Reproduction, growth, population structure, and size at sexual maturity of the shiba shrimp, Metapenaeus joyneri were investigated in the western coast of Korea, Yellow Sea, from April 1994 to November 1995. The spawning season was June–August with peaks in July. Inseminated shrimp appeared from June to August, and the recruitment to the fished population took place in August. This shrimp shows a one-year life cycle with a single spawning season. Size at 50% sexual maturity (CL₅₀), determined from both mature females and inseminated females, was 19.6 mm and 20.4 mm CL, respectively. The smallest mature female found was 19 mm CL. Fecundity was directly proportional to the size of the female, with clutch sizes varying from 73,185 ova in the smallest female to 206,131 ova in the largest. Diameters of ova ranged from 220 μm to 340 μm. Size distribution of the population was similar in both years of the study. Shrimps were not caught within the studied area during winter (December–March), indicating that the shrimp migrated outside the range of the fishery or were not catchable at this time. Growth was estimated by the modified von Bertalanffy growth function incorporating seasonal variation in growth. In both years, females (K = 1.22 year⁻¹ and L_∞ = 34.7 mm CL) grew faster and reached a larger size at the same age than males (K = 1.02 year⁻¹ and L_∞ = 29.0 mm CL). The result is supported by differences in growth performance indices (ϕ′) between females and males.