus pelagicus) fishery. This research informs spatial and temporal sex ratio, gonadal development, gonado somatic index (GSI) and first size sexual maturity of male and female crab, as well as crab spawning season in Lasongko Bay, Southeast Sulawesi. Crab collection were conducted with gillnet in five different types of habitat. Gonadal development of crab was examined by their color and morphological characters. Sex ratio was analyzed of χ 2 test, and gonadal development proportion of male and female crabs were described. Gonado somatic index (GSI) among stations were analyzed by one-way ANOVA and followed by Tukey's test. Sex ratio of crabs spatially and temporally of generally did not differ significantly from 1:1. Gonad developments of male and female crab were varied spatially and temporally. GSI at every gonad development stage of male and female crabs generally was not significantly different among stations. GSI of male crab was smaller than the female crab. The first sexual maturity size of male and female crabs were 109.8 mm carapace width (CW) and 115.7 mm CW, respectively. The crab spawned in Lasongko Bay the whole year, and three peaks of spawning season were detected.